Fresh Fizz Posted March 10, 2008 Report Share Posted March 10, 2008 I really think though I am reaching the end of my tether with my present trials and mostly errors with the switching. No matter how clever I get with the switching schematics it does not seem to solve the problem. Everything is of course switched simultaneously but I am not at all sure if this wouldn't only delay the "off clunk" (sounds like a guitar amp being turned off by the way). Maybe it's best to take a closer examination of figure 11 of patent 5932827. For the switching of the pickups and driver when used as pickup fets are being used. Notice the middle gate, neck gate, bridge gate filter. The make use of RC filters. The cap is charged and decharged smoothly through the resistor. The mosfet pair is not switched on and off. There is allways voltage across the mosfets even with the output jack disconnected! When the sustainer is off the comparator supply is switched off (V4 across C28). When switched off C28 will be decharged through the comparator, when switched on C28 will be charged smoothly through Q8. Fresh Fizz Link to comment Share on other sites More sharing options...
psw Posted March 10, 2008 Author Report Share Posted March 10, 2008 Maybe it's best to take a closer examination of figure 11 of patent 5932827. Well, you do realize that electronic schematics are a foreign language to me, I can only pass for very basic stuff. Of course I have looked at these a long while back, and if you guys will hold my hands, possibly for mutual benefit to understand them a little better...I will be all eyes and ears... Firstly, I don't know if this is really the guts of the commercial sustainer, but it is a good guide. For instance, this particular patent is for a mid pickup driver that never went into production and no one has ever seen. The possibility of it working though is pretty great as Dizzy was able to replicate it near enough to work...one does wonder why it never was produced though as the mid pickup would seem to be the most "expendable. Also, dizzy was able to use either and the the neck and bridge pickups for different effects (see the sustainer sound thread link in my sig to hear more on this DIY version). However...I have taken the first steps back with the patents, specifically this one, but if I am going back down this road, I have a mind to check the others too for ideas as it is specifically the switch pop question that is of concern to me...at this stage I intend to stick to my design ideas and linear amps as I am pleased with the performance and concept...it is that final switching execution that is letting the whole thing down IMHO...grrr So, on your advice I have printed out all 4 pages of figure 11. For other that follow and for reference, these are sheets 17,18,19 & 20 of the 28 patent drawings. If you are using alternatiff, these can be printed out very easily a page at a time. If useful, I will even scan them and post the relevant parts or the whole 4 pages. Parts of the circuit are encircled by dotted lines and labeled. Sheet 17 You have the bridge and neck pickup, each have a buffer and a "gate filter" (?) circuit. There is a bridge EQ and neck EQ and most interesting, a floating ground supply (?). This last was perhaps something I was trying to describe to isolate the shared grounds between pickups and drivers that may be some source of distortion or fizz besides EMI causes. This patent describes a mid driver so presumably the neck and bridge pickups are conventional, the buffering perhaps a general "active circuit" and eq, not sure why they need that...perhaps the floating ground is simply to power all these opamps...any ideas on this? Sheet 18 This shows the neck and bridge pickups going into a "drive current limiter" and a "current source amplifier". The middle bi-lateral driver is on the top right and the drive control below. There is a lsit of the op-amps, but as yet I can't seem to find op-amp IRF7107 on the circuit...perhaps I am missing something, it also refers to figure 11b...is there more? According to this IRF 7170 these are surface mount switching mosFET's so perhaps these are the two next to the driver and are a part of the d-class system described by curtisa and fizz. Sheet 19 This has a low noise preamp and below a momentary "on-off switch" and a "comparator supply" block linked to this. Sheet 20 This shows the tne and volume controls and output jack, battery etc. The lower part has a transistorized "battery supply" block, there is a small "pickup combiner" circuit block at the top, a large central "pickup selector logic" block in the middle and a middle gate filter at the end...a single lead goes to a cryptic label on/off on the lower right. Ok...I described these pages so we can all refer to them. It does illustrate the complexity of the sustainiac ap[proach and something I have steadfastly tried to avoid in all of my work. They have a lot of op-amps in this device, not to mention the other stuff, and if they are using SMD's (why wouldn't they) the circuit is very big in reality. Especially compared to mine which does in fact work, switching problems not withstanding. However, there may be something in there that could help me solve the problems I describe, but I am still no wiser as to what they are! If those studying these patents at this time could point me to the appropriate parts and explain them to me a little, I'd be most appreciative. I see a lot of things in there that I have suggested in my own way and asked if they would help...active buffering, floating grounds, etc...but nothing specific. A lot of the whole thing is a mystery, and looking again, where is the phase compensation circuitry so central to their other and most other patents? So...perhaps my eyes just gloss over when I see this, 28 pages of drawings, 4 pages of schematic plus a bunch more of supporting schematics. Surely it can be done easier simpler smaller and cheaper than this...oh, hang on, that's where I started from. For the switching of the pickups and driver when used as pickup fets are being used. Notice the middle gate, neck gate, bridge gate filter. The make use of RC filters. The cap is charged and decharged smoothly through the resistor. Ok...I see this, can yoiu explain how these work, R2 and R3 are sizable resitors...I don't understand quite how this works. the buffers seem to feed a pair of FETs. 123&4 I assume are the selector perhaps, the middle gate filter is different again(?)...what exactly are they filtering? These are some kind of trigger for the FET switching of the neck and bridge pickups I resume, so what is thir effect, to delay switching back on and so avoiding the pop? Granted, I have not read the many pages of descriptions in patent speak lately or in this quick servey, but I still feel I will need to be guided in this. I still think also that we have not adequately described exactly what the cause of the problem is. I am not sure as to how these fet switches address it either. I do note that there seems to be very little that suggests clipping preamps or seeking distortion...in fact there seems to be great lengths to ensure that the signal is filtered as much as possible... I will seek out a few others, perhaps the older rose, et al patents or the fernandes ones might give me a better idea of how they approached this from a more conventional (not a mid driver) approach. It was only after I saw all these patents and fretted over it with LK in the first dozen pages or so of this thread (I actually have a folder here of them all somewhere, printed out...about 2" thick!) that I put it aside with his encouragement. It was from this point and concentrating on driver designs married to simple amplifier circuits that significant headway was made. I'd be happy to pinch ideas and strategies from the patents to solve specific problems, but I think the whole thing is overly complicated. Perhaps it needs to be, in which case, buy a sustainer as I doubt you could replicate it as well. But, my whole reason for pursuing this with such tenacity has been to reduce it to it's essence. I must admit I got side tracked by the whole HEX system, but this was very much influenced by the issues you guys are pursuing now...EMI reducing designs at all costs. The HEX devices were very low in EMI but not all that practical to make. In simple terms one could see what the bi-lateral was aiming to do (send the EMI across the strings) and then take it to it's logical conclusion...a driver for each string. Proud of what I achieved in even being able to make working prototypes of these, they weren't startling better nor addressed some of the more fundamental issues still at large. I bet had they would have clicked and popped in switching just the same if I had continued along that path. Anyway...it's late and I'm tired and patents do not make good bed time reading. My advice, and I intend to take it, is to seek out other patents before and after this particular one to get a broader picture and ideas. There are many ways to achieve results with this technology, I am trying to find the simple path, 4 pages of schematics seems a little excessive for me given the principle of the device itself is so simple! pete Link to comment Share on other sites More sharing options...
psw Posted March 10, 2008 Author Report Share Posted March 10, 2008 Quick note...perhaps people may wish to look back to sustainiac's patent 5,070,759 link a bit cheeky linking to brook's infinite guitar that predated and inspired it, but not given the credit. They speak of prior arts and of the device in a simpler way than the later patent referenced. I was also looking at the rose patent, lots of phase compensation etc... All in all, very little detail unearthed so far as to the actual implementation into a guitar without switching noise. A lot is made of the deficiencies and means to which they compensate for shifting impedances. After all this time, I think that maybe col is right, perhaps I have a design that operates pretty much in resistance and impedance is not so much of an issue. It has been a long time since I have had trouble driving high strings for instance. If people want to go on a treasure hunt, reference one of these patents and then use the referenced by/cited by hyperlinks to uncover similar. You will need to do this on everyone to get a fairly exausted overview...there are a lot of related and relevant patents going back to before 1900 and a lot of familiar companies behind the names of the inventors that may surprise people (roiland for instance I spyed today) but never had any product that I know about. It can be addictive, but I fail to see a direct solution...or perhaps I am blinded by the rest of the complications...I have a hard time accepting that it has to be this complicated...I'd like to know what others think, am I being too simplistic and idealistic to be successful in this quest. Results seem to suggest otherwise...it definitely is working, it simply wont easily turn on without a click or thwack...more precisely, off!!! I tried snipping wires to see if I could isolate the problem...but it is tricky and there seems to be multiple types of clicks...sharp little pings when bridge pickup is selected, sometimes none at all (when the device is sustaining in bridge pup selection) to a thwack when neck pickup is returned to. Obviously, cutting out the pickups completely, leaving only the bridge pickup completely solves the problem....hmmm I must be missing some obvious strategy me thinks...if I could work out "a way" to do it, I could simplify that perhaps, but working up from no pickups to clicking pickups is not working for me.... pete Link to comment Share on other sites More sharing options...
col Posted March 10, 2008 Report Share Posted March 10, 2008 ...For instance, this particular patent is for a mid pickup driver that never went into production and no one has ever seen. The possibility of it working though is pretty great as Dizzy was able to replicate it near enough to work...one does wonder why it never was produced though as the mid pickup would seem to be the most "expendable. Also, dizzy was able to use either and the the neck and bridge pickups for different effects (see the sustainer sound thread link in my sig to hear more on this DIY version). My guess is that it will work in the mid position on some guitars. However, restricting it to neck position with bridge driver made it work on many times more different guitars, so for commercial reasons, they decide to go down that route. ...and most interesting, a floating ground supply (?)......perhaps the floating ground is simply to power all these opamps...any ideas on this? I've uploaded a diagram for this before Op-amps are designed to use a positive supply and a negative supply with ground at zero. we are using 'single-ended' supply, so we only have zero and positive (+9v). To allow the use of op-amps, we pretend that 9v is +4.5, 0v is -4.5, and we create a 'virtual ground' at 4.5v that we pretent is 0v. The simplest way to do that is to use two equal value resistors as a potential divider. Unfortunately, when there are more components using it and therefor higher loading on this virtual ground, the simple potential divider doesn't work, because to stop the virtual ground being pulled out of whack, the resistors have to be so low that we drain off lots of current from the battery... the solution is to buffer the potential divider with an op-amp. Its a simple and standard technique used in many circuits.. look at the schematics for my two circuits and you will see the same thing at the top/left of the diagram. Sheet 18 but as yet I can't seem to find op-amp IRF7107 on the circuit...perhaps I am missing something... IRF7107 is a single package containing two complimentary power MOSFETS - the output transistors. ...the circuit is very big in reality. Especially compared to mine which does in fact work, switching problems not withstanding. Quite a lot of their circuit is specifically dealing with the switching. If you were to remove all the switching stuff, and live with the noise of mechanical switching (assuming that the amp can still survive?!), the circuitry would probably be less than half the size. you could probably remove the pickup input filtering and certainly scrap the preamp because thats only needed for using the driver as a pickup. Basically, if you strip is all down for 1 pickup 1 driver with mechanical switching, it's going to be similar in size to my current circuit - not tiny, but certainly manageable, even without SMD The fancy switching is a combination of those FETs with gate filters, all those funny looking logic gates, and the multi stage power supply circuitry, If you were to attempt something similar with pin through hole sizes components, your circuit would get a LOT larger! It still might be the simplest and most compact solution to the switching issues you have. cheers Col Link to comment Share on other sites More sharing options...
