psw Posted March 7, 2008 Author Report Share Posted March 7, 2008 Yes, well I was going to perhaps suggest this too. So, if you were to get one of these bobbins and cut it neatly between the D and g strings and then remove a bit between the cut end and the d and g string poles, you would have two half bobbins that could be glued back together. Personally, I would also use the thin driver principles too and so block up the lower portion a bit depending on the amount of coil you propose. Perhaps not with two 16 ohms for instance making an 8 ohm coil in parallel...you could go real thin and do two 4 ohms in series...or have I got that around the wrong way...hehehhe So, along with these you could get a set of steel slugs or use bolts for the poles and then attach two half magnets to the bottom, or a couple of round ones. I have found some usable things in craft sections of $2 shops or riot art supplies and stuff, I guess people make fridge magnets or something from them...very cheap ceramic things, but work fine. Otherwise, for more specialised things I have used AussieMagnets, but they don't sell legit pickup magnets or sizes, good for rare earth and stuff. Problem with StewMac is a minimum order and freight. I know allparts have some and a few others are getting into pickup parts and I think there is an australian distributor so perhaps a store could order in a couple. Otherwise, if you poke about, you often find that cheap single coils are made on a bobbin with the magnets inserted or steel slugs with a ceramic magnet under. Rarely are these made in the traditional fender way with plates and wound directly onto the magnets (which are not really as suitable)...even if the poles are actually alnico. So, if you find a cheap pickup about, this would work too. You may even find that some cheap SC pickups have a slot for the steel slugs as I did with the sustain-o-caster pickup that enabled me to put a blade in place of the poles that had been there. Poles seem to work fine though, so I wouldn't fret overly about it. here is a recent thread on this very topic for instance... Where do you buy pickup magnets "You can also try GuitarJones, but he is nearly inpossible to get stuff from if you do not place large orders, GuitarPartsUSA have some pickup parts and Allparts have a lot, even if they do no list them in the catalog." Allparts pickup parts page However if you consider their prices, $5 for a set plus the slugs and maybe the mounting, plus you need to find suitable magnets...you would have to be tempted to find some dirt cheap Hb or other pickup and just strip the wire out of it...after all, you don't even care if it works or what it sounds like! I once told a repair guy in a shop what I was trying to do and he gave me a couple of cheapo pickups...a lot of pickups get replaced and stuff and need a good home. Certainly I think that for this design, this strategy is going to be easiest and look the best with a very good likelyhood of a good working model and none of the super hassle of making a bobbin yourself. With an HB, you could get too shots at it or compare a series to a parallel type coil. I think there should be plenty of room if not wound as thin as mine for the coils to wind next to each other between the g and d strings, after all, sustainiac can do it so it can be done. I suspect that a nicely wound coil should superglue back together nicely for instance and as I say, if you used an SC, the cover would hide the join and hold it all together very well. Hope all that helps and we see some of these things real soon...so nice to have someone else do this to save me the effort. I do appreciate the design and the intention. I will in fact be making a stand alone pickup for my telecaster to sit next to the neck pickup so I am not against this idea at all. I just have my own path to follow at the moment with a broader range of criteria. When I get to making my own HB sized driver/pickups I may well use previously posted ideas of bilateral piggyback coils, half on one bobbin and half on the other for instance...or I may make full coils. I am dealing with the SC size and magnetic limitations for now, but this will not be the end of the story...it is easier though, half the coils for a start...and very effective, surprisingly so for it's simplicity. I was just checking out the plan I had for -ve switching the thing and I don't think it will work...so now I am back to a 3pdt switch again...grrrr I had the -ve connected to the ground end of the driver, the driver connected to the pickup so when the neck pickup is connected to the driver, the power would also be supplied via the common ground to the circuit turning it on. It would appear though that power may also get through the driver and pickup coils into the ground and so the circuit even when bypassed, so that is not likely to work, rats. Still, it is a little more progress than before. Any ideas on the ramifications of using it with a power supply with a battery installed and connected also. Battery drain anyway, damage, explosion???!!! Perhaps I could find a power socket that would switch out the battery if connected. I am leaning towards a conventional power socket kind of thing in addition to a standard phone plug rather than a special din or something, but I don't like the idea of having to remove the battery or install a special switch to change from remote power to battery. hope all that helps and gives people ideas...now go build a bi-lateral driver, prove the theory. Then you might be tempted to go all the way and make six opposing little coils and you will have made the HEX concept work tooo!!! I was doing something like this for a 4 string bass a while back with 8 drivers, two per string...but I have shelved that for the moment as i do not think that the world disparately needs a bass sustainer!! pete Link to comment Share on other sites More sharing options...
curtisa Posted March 7, 2008 Report Share Posted March 7, 2008 Yes, well I was going to perhaps suggest this too. So, if you were to get one of these bobbins and cut it neatly between the D and g strings and then remove a bit between the cut end and the d and g string poles, you would have two half bobbins that could be glued back together. Personally, I would also use the thin driver principles too and so block up the lower portion a bit depending on the amount of coil you propose. Perhaps not with two 16 ohms for instance making an 8 ohm coil in parallel...you could go real thin and do two 4 ohms in series...or have I got that around the wrong way...hehehhe At this stage I'm curious to see what makes the "thick" driver so usable with sustainiac's systems, so I'll pursue that first before trying to thin it down further. The info I have suggests that 256 turns of 32AWG wire is used on each coil, and the measurements shown in that pictorial indicates around 4-6 ohms DC resistance per coil. Coupled with the patent info it appears that both coils are connected in parallel with the windings in phase with each other, giving a potential total resistance of <3ohms (!!). I assume that if the windings are the same direction, the magnets need to be in opposite polarity for the scheme to work properly. However... The switching class D amp they use keeps the frequency constant at roughly 30KHz, and reproduces audio frequency variations by PWM-ing the output signal. The inductive impedance at 30KHz is also going to be a lot higher than 3 ohms. I wonder if the very nature of a class-D amp makes it better suited to evening out frequency response variations and problems in our DIY versions because the applied frequency is constant and unwavering? So, along with these you could get a set of steel slugs or use bolts for the poles and then attach two half magnets to the bottom, or a couple of round ones. I have found some usable things in craft sections of $2 shops or riot art supplies and stuff, I guess people make fridge magnets or something from them...very cheap ceramic things, but work fine. Otherwise, for more specialised things I have used AussieMagnets, but they don't sell legit pickup magnets or sizes, good for rare earth and stuff. Good suggestions, I'll try a few of those. Problem with StewMac is a minimum order and freight. I know allparts have some and a few others are getting into pickup parts and I think there is an australian distributor so perhaps a store could order in a couple. Otherwise, if you poke about, you often find that cheap single coils are made on a bobbin with the magnets inserted or steel slugs with a ceramic magnet under. Rarely are these made in the traditional fender way with plates and wound directly onto the magnets (which are not really as suitable)...even if the poles are actually alnico. So, if you find a cheap pickup about, this would work too. You may even find that some cheap SC pickups have a slot for the steel slugs as I did with the sustain-o-caster pickup that enabled me to put a blade in place of the poles that had been there. Poles seem to work fine though, so I wouldn't fret overly about it. Stewmac was only as an example, I'm sure there are many others. And like you say I can probably find some shitty single coils I can destroy from somewhere. Regarding the opening in the bobbin for the pole pieces, it'd be better if the bobbin had six individual holes rather than one continuous slot - when I make the cut I need to have something to keep the two half-bobbins from collapsing once it is split. Any ideas on the ramifications of using it with a power supply with a battery installed and connected also. Battery drain anyway, damage, explosion???!!! You need a way to keep the powerpack voltage from "charging" the battery when applied. Regular batteries, as I'm sure you're aware, do not like being recharged. Perhaps when you have the extrnal supply plugged in you can use a 12V supply with some steering diodes installed so that a 9V battery is "blocked" when a higher voltage is applied? I think that's how it's done with lithium battery backup schemes in logic circuits - you could probably Google some schems... Link to comment Share on other sites More sharing options...