Fresh Fizz Posted March 10, 2008 Report Share Posted March 10, 2008 Ok...I see this, can yoiu explain how these work, R2 and R3 are sizable resitors...I don't understand quite how this works. the buffers seem to feed a pair of FETs. 123&4 I assume are the selector perhaps, the middle gate filter is different again(?)...what exactly are they filtering? These are some kind of trigger for the FET switching of the neck and bridge pickups I resume, so what is thir effect, to delay switching back on and so avoiding the pop? That's exactly what it has been designed for, to avoid switching noise. If we look at Q1 it's source is connected with the output of IC1 which has the same potential as V1. That's the floating ground, half of the available voltage, 4.5 volt. You could see the floating ground as bias for the IC. Thanks to this bias the IC can deal with the positive as well as the negative half of an AC signal. The gate receives it signal from 3 of U5a. It's some sort of binary logic so the output of U5a can be low (<4.5 volt Q1 open) or high (>4,5 volt Q1 closed). The point I was trying to make is that the best way to proceed is to go through the patents and figure out how the switching functions. Maybe you're pushing yourself too hard and are you trying something that even the sustainiac guys couldn't solve! There must be a schematic somewhere that solves your switching problems. FF Link to comment Share on other sites More sharing options...
psw Posted March 10, 2008 Author Report Share Posted March 10, 2008 Stand by for convoluted post explaining how I am reading this to aid people to explain where I may be misinterpreting things....here goes... The point I was trying to make is that the best way to proceed is to go through the patents and figure out how the switching functions. Maybe you're pushing yourself too hard and are you trying something that even the sustainiac guys couldn't solve! There must be a schematic somewhere that solves your switching problems. Quite right, I did do quite a few active switching schemes some of which were discussed here, what they lacked was any real delays or sequential switching. Ok, I understand now, the floating supply is a fancy voltage divider for all these op-amps...yes I remember you mentioning it, but the term escaped me col, I brought it up previously in relation to the potential for isolating the ground to avoid fizz and possible switch noise through this shared ground rail in typical simple linear circuits such as the F/R or mine. Maybe it helps, maybe it doesn't... I quite agree, any solution would be a start. But what I lack is an understanding of how this circuit is dealing with it. I take it hten that the FET switches are used to produce a sequential start up and shut down procedure. What is the sequence then? The major value difference is the 01uF cap in the "bridge gate filter" and the .01uF cap in the "neck gate filter". I also note that they use two FET's so appear to completely isolate the pickups (both ground and hot) when triggered. What are the numbers 1,2,3 & 4 in sqaures going to...the selector in some way to trigger these gates I assume. WRONG = (* answered this myself I think, see top of sheet 20) Again, I am not sure of the functions of the next blocks...the current source amplifier is the d-class switching amplifier for the driver I assume, the drive current limiter, some kind of AGC? Does the drive knob VR1 then control the threshold of this limiter? Probably not a part of the switching solution in any case. Moving on, the "low noise preamp" on sheet 19 is entered by MPU2...I am a little lost, let's see. This preamp is perhaps to turn the middle driver into an active pickup. I appears the signal is going from right to left ending in MPU2. Below this is a momentary switch on off flip flop, the adjoining comparator block I assume is producing control voltages V3 and V4...am I on the right track? So now we get to the last page, sheet 20 predominated by the "pickup selector logic" block. Ah...I see, reenter 1,2,3 & 4 from the first page!!! * 1 & 2 are the bridge and neck pickup hot signal connections, 3 & 4 the control gate, switching connections...right. they run directly to the controls and output via a simple "pickup combiner" block. Can someone explain this little element, is this something to do with the now active nature of the pickups that they need this. I take it that this is not a part of the "switching solution" so much? Ah, I see the middle pickup is also connected via a FET switch triggered by another "gate filter" block with values similar to the neck pickup gate. So, sheet 20 is the switching guts, the pickups have multiple "gate" FET switches and the selector and controls appear on the left side. The selector is grounded, sending the gates (U5) low and thus triggering them, is this right. U5 is a NAND gate 4011, U6 is a NOR gate 4001 and controls the middle pickup switching from driver to pickup I assume with an on-off voltage from the lower right...ah, this is generated from the on-off block previously and had exited from the left...ok. 3 & 4 are the control voltages for the "filter" pickup gates from the first page. Basically (yeah basic, for you guys but bear with me ) , an electronic version of the selector. With some more grappling I will get the hang of it's logic I guess, all the values of resistors seem to be the same (4.7M) and there are no delaying caps, so these would appear to be straight logic switches. --------------- In summary, as far as the switching goes, it would appear it is a combination of the last page (sheet 20) where the selector functions are performed by low trigger voltages from the selector switch that in turn trigger the chip gates of the 4011 (U5) and so selecting the pickups. I don't yet understand U6 but it is somehow controlling the middle pickup/driver functions. (What is V3A by the way...is this the same as V3, the positive from the floating supply? What happened to V4 from the "comparator supply" in the on-off block on sheet 19?) Ok...so it would seem that the 3 pickup "gate filters" are the crucial elements in the pop suppression of the circuit. They create delays and so a sequential switch on and off procedure. To me, it would seem the values of C20 in the "middle gate filter" (sheet 20) and C4 in the neck gate filter (both 0.01uF) suggest these switch together. The corresponding C3 at 01uF is bigger, or is this a misprint. Is this the delaying part, the difference between 0.01uF and 1 uf in discharging and so triggering the gates? C18 in the on/off mid-driver/pickup gate 0.1uF seems to indicate a different delay, is this where the secret lies. This is enough for one sitting for me, perhaps someone else would like to layman-ize the sequence of the critical elements of these switching gates, in particular the on off sequence of events. I imagine that we can assume that a lot of the logic gates in the "pickup selector logic" block are there to enable the selector to operate electronic switches. The 3 pcikup "gate fliers" create the delays. I am not understanding quite what happens when the control voltage at on/off is applied. It would seem that U6C and U6D simply take it out of selection...does it replace it with neck and bridge if the selector is in this position? The "middle gate filter" has an additional diode and cap (C19) is this the critical delay, does the diode effect the delay going on and going off in some way? The "current source amplifier" seems to be hearing both the middle and bridge pickups and the purpose of the "EQ" blocks is to condition the signals for this purpose...is that the idea? So, as far as switching goes...if someone could read this and translate it and describe the sequence of events that occur when the on-off voltage is applied that enables it to do this without clicking or popping. Is the middle pickup taken out by the selector logic and replaced in all positions by the neck and middle when activated, is that the idea? If there is back EMF in the driver/middle pickup...where does this discharge to when the thing is turned off? what is the sequence that prevents that, is a simple delay enough to stop it, or would a delay, simply delay the noise??? Perhaps the dual opposing coils of the bi-lateral, or any such driver does not produce such EMF and it is not really an issue. Perhaps it is a failure of my design that such EM forces are produced, perhaps a driver on a stacked coiled SC pickup is a solution and restriction on the design to create a similar effect/solution. Anyway, obviously the logic is alluding me, just woke up to this. Again, appreciate any help you may have to offer in understanding this. I am curious as to what people may make of the other patents also, do they simply ignore these issues of switching, making no mention of strategies to combat them? pete Link to comment Share on other sites More sharing options...
curtisa Posted March 10, 2008 Report Share Posted March 10, 2008 Edit: D'oh! Too many quotes! Quote (Pete): I take it hten that the FET switches are used to produce a sequential start up and shut down procedure. What is the sequence then? Looking at sheets 17 and 20, I don't think there is any sequence. The "gate filters" are just there to provide a quick fade up/fade down function to the gates of the FET's. The logic driving the gates is controlled by the selector switch, which if unfiltered, would cause pops in the signals as the FET's were turned off and on. The bridge and neck pickup gate filters have the same time constants, whereas the middle pickup/driver gate filter has a slighlty different time constant (long on fade up, short on fade down). There is also an additional filter shown at the bottom-right corner of sheet 20 that provides an additional cross-fade of the middle pickup output when the sustainer is turned on. Without analysing it closer it looks like when the sustainer is turned off and on everything starts simultaneously, but the delays from the time constants involved means that the driver supply, middle pickup output etc all finish their switching operations at differen't times. Quote (Pete): Again, I am not sure of the functions of the next blocks...the current source amplifier is the d-class switching amplifier for the driver I assume, the drive current limiter, some kind of AGC? Does the drive knob VR1 then control the threshold of this limiter? Probably not a part of the switching solution in any case. Yep, all correct. Quote (Pete): Moving on, the "low noise preamp" on sheet 19 is entered by MPU2...I am a little lost, let's see. This preamp is perhaps to turn the middle driver into an active pickup. I appears the signal is going from right to left ending in MPU2. Yup again. The driver is the middle pickup when used "backwards", but because of the lower number of turns the output of the driver is much lower than a normal guitar pickup would be, hence the requirement for a special low noise preamp on sheet 19 to boost it back up to more reasonable levels. Quote (Pete): Below this is a momentary switch on off flip flop, the adjoining comparator block I assume is producing control voltages V3 and V4...am I on the right track? Voltage V3 is always present - it's the battery supply that's turned on when you plug a lead into the guitar's output jack. V4 is the switched voltage going to the driver amp to start it up and shut it down when the flipflop is toggled. ...they run directly to the controls and output via a simple "pickup combiner" block. Can someone explain this little element, is this something to do with the now active nature of the pickups that they need this. I take it that this is not a part of the "switching solution" so much? It's just a common point for all the FET-switched ouputs of each pickup to be combined before they're sent to the volume and tone controls, and finally the output jack. No different to the "common" connection on a normal 5-way selector switch. The 22K resistors (R30, R31) are added to prevent the ouput of one pickup from trying to back-feed into any other pickup connected to the common point, not normally a problem with a passive pickup scheme, but can be with an active system like this one. So, sheet 20 is the switching guts, the pickups have multiple "gate" FET switches and the selector and controls appear on the left side. The selector is grounded, sending the gates (U5) low and thus triggering them, is this right. Mostly. The pickups have one FET each, plus the bridge and middle have an additional FET each to turn off the signal feeding the "EQ" sections - the EQ sections are only feeding the driver amp, so you need to switch them aswell when you've got the sustainer running and you're changing pickups at the same time. I don't yet understand U6 but it is somehow controlling the middle pickup/driver functions. You mean U6d (sheet 20)? It's turning the output of the middle pickup on and off when 1. used as a normal pickup and controlled by the pickup switch, and 2. when the sustainer is turned on the pickup output needs to be turned off. (What is V3A by the way...is this the same as V3, the positive from the floating supply? It's just a filtered version of V3. V3A is only used by the logic gates. Filtering this supply helps keep unwanted switching noise out of the V3 supply feeding the analog circuitry. Very common technique. What happened to V4 from the "comparator supply" in the on-off block on sheet 19? V4 is only used on sheet 18 to turn the drive circuit on and off. Note that the MOSFET's stay energised all the time (V2), but without any drive (V4 switched off) they'll stay cut off, not drawing any power. Probably helps control turn on/turn off noise. V4 is a bit like the "mute" function on the class-D chips. The 3 pcikup "gate fliers" create the delays. I am not understanding quite what happens when the control voltage at on/off is applied. It would seem that U6C and U6D simply take it out of selection...does it replace it with neck and bridge if the selector is in this position? With the pickup selector in the middle position and the sustainer "off", the outputs of U5a and U5b are "high", cutting off the signal from the Neck and Bridge pickups, and allowing the signal from the middle pickup through. With the pickup selector in the mid position and the sustainer turned "on", the voltage at pin 13 of U6d starts to rise. When it gets high enough the output of U6d goes high, fading down the middle pickup output; and the the outputs of U5a and U5b go low, fading up the bridge and neck pickups. So with sustainer off your pickup selector operates as bridge-middle-neck, and with sustainer on you have (mid sustainer+bridge)-(mid sustainer+bridge+neck)-(mid sustainer+neck). The "middle gate filter" has an additional diode and cap (C19) is this the critical delay, does the diode effect the delay going on and going off in some way? The diode allows the fade time constant on that gate to be quick in one direction, and slow in the other. The "current source amplifier" seems to be hearing both the middle and bridge pickups and the purpose of the "EQ" blocks is to condition the signals for this purpose...is that the idea? I think you mean bridge and neck. The current source amp only hears the pickups that are selected via FET's Q2 and Q3 (sheet 17). And yes, the EQ is used to condition the pickup signals for the driver. The bridge pickup looks like it's being band-passed at about 720Hz, (which seems odd, maybe it's more of an all-pass phase compensation circuit?...or just a typo!), and the neck pickup has a band-pass filter on it with some bass cut at 480Hz and a treble limit of 3.3KHz. If there is back EMF in the driver/middle pickup...where does this discharge to when the thing is turned off? what is the sequence that prevents that, is a simple delay enough to stop it, or would a delay, simply delay the noise??? Perhaps the dual opposing coils of the bi-lateral, or any such driver does not produce such EMF and it is not really an issue. Perhaps it is a failure of my design that such EM forces are produced, perhaps a driver on a stacked coiled SC pickup is a solution and restriction on the design to create a similar effect/solution. I think there's two things going for this system. One is the cross-faded signals and voltages created by the various filtered-gate FET's and transistors, and the other (unfortunately for our DIY sustainers!) is that the driver does not create a step-up transforming effect with any stacked pickup combos because the driver is the pickup. Link to comment Share on other sites More sharing options...
psw Posted March 11, 2008 Author Report Share Posted March 11, 2008 Ok...thanks curtisa, between my struggling and your elucidating, perhaps between us we are doing something that had to be done eventually and really come to grips with this patent. I would still encourage some looking into other patents, perhaps the earlier sustainiac ones, and to uncover something of what may be happening in the production, neck driver circuit (I suspect i is similar though...but what would I know). There are some important observations that could be of benefit and gives some renewed hope, along with some paper and pencil jottings this morning approaching it from the other direction and trying to work out how much "electronic" switching is really required and what kinds of delays are necessary. With a lot of futzing around, I have worked out ways of switching and bypassing very effectively and economically with passive mechanical switching. QUOTE ...they run directly to the controls and output via a simple "pickup combiner" block. Can someone explain this little element, is this something to do with the now active nature of the pickups that they need this. I take it that this is not a part of the "switching solution" so much? It's just a common point for all the FET-switched ouputs of each pickup to be combined before they're sent to the volume and tone controls, and finally the output jack. No different to the "common" connection on a normal 5-way selector switch. The 22K resistors (R30, R31) are added to prevent the ouput of one pickup from trying to back-feed into any other pickup connected to the common point, not normally a problem with a passive pickup scheme, but can be with an active system like this one. Hmmm...yes, not normally a problem, but when my circuit is on, the bridge pickup may well be buffered by the preamp and so effectively be active. Is it possible that this could add to noise. This is why I was wondering whether a buffer on the whole guitar would help in some way...or if noise was created by the switching off of this buffer, even if no gain is apparent when it is in operation...any thoughts? So with sustainer off your pickup selector operates as bridge-middle-neck, and with sustainer on you have (mid sustainer+bridge)-(mid sustainer+bridge+neck)-(mid sustainer+neck). Ok...so are positions 2 and 4 on a fiveway (neck/middle and middle/bridge) now N+B as well? I am guessing so. These combination positions have been causing me some problems and limiting what I can do with 5TDP selector passively. QUOTE The "middle gate filter" has an additional diode and cap (C19) is this the critical delay, does the diode effect the delay going on and going off in some way? The diode allows the fade time constant on that gate to be quick in one direction, and slow in the other. Aha...now I think the really pertinent part is being revealed and may be of use. I get very little to no on switch noise, the sequential cascade needs to be different in different directions and this little detail seems to provide some control over this. I think what I need to have happen is that the circuit power goes off but the bridge pickup remains connected for a little longer before coming out of bypass. You don't ever want the circuit on while the other pickups are in circuit. Also, a small delay could help in discharging the coils/s perhaps and stop the pop. So, for a little while after coming out of bypass, you want it to behave as a single bridge pickup guitar with nothing else connected. On turn on, you want an instant disengagement of the other pickups and connection to the bridge and perhaps a delay in the application of power to the circuit. With the parallel pickup/driver configuration, perhaps these will need to disengaged a little earlier before the pickup returns to passive pickup mode. Ideally, electronic switching to achieve this would sleep and no power required when the sustainer is off. The reason for this is so that the guitar will work as normal even if the battery were removed...it may not be possible, but it is an ideal! QUOTE What happened to V4 from the "comparator supply" in the on-off block on sheet 19? V4 is only used on sheet 18 to turn the drive circuit on and off. Note that the MOSFET's stay energised all the time (V2), but without any drive (V4 switched off) they'll stay cut off, not drawing any power. Probably helps control turn on/turn off noise. V4 is a bit like the "mute" function on the class-D chips. Ok...if you look again at the 2073 data sheet, there is a muting circuit drawn there...not an actual pin like modern d-class chips, but a simple add on all the same... Now the words "Probably helps control turn on/turn off noise. V4 is a bit like the "mute" function on the class-D chips" of course raises interest. I still have found though no switch noise from the circuit when used only with one pickup...so I am not sure, but does this not suggest that switch noise is not really related to the amp circuit powering up and down...or am I misunderstanding the symptoms as, with the neck pickup out of circuit, I don't hear the circuit shutdown noise at it's output until it is...is that the noise perhaps...it certainly sounds like a mini version of what happens when you turn off a guitar amp and get a speaker thump. Are there de-thumping circuits to prevent that in amps that could be applied here do you think? Again, perhaps some delays as suggested above may correct it...any thoughts? I think there's two things going for this system. One is the cross-faded signals and voltages created by the various filtered-gate FET's and transistors, and the other (unfortunately for our DIY sustainers!) is that the driver does not create a step-up transforming effect with any stacked pickup combos because the driver is the pickup. I think there are a few other things going for it too. Perhaps the bi-lateral driver is immune from back EMF due to the dual coil construction...or less so. I am thinking about the different effect stacked coils seemed to have in combination with a driver coil on top and sharing the core. Also, I was thinking, I don't know if my test guitar has rwrp pickup combinations with the middle and neck anymore (pickup changes)...however this is usual. I wonder if I could parallel both the middle neck and driver coils...what is that formula again for calculating the value. I was thinking that it appeared that the added pickup coil to the system did little to reduce the value, by adding the middle pickup, perhaps I could create an opposing back EMF to cancel out the other...of course, this would only probably work in position 2 where both are selected...grrrr So, maybe not. So...from all this...it would appear the most significant part of this schematic to do with avoiding noise is the delays within the middle pickup gate filter block and the use of the diode for instance to alter the response in switch on and switch off. If the other FET switching and selector logic is not crucial to this problem (as they all seem to switch simultaneously) then perhapos there is reason to hope for a solution that could run with traditional mechanical switches and use FET's to do switching related to the driver and power up and down sequences when running the device only...well, that would be the aim. It may not be that complicated if reduced to this block only. Anyway...must run...so much thanks for that post curtisa, much help. I will try and think out the sequence I would like to occur with the switching I seem to be able to achieve so far, and perhaps we could adopt this principle to the problem is some way. pete Edit: D'oh! Too many quotes! Don't you just hate that... Link to comment Share on other sites More sharing options...