psw Posted March 7, 2008 Author Report Share Posted March 7, 2008 You need a way to keep the powerpack voltage from "charging" the battery when applied. Regular batteries, as I'm sure you're aware, do not like being recharged. Perhaps when you have the extrnal supply plugged in you can use a 12V supply with some steering diodes installed so that a 9V battery is "blocked" when a higher voltage is applied? I think that's how it's done with lithium battery backup schemes in logic circuits - you could probably Google some schems... Ok...meanwhile I was checking my power pack socket that I got for my power lead box. It would appear to have three leads one of which (the positive outer ring) is switched/disconnected when a plug is inserted. This again supports the idea of a separate socket and building a lead with power that comes out. This would also give the option of using a separate power pack or the battery or a special lead which carries the voltage and the signal completely separately. I may look into this a little further, I have not heard of those kinds of circuits, I did think though that a fet may be able to be used that senses the power coming into the guitar and then switches off the battery if power is present. Still, a switch is easier for now, the power thing would be very useful if silent, but not the big problem (although I am getting tired of the cost of batteries, not all guitars can easily fit one and performance does suffer as the battery dies). Switching has and remains the bigger problem...specifically the click free operation. I think I have it down to a 3pdt switch, we will see...a shame because a dpdt gives a lot more options and is on a par with the sustainiac device. Still, it is getting more approachable than a full on electronic switching scheme contemplated not that long ago. I don't know how it would accommodate split HB bridge pickups and the like, but for a basic strat it would probably work fine. Perhaps a split HB would only offer a different sound, but given that the phase reverse harmonic switch has little effect, a split to the wrong polarity may be a lot worse. I should worry about this a bit later, a 4pdt switch may address the problem regardless if I can loose the off switch click. My hope at the moment is that by having the neck pickup in parallel with the driver and the ground being constant (never lifted) on any pickup, then the switch off click may well not occur. I am kind of hopeing that since I intentionally send current through both the pickup and driver coils, there wont be the same parasitic secondary coil buildup that requires discharging on reconnection as throughout it is connected...we will see. When I get a chance to draw up where I am at with it, perhaps some clever soul will see another way of addressing things that I have not yet thought of. At this stage I'm curious to see what makes the "thick" driver so usable with sustainiac's systems, so I'll pursue that first before trying to thin it down further. Now that I recall that you may need two 16 ohm coils in parallel to get to the 8 required by a normal amp, I doubt that you could thin it down and fit that on there anyway. Remember, the split coil is half the length and has to cross over between the d and g strings so you will probably need the full depth if this is the case. I don't see how they can run it on <3 ohms, but then perhaps the amp is special or something. Do you know what chip and power rating is actually used. While the patent specifies (in the mid-driver hoover patent) D class amps, I am not sure that they are featured elsewhere in the other patents or their advertising, there is no saying really that anything of the patent is really used in the actual product. Still, it is an obvious way to go, just prototyping these surface mount devices is tricky. I assume that if the windings are the same direction, the magnets need to be in opposite polarity for the scheme to work properly. I would say it is reverse wound reverse polarity like a HB pickup. You don't need to literally wind the coils opposite of course, just the way they are connected. Yes, the magnets need to be reversed though, so it stands to reason that the coils are too, to stay in the same relative phase (pushing or pulling at the same time). Regarding the opening in the bobbin for the pole pieces, it'd be better if the bobbin had six individual holes rather than one continuous slot - when I make the cut I need to have something to keep the two half-bobbins from collapsing once it is split. Most common in cheap pickups these days is a bobbin with poles added later...not supported by the magnets (like true fenders). They can be tricky to remove but you could probably push them out with bolts and a gentle squeeze with a vice and some supporting wood drilled out to support the bobbin so it doesn't crack...this is generally how they are put in there. A slotted bobbin is not so common, but really cheap ones are often like this. It would still work as long as you made two blades to fit so that they didn't collapse. I did expect a dramatic loss of drive with poles and bending strings but it does not seem to have been the case with my pickup drivers. The switching class D amp they use keeps the frequency constant at roughly 30KHz, and reproduces audio frequency variations by PWM-ing the output signal. The inductive impedance at 30KHz is also going to be a lot higher than 3 ohms. I wonder if the very nature of a class-D amp makes it better suited to evening out frequency response variations and problems in our DIY versions because the applied frequency is constant and unwavering? I wonder if they aren't using a car amp type chip or something else aiming for 4 ohms, sometimes you get more power at these ratings, perhaps that is why they can use thicker wire too. From my experiments though, the wire thickness was critical without addressing phase issues (or so the assumption goes), 0.25 wire being too thick even...but then this is a different design and they are pretty specific about the phase compensation circuitry requirements. From the size of the sustainiac board, there is clearly more on there than a simple amplifier...it is quite large. Those giant caps are still a mystery to me also...maybe it is a switch click suppressor...hehehe pete Link to comment Share on other sites More sharing options...
Fresh Fizz Posted March 7, 2008 Report Share Posted March 7, 2008 he switching class D amp they use keeps the frequency constant at roughly 30KHz, and reproduces audio frequency variations by PWM-ing the output signal. The inductive impedance at 30KHz is also going to be a lot higher than 3 ohms. I wonder if the very nature of a class-D amp makes it better suited to evening out frequency response variations and problems in our DIY versions because the applied frequency is constant and unwavering? I don't want to ruin this great thread, but do you know that all the information can be obtained from freepatentsonline? It would be a pity if everybody started to copy the sustainiac. On the other hand I've seen some thingies that could be usefull to us. Like a current-source amplifier to deal with impedance and phase shift, a drive current limiter (to minimize fizz?) and the class D amp. The patent I'm referring to has a three pickup configuration with the driver in the mid position. The switching of this version appears to be active (don't know if that's any good to you, Pete), the driver has it's own preamp to turn it into an active pickup. If you create a free account at freepatentsonline.com you can take a look at the patent images. Taste the forbidden fruit if you wish. Cheers Fresh Fizz Link to comment Share on other sites More sharing options...