curtisa Posted March 11, 2008 Report Share Posted March 11, 2008 Quote (Pete): Hmmm...yes, not normally a problem, but when my circuit is on, the bridge pickup may well be buffered by the preamp and so effectively be active. Is it possible that this could add to noise. This is why I was wondering whether a buffer on the whole guitar would help in some way...or if noise was created by the switching off of this buffer, even if no gain is apparent when it is in operation...any thoughts? No, I don't think in your application it's necessary. It's required in the sustainiac patent diagrams because they're buffering both neck and bridge PU's, using active FET switching, and when the sustainer is running you have the option of choosing the bridge and neck pickups together - there has to be a way of introducing some degree of isolation between the two active PU systems, and the 22K resistors do this nicely. In your case the idea is to only use the bridge PU as the active pickup while the sustainer is running, and disconnect any others from the system. With only 1 pickup active during sustainer operation there's no need to prevent cross feed, and hence no need to do resistive mixing. Quote (Pete):Ok...so are positions 2 and 4 on a fiveway (neck/middle and middle/bridge) now N+B as well? I am guessing so. These combination positions have been causing me some problems and limiting what I can do with 5TDP selector passively. I don't think the sustainer patent actually uses a 5-way switch. It's only shown as a 3-way switch on the diagrams. In normal pickup mode you don't get the option to do the usual bridge-middle middle-neck positions so it is a little limited in that respect. However the logic and FET switching circuitry will become quite a bit larger if you were to make the jump to 5-way switching, and you're left with two choices - with the sustainer active you either have to use the pickup selector with 3 "dead spots" (bridge-middle, middle, and middle-neck wouldn't be available as the driver has to be used); or provide extra multiple coiltap options to allow things like bridge humbucker, bridge coil tap+neck coil tap, neck parallel etc...The FET switching required would double and the logic would rapidly get out of control. Quote (Pete): Aha...now I think the really pertinent part is being revealed and may be of use. I get very little to no on switch noise, the sequential cascade needs to be different in different directions and this little detail seems to provide some control over this. More than likely, yes. I too get very little switch-on noise, it's the switch-off that's the problem for me. And I suspect that it's for the reasons I gave earlier. It's not a problem at switch-on because the LM386 takes a handful of milliseconds to become active, and the mechanical switch has taken care of the necessary bridge pickup selection/neck pickup bypass etc by the time the chip has become stable enough to pass signal to the driver. On switch-off however, the amp is the last thing to "die", not the first. And herein lieth the problem Quote (Pete): I think what I need to have happen is that the circuit power goes off but the bridge pickup remains connected for a little longer before coming out of bypass. You don't ever want the circuit on while the other pickups are in circuit. Also, a small delay could help in discharging the coils/s perhaps and stop the pop. So, for a little while after coming out of bypass, you want it to behave as a single bridge pickup guitar with nothing else connected. On turn on, you want an instant disengagement of the other pickups and connection to the bridge and perhaps a delay in the application of power to the circuit. I think what you really need is something that turns off the amp before it releases control of the driver, and then returns the guitar to normal configuration. Quote (Pete): Ok...if you look again at the 2073 data sheet, there is a muting circuit drawn there...not an actual pin like modern d-class chips, but a simple add on all the same... I think we're looking at different versions of the datasheet - I don't see anything like that on mine. Which one are you looking at? I still have found though no switch noise from the circuit when used only with one pickup...so I am not sure, but does this not suggest that switch noise is not really related to the amp circuit powering up and down...or am I misunderstanding the symptoms as, with the neck pickup out of circuit, I don't hear the circuit shutdown noise at it's output until it is...is that the noise perhaps... I think you will hear some switch-on/switch-off noise if you are running a perfect LM386 system, but probably only a tiny click. But the most significant cause of the switch-off thump at the moment is (I believe) the un-synchronised hard-switching of the amp and neck pickup. it certainly sounds like a mini version of what happens when you turn off a guitar amp and get a speaker thump. Are there de-thumping circuits to prevent that in amps that could be applied here do you think? Again, perhaps some delays as suggested above may correct it...any thoughts? De-thumping circuits in big amps work by disconnecting the speakers via a fast-acting relay. The thump still happens inside the amp, you just don't hear it. Not really practical in our sustainer system. I think there are a few other things going for it too. Perhaps the bi-lateral driver is immune from back EMF due to the dual coil construction...or less so. I am thinking about the different effect stacked coils seemed to have in combination with a driver coil on top and sharing the core. I suspect that the back EMF in the driver isn't the problem, it's the pickup winding that's the biggest offender. There may be a back EMF in the driver on switch-off, but it's probably quite small (low turns, low inductance, thus a small EMF). However, the coupling effect into the pickup winding will cause a tiny EMF spike into a massive EMF spike by way of the winding ratio between the driver and pickup windings - quite possibly hundreds of volts! And while this voltage may not be directly applied to the guitar circuitry during switch-off (the voltage will probably be slugged somewhat by the additional load imposed on it by the rest of the guitar system when everything is reconnected at switch-off), it will quite likely be induced and/or electrostatically coupled into surrounding circuitry (eg, nearby pickups, unshielded signal wires etc). I remember when I first built my sustainer, connecting my voltmeter across the pickup winding while the driver was active and I was seeing peaks of 100+ VAC as the guitar signal was being applied. I really hate to say this, but I think the stacked pickup/driver will always be troublesome because of this. Also, I was thinking, I don't know if my test guitar has rwrp pickup combinations with the middle and neck anymore (pickup changes)...however this is usual. I wonder if I could parallel both the middle neck and driver coils...what is that formula again for calculating the value. I was thinking that it appeared that the added pickup coil to the system did little to reduce the value, by adding the middle pickup, perhaps I could create an opposing back EMF to cancel out the other...of course, this would only probably work in position 2 where both are selected...grrrr So, maybe not. Probably a bit hit-and-miss. How do you ensure that the "anti-EMF" will be the exact opposite of the EMF generated at the point of reconnection for example? So...from all this...it would appear the most significant part of this schematic to do with avoiding noise is the delays within the middle pickup gate filter block and the use of the diode for instance to alter the response in switch on and switch off. If the other FET switching and selector logic is not crucial to this problem (as they all seem to switch simultaneously) then perhapos there is reason to hope for a solution that could run with traditional mechanical switches and use FET's to do switching related to the driver and power up and down sequences when running the device only...well, that would be the aim. It may not be that complicated if reduced to this block only. Yes, definitely the way forward. I really think the synchronised switching (and/or cross-fading) of the system is the biggest clue in making the scheme pop-free. Anyway...must run...so much thanks for that post curtisa, much help. I will try and think out the sequence I would like to occur with the switching I seem to be able to achieve so far, and perhaps we could adopt this principle to the problem is some way. Indeed, let's hope so! I hope I haven't come across as too negative about the existing DIY sustainer system in recent posts, I'm only throwing my hat in the ring and trying to help iron out the bugs. And finally, to raise the tone a little out of geekspeak, some DIY porn: The Current Sustainer Build (Part 1) 1. The original humbucker pickup 2. Humbucker in pieces 3. Core removed from first bobbin 4. Old pickup winding wire removed 5. Bobbin end separated 6. Bobbin marked for shortening 7. Shortened bobbin ready for glueing 8. Bobbins glued and drying 9. Donor-transformer laminations being removed 10. Transformer laminations marked for cutting 11. Laminations cut from "E" section 12. Laminations cut for one bobbin 13. Laminations being filed to same length 14. Test fitting laminations in bobbins 15. Laminations re-varnished to maintain conductive isolation 16. Copper foil removed from cable offcut 17. Winding the bobbin coil 18. Almost done winding 19. Winding finished 20. Bobbin tape applied 21. Laminations fitted 22. All done! To be continued... Link to comment Share on other sites More sharing options...
psw Posted March 11, 2008 Author Report Share Posted March 11, 2008 Lovely... I hope I haven't come across as too negative about the existing DIY sustainer system in recent posts, I'm only throwing my hat in the ring and trying to help iron out the bugs. No, it is invaluable. I do feel very despondent about this issue, but then I have hit walls that have crumbled before. This device is presently working exceptionally well and I am unlikely to give up seeking a solution just yet when it is so close to working in a practical way. Unfortunately, my skills are limited in this regard but I am grateful that you have spent the time to actually look into the reasons of the problem and not dismiss it. I do believe that a guitar without a neck pickup is tremendously limited despite the sustainer for the kind of things I want from it at least. Perhaps this is the limit of the DIY device, but that would be a shame. I find it hard to believe that some way of organizing a noise free switching is impossible, but perhaps you are right. Perhaps a dual coil driver has less of this effect and I can apply my designs in this area and see if that helps at all as far as switch noise. The single coil sized driver was something I was particularly fond of. Perhaps it would work on a stacked coil...the only ones I have handy are stacked coil in bridge sizes and neither will fit my standard coil, nor fit without being angled as on a bridge strat with the string spread. I may be able to get something and try that out as there was a noticeable difference in secondary coil effects and it may have had, if properly tested, an impact on back EMF effects too. I guess another idea would be to explore the mid-driver thing again...however after my last experience, I suspect it may require the revisiting of the HEX ideas to maximise the EMI reduction and to provide enough "throw" that the driver needs to be excessively close to the strings. I guess the other thing is that so much work has gone into this to get it this far that it would be a shame to throw it all away over a switching issue. If it is that the ultra thin driver is working largely on resistance, then that is some achievement. I could conceivably take it off the pickup, but it would still be very close (even if not sharing a core) and I suspect that there would still be some problems with this proximity. A bi-lateral driver would greatly interfere with a nearby pickup I would think as the polarity crosses over between string sets and is likely to reinforce one set as it detracts from another...it would also likely be magnetically coupled anyway and produce some noise similar to that I already experience. Oh well...perhaps I will sit back and see how yours goes...any chance of testing it in a mid position? If the thing could operate with either/and neck and bridge pickups, sophisticated switching as with the sustainiac would seem obsolete and the driver could be designed and remain with this function. As ambitious as this might sound, this is exactly what Dizzy achieved with his bi-lateral driver and circuit and even got unusual effects depending on the pickup combinations (harmonic flavours for instance) and the proof is in the hearing (see the sustainer sounds thread). I suspect that with out a dual use driver as pickup the switching would be considerably easier if not possible passively (no bypassing required) and this was alway the aim of my adventures in mid driver construction...perhaps I will be trying this again sooner than I may have hoped to. Of course, a mid driver would only work where there was room...pretty much a strat! pete Ok...found it... data sheet with mute NJM2073D amp See page 5, figure 3. Link to comment Share on other sites More sharing options...