utopian isotope Posted March 7, 2008 Report Share Posted March 7, 2008 (edited) Here is another example how to use template to make multiple parts. Red part is ball bearing, that has same diameter as sanding drum. Template doesn't need to be that thick as in animation. Edited March 7, 2008 by utopian isotope Link to comment Share on other sites More sharing options...
col Posted March 7, 2008 Report Share Posted March 7, 2008 It would be a pity if everybody started to copy the sustainiac. On the other hand I've seen some thingies that could be usefull to us. Like a current-source amplifier to deal with impedance and phase shift, a drive current limiter (to minimize fizz?) and the class D amp. I don't think it's anything to worry about. I think there are enough differences in our 'problem domain' that an exact copy of the sustainiac is not ideal for this project. Mostly it's in the circuitry, and how that effects the design of the driver. Although it would be great for us to be able to use class-d tech, I think that for many diy builders its not a realistic option. Thats not because of the difficulty of handling SMD components, its more to do with the requirements for very careful board layout, minimizing certain track distances - basically, to build a class-d circuit other than from an existing design, you need to fully understand the subtleties of the (difficult) theory, and also have access to equipment for small scale soldering, and fabricating PCBs (ideally at least double sided ones). As soon as we decide to go with a more simple drive circuit based on an LM386 or similar, we'll need to alter the design of the driver. e.g. the sustainiac driver seems to have a very low impedance at least at the low end of the desired frequency range, this might be fine for their custom class-d tech, but it will kill a battery driven LM386 circuit pretty quickly, so at the very least, we will need more turns, or thinner wire... If our core has lower 'core factor' than theirs, then more turns is good to give a similar inductance, otherwise thinner wire is a better option. We also have the problem of not having access to bespoke magnets and core materials with specified magnetic properties, so to an extent, each persons driver will have to be slightly different if they want the best functionality with the materials they have available. I think thats enough 'design requirement' that copying the bi-lateral topology doesn't spoil the project. It would be nice if we could come up with some improvements, or different ways of handling some of the many problems, but as far as the basic layout goes, bi-lateral dual core looks like a very good option. It is possible that we can take some benefit from the handbuilt nature of the diy project. e.g maybe we can gain some efficiency from using bobbinless coils wound onto the core. And then there are the possibilities of some of the ideas that have come from this thread - 'thin' drivers, cancellation loops etc. maybe we can apply these ideas to create something different but as good as the commercial units. cheers Col Link to comment Share on other sites More sharing options...
Bonfire Posted March 7, 2008 Report Share Posted March 7, 2008 Hi, I'm trying to build the sustainer from the info contained here. First, I made the driver but my coil has near 7'5ohm in stead of 8ohm, is it bad? should I recoil it again (for the 5th time lol)? Now, I've just built the little-gem amp from here, but I have some doubts. What's the real use of the gain pot? is there any problem if I just use a pcb pot and hide it inside the guitar (in order to not to use it)? Sorry if it was said before, but I can't read all the topic. There was a time when I followed it, but it has grown a lot since that Link to comment Share on other sites More sharing options...
ghendrickson04 Posted March 7, 2008 Report Share Posted March 7, 2008 (edited) Curtisa, to make a split-bobbined (is this a valid word?) driver, I just bought cheap Squier single-coils on eBay. They're cheap and you can just take a thin file and remove the plastic between pole-pieces quite easily. Try to leave a little overhang on the top, however, as winding became a bit of a pain for me. Hope this helps! Bonfire: The gain pot works similarly to the gain on any amplifier. I concealed mine because, ideally, you'll set the volume at or close to maximum and then turn the gain up to boost the volume until you begin to get distortion (or fizz or grunge or whatever you want to call it). That way you can find your maximum clean volume which will better sustain the strings from further away. Edited March 7, 2008 by ghendrickson04 Link to comment Share on other sites More sharing options...