psw Posted March 11, 2008 Author Report Share Posted March 11, 2008 In the above post and a few other's I have mentioned "dizzy's" mid driver. Unfortunately, the picture is lost and now it seems the link to the tune has gone too...a russian site. A lot of my old sounds have also gone...oh well, don't use them, you loose them...OR DO YOU!!! Fortunately, I made a copy of this track and posted it on my soundclick page today...I strongly advise listening to this, it is a full production number and ably demos what the sustainer can do. Warmingtone soundclick...select diablo theme enjoy. Further...here is the scant info I have from dizzy himself...I did correspond briefly with him way back when...I am sure he won't mind the MP3 resurfacing... A Member Dizzy_One over at diystompboxes sustainer thread posted something a while ago (jul 21) that may be of interest to sustainer watchers. Basically he has made a Sustainiac copy but with the driver in the mid position and is electronically more complex than my approach but with great and similar results. I've reposted one of his replies to me from there as there's a really nice full production sound clip that's really worth a listen. I can't do the kind of production number he's done and just improvised some single track stuff into the computer, Dizzy's may be a little more accessible and inspiring. QUOTE The driver is a much like Sustainiac bilateral driver. Signal from pickups goes to buffer with a very high impedance, then to a complicated phase and amplitude correction scheme, to a AGC circuit and finally to the power amp (lm386, heh). No a fundamental/harnonic mode because of placement of driver. Just a some mixed mode - harmonics on most bass strings and fund. on high strings. Varying picking style and switching to different pickup combintation, i got a different harmnonics. Sound sample (a theme from some great comp game of the past): Diablo Theme - Dizzy's Sustainer Demo (1.44 Mb). Almost all notes of the lead were picked with left hand only. If you want to know more there was some discussion about it and the link at the top of the page should take you there. There was a Pic too but it's gone now but it looked very similar to the sustainiac single coil pickup on a strat, completely replacing the mid pickup. It didn't work as a pickup as mine does but could be used with either or both pickups. enjoy and thanks to dizzy and the guys over at diystomp... psw I did see a pic and it was a neat bilateral driver in the mid position of a typical strat like guitar. It did not function as a pickup, just a mid driver. As I recall, and it has been a few years, it wasn't overly close to the strings, something that my mid driver required for it to work. The other pickups were SC,s in strat configuration so I am not sure if it would work with an HB in the bridge which would make it just that little bit closer. It is interesting to note that, although secretive about some of the details particularly the phase compensation stuff which he designed himself and at the time I was perhaps overly concerned about, he did confirm that it ran off of an LM386 (a fact I had forgotten) so linear amps are a possibility even in the demanding area of mid-driver operation. I did try my latest design towards the bridge, but while it could move a little in that direction (half an inch perhaps), certainly not enough!!! Anyway...I thought that this might inspire such work, especially with some knowledge that it has been done before, and with the direction that people are generally moving (bi-lateral drivers, etc). I certainly will be giving some thought as to whether to return to building alternatives if the switching is likely to be an "impossible" obstacle. pete Link to comment Share on other sites More sharing options...
Fresh Fizz Posted March 11, 2008 Report Share Posted March 11, 2008 I really hate to say this, but I think the stacked pickup/driver will always be troublesome because of this. One way to deal with it is to sandwich the pickup in between two driver coils which are out of phase with each other. What I understand from Pete is that some extra conditions have to be met: 1. 3 pickup configuration 2. when sustainer switched off the 3 pickups function all passively (no power supply needed) I can remember that we spoke about a sustainiac that used a (step-up ?-)transformer to turn the driver into a pickup. If the transformer is used for that purpose than the schematic of this particular sustainer device could solve this problem. The question is, what transformer is needed, can we buy it, could it be a DIY project? There must be some sustainer schematics with ordinary output stages, no fancy D-amp. How do they switch on/off the sustainer? Nice driver Curtisa, must have a decent self-inductance! Fresh Fizz Link to comment Share on other sites More sharing options...
col Posted March 11, 2008 Report Share Posted March 11, 2008 Great stuff happening at the moment Love the driver Curtisa, I am officially jealous, and will be working on something similar very soon. For interests sake, what wire gauge and number of turns did you use ? ----------------- I have been trying to simulate the Stainiac switching(class-d) amplifier with only limited success so far, it seems like the sort of thing that is on the edge of instability all the time! My understanding is that if it's not set up exactly right, it will be very easy to blow the output mosfets and/or kill the battery in spectacular fashion - is that correct? ----------------- As an alternative, I want to have a go at some sort of class B or AB design that still uses the 'current source' variable output impedance trick - this would let us use much lower resistance drivers, and help to offset some of the dropoff at higher frequencies. Although there will have to be some compromise, because to keep the current linear, the voltage has to rise, and we obviously have a limit on voltage Does anyone have any good simple schematics for a transistor based 1-2Watt power-amp? cheers Col Link to comment Share on other sites More sharing options...
Fresh Fizz Posted March 11, 2008 Report Share Posted March 11, 2008 My understanding is that if it's not set up exactly right, it will be very easy to blow the output mosfets and/or kill the battery in spectacular fashion - is that correct? Yes! Allways open one mosfet switch before closing the other one. I read it somewhere in the patent. As an alternative, I want to have a go at some sort of class B or AB design that still uses the 'current source' variable output impedance trick - this would let us use much lower resistance drivers, and help to offset some of the dropoff at higher frequencies. Although there will have to be some compromise, because to keep the current linear, the voltage has to rise, and we obviously have a limit on voltage I don't think you need lower resistance drivers. The lm386 with the current source trick could still be applied but now with thicker wire and more turns of copperwire. Available headroom is indeed a problem, the current source trick should be combined with the drive current limiter. FF Link to comment Share on other sites More sharing options...
curtisa Posted March 12, 2008 Report Share Posted March 12, 2008 Thanks for the kind words on the driver, everyone. ...any chance of testing it in a mid position? Still searching for appropriate magnets. Couldn't find anything locally. Been looking at the Aussie Magnets website. Having a bit of trouble working out how they determine the magnetic direction of each magnet. I was considering getting a couple of different types for comparison - maybe a pair of ferrite magnets and a pair of Alnico ones. I need one magnet for each coil, and the magnetic direction needs to be North on the biggest flat face of the magnet to South on the opposite side. If the thing could operate with either/and neck and bridge pickups, sophisticated switching as with the sustainiac would seem obsolete and the driver could be designed and remain with this function. As ambitious as this might sound, this is exactly what Dizzy achieved with his bi-lateral driver and circuit and even got unusual effects depending on the pickup combinations (harmonic flavours for instance) and the proof is in the hearing (see the sustainer sounds thread). I suspect that with out a dual use driver as pickup the switching would be considerably easier if not possible passively (no bypassing required) and this was alway the aim of my adventures in mid driver construction... Yep, I was actually intending to remove the 5-way switch in the HSH S470 and go with a 3-way "John Pettrucci" switching scheme - with a mid driver fitted the guitar will be reduced to a HH configuration anyway. I modified my RG7620 from the fancy pants 5-way HH configuration down to the JP 3-way scheme years back, and I much prefer it to the way it was originally fitted out. Ok...found it... data sheet with mute NJM2073D amp See page 5, figure 3. Thanks Pete, I'll have a closer look at it tonight. For interests sake, what wire gauge and number of turns did you use ? 28AWG (0.32mm). Thicker wire than the original 0.25mm specced by Pete, but apparently the same guage as used by Sustainiac in their stealth system. Could only fit on 140 turns on each coil, and have yet to measure the DC resistance, but if it turns out to be a bit low I was thinking I could connect them in anti-phase series (like a regular humbucker) and still get the same effect. If it turns out to be no good with 140 turns I can easily strip it all out and rewind it with more turns of thinner stuff. Those two coils only took me about 15 minutes each to wind and tape. Link to comment Share on other sites More sharing options...
psw Posted March 12, 2008 Author Report Share Posted March 12, 2008 28AWG (0.32mm). Thicker wire than the original 0.25mm specced by Pete, but apparently the same guage as used by Sustainiac in their stealth system. No...I spec 0.2mm for thin coil drivers, 0.25 is used as an example that will work but lack high string response!!! Sustainiac, well that is a different kettle of fish, as is any dual coil design...a good formula has yet to be "published" on that one, bi-lateral or not! I suspect this massively higher wire gauge is well suited to the way in which you describe, and other articles I have read to try and understand, these D-class and current amps appear to work. Still searching for appropriate magnets. Couldn't find anything locally. Been looking at the Aussie Magnets website. Having a bit of trouble working out how they determine the magnetic direction of each magnet. I was considering getting a couple of different types for comparison - maybe a pair of ferrite magnets and a pair of Alnico ones. I need one magnet for each coil, and the magnetic direction needs to be North on the biggest flat face of the magnet to South on the opposite side. Before going there, do try the craft shops and bargain places, you may find just the right thing in ceramics. Even a pair under each magnet. Unfortunately I moved a year ago as funnily enough I lived really close to them. They are actually a little shop and you can walk in a play with a "wall of magnets"...hehehe...magnet heaven. I don't know if there was a minimum order or I had to get a few to make postage work out, you get them cheaper in quantity. I sued them to get the little neodyminium magnets for the HEX models, with 12 per driver, I was going through a lot...still have a few but they are not much good for much else. I actually use them now to trigger the reed switch in my calculator converted into a winding counter thing on the machine that I built to make the ultra-thin coils. with a mid driver fitted the guitar will be reduced to a HH configuration anyway. Now this is going to be very adventurous. Even the sustainiac pretty much specifies that their mid driver thing was for strat type guitars. Putting a mid-driver between the two HB's is going to be really close to both of them, my HEX things came close, but even they wouldn't cut it I suspect and these had effectively 6 opposing drivers and magnetic shielding strategies, along with a novel "coil orientation"...EMI is goint to be tough. Also, my rail style mid-driver with the HB in my strat came close to working, but having to be so close to the strings was horrific for playing, exactly where you don't want something a mm or so under the strings... The magnets used in these were craft shop magnets and just the right size to fit half the string set. Others would also be ideal, I would suggest perhaps two 10mm discs under each core for instance. Fortunately you will have the chance to try any number of magnet types. One of the neat things about the bi-lateral design over the HB or rail is that I suspect, like my single coil drivers, they may have a bit more "throw" meaning they can be moved back a little from the strings and not react so sensitively to action effects. Moving the driver more towards the bridge may also help with these effects too. But as I say, it is going to be asking a lot to get it in between two HB's. Thanks for the kind words on the driver, everyone. Credit where credit is due, it looks like a bought one! I can see the wire is very "thick"...is it "potted"...I am sure that tape tied tight will hold it though. It's certainly made me eye off a few pickups around here. I wanted to put one on a tele I am working on, I was thinking of making a custom thin driver and sticking it up against the neck, but perhaps I should experiment with a dual or more core device and see if I can get it to work in the middle on such a guitar. If I could make one thin enough, perhaps I could surface mount it without digging into the guitar! Making something neatly is a very good sign, it doesn't have to be this "pretty" but you can see the build quality that will on aid in the end with those little bits of extra performance that may be required and give the thing every chance of proving itself. If your mid driver scheme is successful, It may well prove the solution to the switching problems...just turn the thing on...hehehe...be prepared for a struggle though, I don't know that it will go easy into this position. good luck...pete Link to comment Share on other sites More sharing options...