Bonfire Posted March 7, 2008 Report Share Posted March 7, 2008 so it has to be adjusted one time, right? That's what I meant, it's not necessary to have any extra knob in the guitar for the gain Thanks Link to comment Share on other sites More sharing options...
ghendrickson04 Posted March 7, 2008 Report Share Posted March 7, 2008 Sorry, you're right. The gain pot is only a one-time adjustment. It's not necessary to have it exposed on the surface of the guitar. It's an "adjust and forget" pot. Personally, I have the volume pot set up the same way. I find where it sustains cleanly and then stow it so I don't have to worry about it. That and I have a lot of electronics and stuff wired into my guitar and I didn't want to waste space on another pot. Link to comment Share on other sites More sharing options...
col Posted March 7, 2008 Report Share Posted March 7, 2008 so it has to be adjusted one time, right? That's what I meant, it's not necessary to have any extra knob in the guitar for the gain Thats up to you. If you are using a basic fetzer/ruby type of amp, no AGC or other fancy stuff, you might want to have some control over the gain so that you can tweak it depending on the music... also will help to be able to adjust when the battery is getting low. =============================================================================== Been reading through that patent (for the first time - I've only glanced at it in the past) Lots of interesting stuff in there. For Pete, it is interesting to see how they use logic gates to provide a control voltage for FETs for all the switching, and how they do the power up/down in stages to prevent pop (similarly to how I very roughly explained it a while ago). For me the whole idea of a 'current source amplifier' is really cool, gets rid of some of the problems associated with using higher inductances in the driver. I'm going to take a crack at simplifying the circuit as much as possible so it has just basic functionality, and can fit on a reasonably sized piece of board. Not sure if it will work in PDIP sizes on strip board, but you never know until you try. It seems to be what I've been searching for for ages on the interweb - a simplified approach to switch mode amplification. Kinda like a poor mans class-d. It's ironic that what I've searched for many times is right there in the patents... The power supply is interesting - the diode to protect the battery from reverse current(?) is something that we probably should have been using. The patent is interesting as much for the stuff thats not in the final product as for the stuff that is. All that stuff about using the outer turns of the coil to shield from electrostatic coupling - in the final design, it looks as though they went for the more traditional and sensible sheet of earthed copper shielding. I wonder how much of the circuitry has been dumped and replaced with off-the-shelf class-d components. Anyway, lots of interesting stuff to play with - maybe messing with this will give me a better understanding of the intricacies of class-d (I understand the concept, but implementing it is a different kettle of fish entirely) There are a couple of BIG caps, but they're not anything to do with phase adjustments... One filters the battery supply, and the other couples the amp to the driver. The current limiter is similar to some of the AGC things I've been playing with, except it is much simpler because it is limiting a pulse, so not the same worries about rectification and preventing distortion. Maybe someone with a better understanding of this tech can give a more thorough explanation of how the core of the thing works. cheers Col Link to comment Share on other sites More sharing options...
psw Posted March 7, 2008 Author Report Share Posted March 7, 2008 Wow...what a lot of posts in the night... So...welcome aboard new guys, ghendrickson04 and Bonfire and also I see in the last day or so a thousand visits, so hi to the lurkers, feel free to join in Oh, And I unusually mark the points at which significant milestones are past, this time its 150,000 visits to the thread... Sorry if it was said before, but I can't read all the topic. There was a time when I followed it, but it has grown a lot since that I thought you sounded familiar, welcome back then! I don't advise anyone to read it, just join in...you wouldn't read the whole of PG to build a guitar! Ok, so it looks as though a couple of sustainer's are being made on the sly. Good on you Bonfire for finding Biancka's DIY sustainer page and pics plus DIY layout software site. I forget to mention this, this is the same project and good pics plus the fabulous DIY layout software in return for (although it is free) I donated a reel of wire. I was doubly rewarded by the terriffic job he did on a blocked bobbin driver and photo. Look also and download the software and you can get all kinds of guitar related circuits plus specifically the Fetzer Ruby circuit or, use it to tweak and design your own...Direct link to biankas sustainer project page Here's a pic from there... Oh and on the open mail thing I see this... Darkleon: Hey guy! I'm going to build my own sustainer followind your tutorial! Did you find any problem in building it? can you post on the site some sound? Thank you! Darkleon: Ok I've built the driver ( as you did) and now i'm going to assemblate rubyfetzer amp following your schematic. What i miss now is what about the connections.. can you send me a mail? will the sustainer work independently from bridge pick upor i have to splite bridge pickup signal to the ampli? That's not you is it? If not, I guess we will be seeing some more visitors soon. First, I made the driver but my coil has near 7'5ohm in stead of 8ohm, is it bad? should I recoil it again (for the 5th time lol)? This is no problem, a lot of my thin coils range from about 7.2-8.1ohms without much if any difference that you can really hear. It is good to see that you have taken the time to rewind if you don't feel it up to scratch, don't do that for resistance value unless it is right off, only for neatness and