col Posted March 12, 2008 Report Share Posted March 12, 2008 (edited) 28AWG (0.32mm). Thicker wire than the original 0.25mm specced by Pete, but apparently the same guage as used by Sustainiac in their stealth system. Could only fit on 140 turns on each coil, and have yet to measure the DC resistance, but if it turns out to be a bit low I was thinking I could connect them in anti-phase series (like a regular humbucker) and still get the same effect. If it turns out to be no good with 140 turns I can easily strip it all out and rewind it with more turns of thinner stuff. Those two coils only took me about 15 minutes each to wind and tape. According to the calculator, they should be around 2ohm (I guessed at a core length of 25mm and width of 5mm). As far as going series instead of parallel: The impedance presented to the amp at higher frequencies will be much higher with the series configuration. In series, the inductances add up, in parallel, it's the same reciprocals rule as for parallel resistors. It's not as simple in our case because of magnetic coupling between the fields, but I guess that there will still be a big difference. According to the simple rule, assuming 2ohm 1mH coils in series, you have impedance of 8.5 ohm at 600Hz in parallel, you would have 2.3 ohm at 600 Hz With field coupling, the parallel result might be more like 3 or more ohm ? Still a big difference though. The series driver will need more voltage to get the same current through those coils at higher frequencies! Only half as much current gets to each coil in the parallel config compared with the series one. But there is 3 or 4 times the impedance in the series driver at a given frequency. So, even supplying twice the current to the parallel driver to provide an equal current per coil you will need less power to drive 'X'mA per coil through the parallel driver. Col Edited March 12, 2008 by col Link to comment Share on other sites More sharing options...
psw Posted March 12, 2008 Author Report Share Posted March 12, 2008 As far as going series instead of parallel: The impedance presented to the amp at higher frequencies will be much higher with the series configuration. Thats interesting col...so there is quite a bit of difference for some designs being series vs parallel besides the number of turns required to make a resistive load and with more impedance this would seem to imply more potential phase changes with frequency. That is a shame because if we are to take you theory that my coils may well be largely working in the resistance range and so not so bothered by the effects of changing impedance with frequency, then I should consider parallel. Intuitively (of course I don't have anything to base this on), I would have thought it would be the other way around, to get the same resistance in parallel you need multiple large coils with lots of turns, the mid driver of mine for instance requiring 2x16 ohm coils to make 8 ohms. (I suppose I imagine the power running around and around the turns, the more there are, the "slower" the driver, the more impedance to it's travel...metaphorically speaking In series I imagine it needs to run oune coil, then the next, but these coil lengths, turns are less...but this is obviously just "made up" assumptions based on a large degree of ignorance in such matters). It is interesting because, thinking about the mid-driver quest that curtisa is going on, I drew up an idea I had thought in relation to the HEX designs and the type of ideas that may be required to get a mid-driver working, especially with two HB's. These are simplified Hex (hex=6) ideas that I never really made in this form BTW... What I was thinking was making a HEX version of my present single coil. 6 very thin coils with alternating north and south polarities and reverse windings. If I could get clever with a jig with 6 coil spaces, I could perhaps make them so each alternate flip and so effectively reversed and connected in series...however, perhaps I need to reconsider this in light of what col has posted. As I may have mentioned before, a bi-lateral driver has poles that attract across the strings so a large part of the EMI is directed in that direction. The HEX idea is of course to create this effect in an even more localized area. Well, at least that is the intention, hopefully resulting in less EMI making it towards the pickups. With the 2xHB set up, you are really going to be up against it because regardless of the localizing effects of the bi-lateral or even more elaborate designs like this, it is likely that flux will be traveling down the strings. On way of dealing with this is to reduce power. If the driver is sufficiently efficient (as for instance my ultra thin drivers appear to be) they can run on less power and so emit less EMI for the same effect. People using high powered amps take note. Another strategy is to raise the device and the pickups very close to the strings, and reduce power...this is what I had to do with my rail design. I gave it up for my recent designs as I just found that the mid-driver was physically in the way of picking the guitar! Additionally of course, not every guitar has a mid-pickup slot to accommodate it and it was a bugger to make! It's performance (at least with mine) no where near met that of the original thin driver. ------------- I might hold off on these ideas as it may well be that the mid-driver is a more difficult nut to crack than the switching problems! I hope everyone has listened to Dizzy's mid-driver diablo theme, it really is very good both in production values, musical potentials of controlled feedback, clean and dirty sounds and the mid-driver concept as well...I had a copy on my MP3 player for a long while! -------------- On the topic of switching...I have tried to work out discrete modules for switching. This is how I economically and effectively create a bypass with a spdt switch (possibly part of a larger switch array of course like a 4pdt which offeres 4 such spst switches) and a very basic 5tdp strat switch...the individual tone controls now wired to a master frees up one side of these standard lever switches... This switches the selector to bridge only with a single switch, in the up position bridge is only connected for sustain mode, down returns to what ever the selector switch is set to. It avoids problems of position 4 where the bridge and middle would have been connected within the common selector switch. It does however leave the middle and neck connected to ground, so does not completely bypass it, and it of course switches instantaneously, so if a delay were required before bring back the neck and middle pickups, this is where it would be required I guess...a delay after switching off the power I mean, to avoid the off "thwack"! Shame, because it works really well...make a good schematic for a simple "solo" switch if that were desired. A 4053 is supposed to have problems with switching noise I have heard, however, a 4066 quad normally open 4xspst electronic switch does not suffer so. I wonder if any of you clever fellows, perhaps some of the lurkers (we have had well over a thousand visits in the last week or so!) may have some ideas for such a switch...or indeed FET's. You would want a delay to this switch on switch off, so that the bridge stays on a little longer after the power is cut. On switch on, you would want it to switch instantly or possibly slightly ahead of power being switched on...that is the bridge pickup (and most importantly the neck and middle) would be disconnected before the power was applied. This latter requirement is less of a problem and instantaneous switching my be ok on switch on. A clue is probably available in the mid pickup/driver "gate filter" in the sustainiac patent that uses a diode and capacitor to change the delay. A 4066 would open with power cut, but a cap would allow enough stored energy to keep it closed a little longer if that is any help. Hopefully such a scheme would include the possibility of passive operation in off mode. While electronic switching takes up very little power, it means the guitar would not work without the power and would ideally be avoided. However, if you took this switching model as it's basis, the guitar would work with the bridge HB alone if so selected, only the neck and middle requiring power to operate in a more elaborate electronic switching scheme. This may be important if it is detirmined that the common ground of the middle and neck pickups required disconnecting or shorting, loading or paralleling with the driver. This may also be important if I were to move to a BTL amplifier design which must not have a common ground attached, that and 4 times the power of course being an attraction to such a circuit (not that I have had a lot of luck with them in the past!). Ok...some things to think about...not sure of any answers. I will be very interested in seeing curtisa's progress with the whole mid-driver thing. How are others plans into bi-lateral or other designs going? pete Link to comment Share on other sites More sharing options...
col Posted March 12, 2008 Report Share Posted March 12, 2008 As far as going series instead of parallel: The impedance presented to the amp at higher frequencies will be much higher with the series configuration. Thats interesting col...so there is quite a bit of difference for some designs being series vs parallel besides the number of turns required to make a resistive load and with more impedance this would seem to imply more potential phase changes with frequency. That is a shame because if we are to take you theory that my coils may well be largely working in the resistance range and so not so bothered by the effects of changing impedance with frequency, then I should consider parallel. Intuitively (of course I don't have anything to base this on), I would have thought it would be the other way around, to get the same resistance in parallel you need multiple large coils with lots of turns, the mid driver of mine for instance requiring 2x16 ohm coils to make 8 ohms. (I suppose I imagine the power running around and around the turns, the more there are, the "slower" the driver, the more impedance to it's travel...metaphorically speaking In series I imagine it needs to run oune coil, then the next, but these coil lengths, turns are less...but this is obviously just "made up" assumptions based on a large degree of ignorance in such matters). Do you remember a while back when I proposed a dual coil wired in parallel, I suggested that based on 0.2mm wire working well for a single coil, that 0.15 wire would be good for a parallel dual coil? If you want to keep the driver working in the resistive range (no messing with current source amps etc), then you want to avoid having to have huge(many more turns) coils in order to achieve your 16 resistive ohms without a much bigger inductance - for this you could use fewer turns of thinner wire. Personally, I'm more interested in this 'current source' idea - in either case, a parallel driver to maximize the efficiency. I have thought about ideas like having 4 or 6 coils in a line, but I imagine that we would start losing efficiency due to higher levels of coupling between the individual coils (the more coils you add, the smaller they have to be, and the more coupling there will be between them and their neighbors due to proximity - so its a case of diminishing returns, two coils may be the optimum compromise when issues such as build complexity, field shape and magnetic coupling are considered, although a four section driver is tempting because it may be possible to get circular bobbins and magnets more easily than half length pickup style ones. As I may have mentioned before, a bi-lateral driver has poles that attract across the strings so a large part of the EMI is directed in that direction. The HEX idea is of course to create this effect in an even more localized area. Well, at least that is the intention, hopefully resulting in less EMI making it towards the pickups. Not so sure about that. It may be that the benefit of the bilateral approach is that it keeps the magnetic circuit at 90º to that of the pickup - adding more sections to it doesn't change that. Moreover, if more smaller sections reduces EMI by making the field smaller, then it won't work as well as a driver, so no improvement there either. With the 2xHB set up, you are really going to be up against it because regardless of the localizing effects of the bi-lateral or even more elaborate designs like this, it is likely that flux will be traveling down the strings. On way of dealing with this is to reduce power. If the driver is sufficiently efficient (as for instance my ultra thin drivers appear to be) they can run on less power and so emit less EMI for the same effect. A more efficient system allows you to get the same magnetic energy to the strings with less battery power. Any fizz caused by the strings transmitting flux from driver to pickup isn't going to be fixed by improving the efficiency of the system. It is the flux that is driving the string - remove the flux and you remove the drive. It is possible that focusing the field should help and a humbucker configuration will do this, but at the end of the day, you need flux at the strings, and this will be transmitted to the pickup. Reduce the flux and you reduce the drive. If you reduce the power and compensate by moving the driver closer to the strings, you still have the same amount of flux getting to the strings. ------------------------------------------------------------------- I have some old pickup bobbins and a few old transformers with laminated cores ready to go... still no luck simulating a class-d amp - but I'm learning a lot, and also no magnets suitable for the bi-lateral driver yet. cheers Col Link to comment Share on other sites More sharing options...
psw Posted March 13, 2008 Author Report Share Posted March 13, 2008 Do you remember a while back when I proposed a dual coil wired in parallel, I suggested that based on 0.2mm wire working well for a single coil, that 0.15 wire would be good for a parallel dual coil? Yes...I may have abandoned the rail driver too soon (remember when that was the go just as the bi-lateral is today)...people with an interest in patents and alternative designs may wish to look at these fernandes concepts including various rail and side wound designs...5,585,588 tumura / fernandes patent At the time I was hoping that using components at hand and approachable building techniques, I could produce something that I expected to refine more. This idea of less turns and thinner wire would have been the next step I suspect and perhaps I should have gone in that direction. I know I do not use scientific methods and fail in many skills and knowledge...that is why this thread exisits, to gain that whet I lack from others...for any input, I welcome it. However, some of what I suggest is based on actual experience and observation not from theory. At times these appear to conflict. I resort perhaps at time to naive or faulty ideas of why these things occur and these may well and probably are wrong or at least insufficient metaphors...there is a lot to take in and I have failed (not for lack of trying mind you) to digest all there is to consider and to understand it with what I have observed. I imagine that we would start losing efficiency due to higher levels of coupling between the individual coils (the more coils you add, the smaller they have to be, and the more coupling there will be between them and their neighbors due to proximity - so its a case of diminishing returns I don't quite understand this for instance. The magnetic coupling is a bad thing? Even though the poles are reversed with respect to their neighbors, so to are the coils. I could see that perhaps eddy currents between these opposing coils might have a detrimental effect for instance. The coupling would be a deterrent to sending different signals into different coils as the whole structure is magnetically coupled. Different sized coils to apply more drive to the higher strings may result in a lessening of the EMI dampening effect of such a design too. issues such as build complexity Well, everything has it's complexities, the making of bobbins for instance seems to be more of a detriment to most than the design of a circuit! In conceiving such designs, the ability to make them are to the forefront of my mind. For instance, such a coil could be constructed with my winder and a bobbin with 6 spaces that come apart. Epoxy would create separate coil discs with hollow centres. A drinking straw could be used (the inspiration as one was sitting in front of me last night) through which a bolt could pass, holding all the segments together. If wound in series, as each successive coil is wound, the wire could be taken over to the next from opposing sides...the result would be a string of connected coils wired together and when concertinaed out, would create an alternating reversing of the windings...just like a string of paper dolls. With such a construction it would not be too onerous to make...a parallel version though would be considerably harder, requiring manual wiring of each individual coil. While the size of these coils would need to be small, each coil in series would only need to be 1.33 ohms to make a total of 8 ohms. In it's favour, it would utilize space between poles that in my present designs are occupied by air. The intention is that you would get the response and design considerations/specifications that have shown to work with a single coil (thin design, 0.2mm wire, etc) with the benefits of the multi coil and the bi-lateral ideas. But, perhaps there are things I have yet to consider in such a plan. It also diverts strongly from my ideas of combining passive pickups, magnets and mountings reverting to essentially a stand alone driver. This driver could be made exceptionally thin however and may possibly even surface mount. It is a design in which small neodyminium magnets may have their uses. My illustration showed magnets beneath poles, but the poles themselves could be small neodyminium magnets, powerful but with a very concentrated self attracting (ie attracted to their close opposite pole under the coil as much as to its neighbour) field shape. The entire driver with such a scheme may only be a few mm thick. That is not to say that it would work! There is some attraction to winding cylindrical coils, in lots of ways they are easier, especially in regards to tension and compactness. Perhaps though, I should consult the "calculator" to see if it has a hope of fitting into the required shape and how deep the coils would need to be before I begin such an enterprise. Personally, I'm more interested in this 'current source' idea - in either case, a parallel driver to maximize the efficiency. A very worthwhile pursuit. Obvious with my limitations in this area, it is very difficult to even contemplate taking a lead in such an area. Similarly, I was eying off LCR meters, but I am not sure that I would no what it was that I was reading to interpret it properly. It would be interesting to understand some of the differences in coil types and such in a graphical and real world way...I'd love to prove the theory correct that my coils are largely of a resistive nature and in so doing did find a way of working around the phase issues. Equally, the d-class idea, if only for the savings in power due to efficiency is a very worthwhile pursuit with something that ideally is battery powered. None of any of this I suspect will solve the switching problems. My simple single coil on top of the neck pickup has amazingly good performance...it really does...and is comparable to the sustainer in very many ways (the owner of the guitar I tried side by side with mine had the impression that it could have been better). Obviously, sustainiac has had to dedicate a lot to making their system for all the current source amplification, bi-lateral driver driver as pickup, no secondary coil effects as in my design and other sophisticated design features...to overcome this obstacle. It is entirely likely that I or anyone else attempts such an endeavour (multi-pickup guitar installation) will need to address this in similar ways. It is a challenge that will be there regardless and as such one that I feel a need to try and overcome...but that's just me I guess. One work around of course is the mid-driver which also has the benefits and feature of running it with either or both pickups in drive mode. It is a workaround as if such a device were successful , one could assume, like with a single pickup guitar, all that needs be done is the device be turned on. It was this attraction above all other's that drew me to it enough to make my own rail driver even though dual coil drivers were not something I had actively pursued since the piggyback idea worked so well on the sustain-o-caster. Similarly, it wasn't not the ability to put the coil on top of a pickup that lead me to the thin driver design, that design evolved from it's apparent efficient performance and lower EMI dispersion. That the efficiency may be because of it's resistive nature is plausable (less phase issues, "fast" driver qualities), so too is the idea that it's small size is in some part due to this small profile, an idea that came from making hex drivers only 10mm wide and 5mm deep. I may well be wrong, but something is working...my intention is to make something workable and improve it regardless of why it does what it does, much as that interests me...and leave the improvement of it to the future and a deeper understanding of it. Trial and error is not the best way, but for me it appears that it is all I have at my disposal. Some very knowledgeable people have come and gone on this thread and in others without solving it, perhaps answers are hard, perhaps it is a matter of motivation, perhaps there is no answer with my configuration and criteria. Perhaps I have come to the limits (for now) of what I can do and I must wait till the problem confronts someone else before a solution is found... pete Link to comment Share on other sites More sharing options...
psw Posted March 13, 2008 Author Report Share Posted March 13, 2008 OK...in light of your above post col... A series of 6x 1.33 ohm coils would behave differently than a single 7.98/8 ohm coil? Two reasons for labouring this...one is the option of redesigning my single coils into 6 individual small direction coils around each pole utilizing the space between the poles...the other is to make a multi-coil driver with different poles and reverse coils. This design, with the same wire specs, magnet strength, etc, would be expected to behave differently are you saying? A parallel driver would be more efficient because it would have more turns, but these turns could be reduced with a reduction of wire size...is this the gist of it? I can see how it "could" be done, and it need not be that labor intensive, but it would have to have benefits of some kind to even attempt it. I will be watching other bilateral designs with interest for this very reason. Another reason I have an interest in this is that I am going to get around to a piggyback HB style driver in the near future as a complement to my present design. I have a few ideas, however the one I had been favouring to start with was a pair of 4 ohm coils in series. Two variations come to mind that I have brought up before...two full width coils and two half width coils...kind of a piggyback bilateral design in a way. Of course, you may suggest a thinner wire, less turns and a parallel wiring...what would the advantages and side-effects be of such a scheme? I had always thought that a fair wire gauge was required, in my case 0.2mm, in order to carry the current within a driver coil. The balance being between more current capacity with thicker wire (as with curtisa's recent coil) but more turns and size to create the load against thinner wire having less turns but less current capacity in the wire. I had the impression for instance, which may be completely erroneous, that a pickup coil would not work as a driver regardless of the massive load, because the wire would not be able to carry sufficient current. It was a large part of what surprised me about spazzy's PA driven pickup driver, that perhaps he could overcome impedance mismatching with sufficient power, but that it may well self destruct (like fuse wire) or simply not allow that kind of effect to occur. Obviously somewhat skeptical, however it has always been suggested that the father of the sustainer, Micheal Brook and his infinite guitar, used a conventional pickup as a driver and a large impedance matching transformer to make it work...hmmm While my pickup in parallel with the driver coil presents a similar load (7.5ish) and is obviously carrying a lot of voltage (curtisa measured his as having perhaps 100vac) the current must be very low as, well I am not dead yet, and there is no sign of heat or problems with any pickups the device has been sitting on, at least one now for over three years! Anyway...perhaps I am only considering alternate drivers to take my mind off of my switching woes for now, I wonder if I had a plan there that I would be considering hex designs again if what I had already was fully integrated pete Link to comment Share on other sites More sharing options...