build quality. It is not hard to do and every time you wind one you get a little better at it. It is often a good idea to have a few goes to get it right. What did you pot it in PVA? Curtisa, to make a split-bobbined (is this a valid word?) driver, I just bought cheap Squier single-coils on eBay. They're cheap and you can just take a thin file and remove the plastic between pole-pieces quite easily. Try to leave a little overhang on the top, however, as winding became a bit of a pain for me. Hope this helps! Yeah...squire pickups are typically built in this way with plastic bobbins. Mine are high end versions with alnico mag poles, but they could still be removed. @ghendrickson04, why did you need to file the pickups, were you doing a split bobbin bi-lateral thing, or inserting a blade? These days I am content with just the poles, no filing at all! The gain pot works similarly to the gain on any amplifier. I concealed mine because, ideally, you'll set the volume at or close to maximum and then turn the gain up to boost the volume until you begin to get distortion (or fizz or grunge or whatever you want to call it). That way you can find your maximum clean volume which will better sustain the strings from further away. I'd like to mention again the importance of pickup and driver adjustment, this makes a big difference. Especially the bridge pickup, adjust as close as possible to the strings, the driver as practical and depending on the response, back off from the low strings if they are a little too responsive, then adjust the gain settings again. This can make a huge difference to the response and to the amount of clean sustain available, the pickup height in particular is important. You can run the thing completely concealed with only an on off switch. Previously I had advised that on my DIY versions. These days I am using the "drive" control to produce other effects and harmonics and it is invaluable. It is worth playing around with because you may find, particularly if you use distortion that will mask it, that the high gain/fizzy modes are musically useful or just fun to play around with...this could of course be added later. -------------- I don't want to ruin this great thread, but do you know that all the information can be obtained from freepatentsonline? It would be a pity if everybody started to copy the sustainiac. On the other hand I've seen some thingies that could be usefull to us. Like a current-source amplifier to deal with impedance and phase shift, a drive current limiter (to minimize fizz?) and the class D amp. hehehehe....the thread started with a lot of attention to the patents and I have read a lot if not all of the sustainer related and most of the pickup stuff...and there are a lot, check out the one from the 1890's, a sustainer piano, no kidding. On page 7 of the thread I link and discuss a number of useful prominant patents (ebow, fernandes, sustainiac (hoover), etc) but it has come up a lot. Freepatents is one service of many. Google now has a really good one, but I suggest going to the source...USPTO website, use quick search and also, download the imageviewer to see the pics Image software help for USPTO, I use alternaTIFF...all of which is free. USPTO (United states Patents and Trademarks Office) is the source for all these other services and there are patent offices in most countries as well that may be worth a look too. The USPTO will give access to patents to the year dot and also the very latest applications. Also important is the use of the "referenced by" and "cited by" hyperlinks. On a patent...for instance, here is one we often refer to... Sustainiac Patent 5,932,827 Near the beginning of the patent you will see a list of blue patent numbers and dates and names, these are referred to in the patent, by clicking the hyperlink, it will reveal who has subsequently referred to this patent...this is like a treasure trove of related patents from before and into the future...very, very cool...if a little addictive! So, related patents from before and after, with this powerful tool, find one and you can almost find all. As interesting as the patents may be, they can be very confusing to read and can even be purposely misleading. This is not necessarily a description of the actual product as a patent is so expensive they tend to throw in every idea that they may possibly use in products. Sustainiac even have another patent on using a push-pull knob to turn the thing on!!! So, a grain of salt is required. Also, it is in their interest to make it out to be as unique as possible, but if you search around you will find nothing new under the sun and often the older ones will be clearer in explanation...check out floyd rose's patent for instance... Rose, sustainer patent 4,907,483 This explains how he approached the phase compensation circuitry. I am sure I have had lots of patentable ideas but at $30K plus, you would want to be sure that your ideas had commercial potential and you could protect them. Part of what I have aimed to do is simplify the technology and strip back the design and circuitry. My devices have consistently worked very well without phase compensation circuitry. My own circuit and even a fetzer ruby is 4-5 times or less the size of the sustainiac or fernandes circuits. I also have made designs that utilize the neck pickup allowing for normal passive operation of the guitar and all it's pickups, plus the sustainer. My new drivers are also perhaps 20 or more times smaller than equivalent sustainiac and fernandes devices. In short, while the technoilogy is similar, I have taken a different approach. (note however I have spent a lot of time with the patents, but mainly in practical experiments and building to get to this point). I encourage others to do the same if they are seriously going to go down the road of developing their own ideas or picking up on those published on the patents or where ever. If you are following my ideas, like biankia, I wouldn't get to bogged down till you are ready to attempt to take them further. The intent of the DIY design was to make this project approachable to anyone and to bring the technology into the hands of more people as I truly believe it to be a fantastically expressive musical tool and a lot of fun to play. For new comers and lurkers, what I am working on is a proposed commercial "product" of my own. While based on the DIY ideas, it takes it further and is not really suitable for DIY construction. However, never fear, the DIY version can work well with care and attention to detail. For Pete, it is interesting to see how they use logic gates to provide a control voltage for FETs for all the switching, and how they do the power up/down in stages to prevent pop (similarly to how I very roughly explained it a while ago). Ok...so, as i thought...can you give me a basic summary of the stages of shut down described. I really want to create as much of an unobtrusive passive system as possible or a switching system that will work passively when the power is off. The sustainiac guitar does not work properly without a battery at all, with some the bridge pickup may operate but generally it will always need power or the guitar goes dead. Here is an example of good solutions that can be gleaned and possibly improved upon or approached in another way informed by patents. BTW, it is not illegal to identically copy a patent as long as you do it for research and not sale. The original purpose of patents was to disseminate information for the very purpose of furthering technology. Now it is largely a legal instrument effectively preventing it...IMHO! People should bear it in mind that it would be far cheaper and easier to buy a sustainiac itself than to ever attempt to copy it. I can testify to the way the device worked now, and it is very good. I am sure this thread has inspired many to do just that. This is one of many reasons that I am not really interested in building a replica or going down this road too far myself, but there is no reason other's shouldn't or that the DIY version couldn't be "improved" by taking ideas from existing and proven designs. A bi-lateral driver is the driver equivalent of leo fender's split coils featured on G&L guitars and most famously the P-bass to this day. --------------- ah...col has posted as I type, I wondered where that post came from...hehehe...it takes a long time to do one of my posts, a lot of cigs and coffee this early in the morning!!! It seems to be what I've been searching for for ages on the interweb - a simplified approach to switch mode amplification. Kinda like a poor mans class-d. It's ironic that what I've searched for many times is right there in the patents... Oh dear...but I posted a revamp, as per above to page seven with links to various patents...I had assumed that you had at least seen the hoover ones. Try and find the fernandes ones, I forget the inventors name, we had discussed it...an amazing array of driver styles, he did the side driver for instance that fernandes used to use. Also, if you check other sources you will discover people like Micheal Brooks' Infiniteguitar and how sustainiac lifted and refined the idea from him and how sustainiac used to supply fernandes but they ditched them in a bitter battle and went their own way... All interesting stuff, but wont get a DIY sustainer built!!! The power supply is interesting - the diode to protect the battery from reverse current(?) is something that we probably should have been using. All my designs have featured this as a matter of course. It robs a little power, but as I now use a MOSfet, I suspect that putting the battery in back to front may have a disastrous result with this fragile component. Generally, people are safe, I have never blown a LM386 before. ------------ Ok...plenty of post to read there. Each will have to find their own way, but I will suggest again that before anyone gets too bogged down with details and improvements, they really should try a hand at a simple DIY version and make it work. It will work, many have, but if this has failed to get a result then it is unlikely experimental or more elaborate circuits from the patents or elsewhere will help things. If only from a research point of view, having something to improve upon step by step is invaluable. I would also suggest getting a cheap guitar specifically to test ideas on if you are going to engage in a lot of R&D. Here is a pic of my guitar... It changes appearance and pickups, switches and stuff all the time. At the moment the knobs are black for some reason, the tone control is connected and working as a master and I have put a fiveway selector back in there. My little circuit is hanging out the bottom (black with white trim pot) and the driver pickup is now a cheap SC in white instead of this squire one and a different driver coil (hidden under the pickup cover here) and I have added a middle pickup too!. Of note is the "bathtub" pickup route. I use doublesided foam tape to stick the pickups on to a bit of wood and use screws (sometimes) to adjust height. I can easily get the pickups and driver out without removing strings or anything. Such a setup means that it can be tested on a real working instrument (it plays really quite well) and is the most important tool I have in my work on this and has been well worth the investment. Now if you have a working sustainer guitar like this, then it is simple to change the driver for a new design and hear the difference with the same circuit, pickup, guitar and everything else. Similarly, you could change or tweak the circuit, swap the bridge HB for an SC or add a middle pickup. You could even build and test an entire system in this and transfer it fully working into another guitar, the reason I first got this one for. Anyway...I should spend a little more time with the soldering iron and the switching issues of multiple pickup guitars than typing I guess, but I look at this thread as a project in of itself, I am amazed at how much interest there is in it (I remember reaching a thousand visits!!) and how vibrant the conversations and ideas...thank you... pete Link to comment Share on other sites More sharing options...