curtisa Posted March 13, 2008 Report Share Posted March 13, 2008 I can see the wire is very "thick"...is it "potted"...I am sure that tape tied tight will hold it though. The coils have been potted in PVA. I was using a small paint brush to apply a layer of glue to the coil every 20 turns or so. The photo you have there is the last one I took before I applied the final coat of PVA and selaed it up using self-amalgamating silicone tape. If you look closely at the photo you can see the white of the previous layer of PVA just showing through between the copper wire. With the combination of thicker wire and shorter winding length, the whole coil feels more "solid" anyway, so I'm expecting the driver to be less prone to vibration and microphony. The windings on the full-length bobbin on my previous driver felt very loose as it was difficult to get the copper wire tight on the longest run of the bobbin (from bass to treble). The series driver will need more voltage to get the same current through those coils at higher frequencies! Only half as much current gets to each coil in the parallel config compared with the series one. But there is 3 or 4 times the impedance in the series driver at a given frequency. So, even supplying twice the current to the parallel driver to provide an equal current per coil you will need less power to drive 'X'mA per coil through the parallel driver. True, but with the class-D amp, I'm already running at full voltage (switching hard positive to hard negative), so the pulsewidth of the switching action will then define the amplitude of the average driver current. Time and trials will tell, but I reckon the class D chip will be quite happy driving a 2x2 ohm series inductive load. I have two TPA2000D1 2W class D chips on their way to me for trialling in the next week or so, so I'll be able to have a play with the new system soon. The chip is still an SMD device, but it has a slightly wider pin spacing than most others I've been able to find, so it should be just easy enough to manually solder. Failing that I can get the dual MOSFET driver chip used in the sustainiac patent for around 50 cents a pop, and try building the amp that they use in the patent. @Pete: I had a look at the datasheet for the NJM2073 you suggested. The mute scheme they show seems a bit crude, forcing the output stages into cutoff - could be prone to pops when engaged? I found a possibly better solution in the TDA7052B, a 1W BTL chip with DC volume control in an 8-pin DIL package. The DC volume port is handy because you can implement the mute function, AGC (if necessary) and drive level all in the one pin. Could be quite handy if you're looking to save space while maximising flexibility and expandability of the system. Link to comment Share on other sites More sharing options...
psw Posted March 13, 2008 Author Report Share Posted March 13, 2008 @Pete: I had a look at the datasheet for the NJM2073 you suggested. The mute scheme they show seems a bit crude, forcing the output stages into cutoff - could be prone to pops when engaged? I found a possibly better solution in the TDA7052B, a 1W BTL chip with DC volume control in an 8-pin DIL package. The DC volume port is handy because you can implement the mute function, AGC (if necessary) and drive level all in the one pin. Could be quite handy if you're looking to save space while maximising flexibility and expandability of the system. That's weird...This was actually my first choice a year or more ago and I actually bought one in a kit would you believe. I didn't realize that pin 4 was a volume control...there was no mention of it, I dug up the instructions and it is just labeled NC (not connected) with no clue to it. It didn't seem to work as I'd hoped, I went through a stage of building numerous different mini-modules at one point. I don't recall who was around then, but I was reminded of it the other day looking for the mid driver pics... I am not sure where it is now, but I am sure that I would have used an IC socket, so this could be interesting. I lost faith in the whole BTL thing after some lack luster experiences. I was particularly pleased with the one on the right, this is a BTL dual LM386...notice in this mode no output caps. I guess I was wondering if the output caps may be a source of "pops" and the whole sharing ground issues, both of which seem to be avoided with BTL configurations. Very cute though! The circuit I use is also very small and seems to work pretty well in a linear way, plus it has got some basic AGC...the best I have come up with and I have made a few and none have failed yet which is a good sign! With so many visits, I guess there will be people looking in who are wondering what each of us are working on, the above is the size of my present circuit, the left an example of the driver coil on top of a conventional SC pickup. I am sure that there will be better strategies, amps and such to pursue...I did do some work with some SMD stuff...I still have a bunch of SMD lm386's but boy are they hard to solder...there are ways, but I don't make circuit boards, so that makes it harder. One way I heard is to superglue the thing down careffully (tweezers and a magnifying glass, an SMD LM386 is less than 3mm long!!!) then solder everything, then use a solder wick to remove the solder...enough will be left to make all the connections, so they say! I actually did use a few tantalum and chip capacitors to reduce size, and these are SMD's...I solder a loop of component tail around them, then I insert this wire onto the board and solder, then cut the loop above...works a treat! SO, given that it works and no one has placed much store in the idea that fizz or pop is being transfered through the circuit's common ground, I doubt it will "fix" my particular problems and am therefore a little loath to replace this circuit. If you change too many things at once, especially with my trial and error methods, it is hard to tell what is working and what is letting you down. To be successful I have found it best to trial one thing at a time. Switching I suspect will only be solved through delayed sequential switching...I don't think it need be quite as elaborate as the sustainiac's, but who knows...I may be a little out of my depth. The other strategy is avoid the whole issue with a single pickup guitar (in which mine works perfectly with no switch noise and great sustain...although no harmonic switch) or the more challenging mid driver where again, bypassing is not necessary. Bypassing is not a problems as my drawing shows, this works fine and is noise free without a battery connected for instance...someone will have to get clever with it! I am still not clear as to where the noise is emanating from, if it works well and silently with the other pickups not connected, then there is something in that connection which results in the pop, not the circuit per se. Interestingly, it pops even if in position 5 where the bridge pickup is selected anyway...the only place it could be getting in then is the shared ground of these other pickups or the driver as the pop isn't there if these are permanently severed. The coils have been potted in PVA. Ahh...the old PVA, still a very good option in my book...safe and reversible!!! Time and trials will tell, but I reckon the class D chip will be quite happy driving a 2x2 ohm series inductive load. I think so too, at least worth a go...to me it sounds like a "current source amplifier" is quite a bit different in many ways. I am surprised that sustainiac were able to do it in the manner that they have (not a dedicated chip) as I thought such arrangements were very temperamental. I am still not sure if the sustainiac is using quite what the patent describes either...I was tempted to buy one myself, even a fernandes is itself reasonable on ebay...but you know, dedicated to the DIY thing, god knows why I could have easily bought a dozen of them by now... Oh...as a side thing, has anyone got any cool ideas for pickups. I have a roll of pickup wire and half a winder I could fix up and with all these bobbins and stuff about, I probably should give something like this a go. Unfortunately, most of the ideas I have would demand custom bobbins. For all the artsycrafty things I have done this is something that I have never had much luck with, bobbin making better run... pete Link to comment Share on other sites More sharing options...
col Posted March 13, 2008 Report Share Posted March 13, 2008 OK...in light of your above post col... A series of 6x 1.33 ohm coils would behave differently than a single 7.98/8 ohm coil? When I was talking about the differences I was really thinking more specifically about parallel connected coils, however, for series coils, there will also be some differences. The flux linkage will not be the same with 6 separate coils, so there will be a difference in the inductance of the driver. There are likely to be difference in the shape and 'throw' of the induced magnetic field. A parallel driver would be more efficient because it would have more turns, but these turns could be reduced with a reduction of wire size...is this the gist of it? ... Of course, you may suggest a thinner wire, less turns and a parallel wiring...what would the advantages and side-effects be of such a scheme? The suggestion of using thinner wire in two parallel coils was if you want to use parallel coils while still keeping the driver working predominantly in the resistive range over the desired frequency band, I'm not sure if there's much to be gained. I had always thought that a fair wire gauge was required, in my case 0.2mm, in order to carry the current within a driver coil. The balance being between more current capacity with thicker wire (as with curtisa's recent coil) but more turns and size to create the load against thinner wire having less turns but less current capacity in the wire. I had the impression for instance, which may be completely erroneous, that a pickup coil would not work as a driver regardless of the massive load, because the wire would not be able to carry sufficient current. A pickup coil wont work in a system like ours because the resistance is so high that most of the energy is dissipated as heat - its very inefficient. Maybe with a mains powered amp it can work well even with those efficiencies... ============================================================================= The series driver will need more voltage to get the same current through those coils at higher frequencies! Only half as much current gets to each coil in the parallel config compared with the series one. But there is 3 or 4 times the impedance in the series driver at a given frequency. So, even supplying twice the current to the parallel driver to provide an equal current per coil you will need less power to drive 'X'mA per coil through the parallel driver. True, but with the class-D amp, I'm already running at full voltage (switching hard positive to hard negative), so the pulsewidth of the switching action will then define the amplitude of the average driver current. Time and trials will tell, but I reckon the class D chip will be quite happy driving a 2x2 ohm series inductive load. So you are running at full voltage - but with a series wired coil, your total impedance will be higher, so the current in each coil will be lower when compared to a parallel wired driver == poorer efficiency/drive. You also still have the problem of drop off at higher frequencies with a higher inductance driver... it seems that what the sustainiac circuit is doing with their current feedback system is keeping the 'average driver current' steady by altering the pulsewidth depending on their feedback signal. I suppose that the limiter is required to prevent the pulsewidth getting too asymetrical and causing shoot-through on the MOSFETS ? About the Sustainiac circuit: A few concerns I have are related to the fairly low frequency of their carrier signal and the lack of an output filter - will this not cause some 'false' balancing of the current due to the very high impedances at the switching frequency ? Maybe it is important that the inductance of the driver is greater than some set value to ensure that the system does not react to the carrier frequency ? I have two TPA2000D1 2W class D chips on their way to me for trialling in the next week or so, so I'll be able to have a play with the new system soon. The chip is still an SMD device, but it has a slightly wider pin spacing than most others I've been able to find, so it should be just easy enough to manually solder. Failing that I can get the dual MOSFET driver chip used in the sustainiac patent for around 50 cents a pop, and try building the amp that they use in the patent. I'm looking forward to reading about how you get on @Pete and Curtisa, I posted about the TDA7052 gain control ages ago (Dec 2006). There are two versions, one has the voltage controlled gain, one doesn't, unfortunately the more readily available one(here at least) is the one without gain control. I think it's the TDA7052A that has the control pin. cheers Col Link to comment Share on other sites More sharing options...
zeppelinchld Posted March 14, 2008 Report Share Posted March 14, 2008 im just wondering, is there an official schematic telling what goes to input and where the harmonic switch would go or could someone just tell me? Link to comment Share on other sites More sharing options...
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