curtisa Posted March 8, 2008 Report Share Posted March 8, 2008 Now that I recall that you may need two 16 ohm coils in parallel to get to the 8 required by a normal amp Yes, but I'm more interested in trying out the class D switching amp option this time round rather than the classic linear LM386 circuits we've been using thus far Remember, the split coil is half the length and has to cross over between the d and g strings so you will probably need the full depth if this is the case. I don't see how they can run it on <3 ohms, but then perhaps the amp is special or something. Do you know what chip and power rating is actually used. The patent images show a discrete class-D output stage made from a comparator and a pair of N- and P-channel MOSFET drivers. At a switching frequency of many 10's of KHz the amp won't "see" the DC resistance of <3ohms (unlike the linear LM386), as the impedance at that frequency will be much higher - perhaps 10's of ohms? Depends on the inductance of the coils given the number of turns and the laminated core material. Of course, that's not to say I couldn't use a dedicated class D chip amp. It's possible that when the patent was written class D chips weren't as common, and it was cheaper for Sustainiac to roll their own. Most common in cheap pickups these days is a bobbin with poles added later...not supported by the magnets (like true fenders). They can be tricky to remove but you could probably push them out with bolts and a gentle squeeze with a vice and some supporting wood drilled out to support the bobbin so it doesn't crack...this is generally how they are put in there. I just came back from town with a throw-away humbucker that the guys at a music store gave me. The pole pieces on each bobbin are actually one-piece steel running the full length of the pickup, which I think may work to my advantage better than the traditinal six-slug single coil bobbin. I can cut the middle of the bobbins out and re-glue the two ends together to make the shorter bobbins required for the bilateral driver, and they already have perfectly rectangular core windows already moulded into the bobbin. Curtisa, to make a split-bobbined (is this a valid word?) driver, I just bought cheap Squier single-coils on eBay. They're cheap and you can just take a thin file and remove the plastic between pole-pieces quite easily. Try to leave a little overhang on the top, however, as winding became a bit of a pain for me. Hope this helps! Yup, that's pretty much how I made my first sustainer with a solid steel "rail". The donor pickup was a crappy Yamaha single coil with six slugs that I removed and then cut the middle out to make a long rectagular slot to install the new core into. As interesting as the patents may be, they can be very confusing to read and can even be purposely misleading I'm not entirely sure that they'd purposely put in inaccurate information in their patents. It might be out-of-date or superseeded. It's in the company's interest to describe the product fully and accurately so that if they need to demonstrate the system or make a claim against an patent infringement, they can do so in the knowledge that the information is "all there". Otherwise any legal defence will be compromised by innacurate information in the patent. Link to comment Share on other sites More sharing options...
Bonfire Posted March 8, 2008 Report Share Posted March 8, 2008 (edited) Nice to see that you remember me First I tried to make the driver using this magnets I didn't succeed after several attempts, so I left the project... Then I found that great site and I realized how easy was to build the sustainer from a normal pickup, so I tried to get one. I bought a kit from StewMac at last... That's not you is it? If not, I guess we will be seeing some more visitors soon. No, it's not me What did you pot it in PVA? Sorry, I don't understand the question :S (English is not my mother language) That's how my project is right now: I know I've got to protect better the coil I am also having some problems charging the magnets, any tip on it? or just keep on trying until achieving the same power as a factory pickup? I've got to add the pots and repair a broken wire, but that's it. My main problem to finish it all is that I only have one guitar, so any thing I can make can only be a proof of concept. I hope I can buy a project guitar soon. Edited March 8, 2008 by Bonfire Link to comment Share on other sites More sharing options...
Fresh Fizz Posted March 8, 2008 Report Share Posted March 8, 2008 The patent images show a discrete class-D output stage made from a comparator and a pair of N- and P-channel MOSFET drivers. At a switching frequency of many 10's of KHz the amp won't "see" the DC resistance of <3ohms (unlike the linear LM386), as the impedance at that frequency will be much higher - perhaps 10's of ohms? Depends on the inductance of the coils given the number of turns and the laminated core material. Don't worry too much about the switching frequency. Basically it's analog in, analog out (+ distortion). The Mosfets which work like switches don't dissipate power, if they are open there's no current flowing through the mosfet, if they are closed there is no voltage across the mosfet. Now if only one of the mosfets could be closed there would only be 2 analog states, 9 volt and 0 volt. The comparator and switching signal are a way of creating the analog states in between by means of duty cycles. For instance if the top mosfet would be opened for 50% of the time (of a "pulse") the analog state of the output signal would be 6.75. It must be clear to everyone that through this process the signal becomes distorted. (50% of the time 4.5 volt, the other 50% 9 volt). That's the trade-off, more efficiency, less high fidelity. Maybe some of you know the phase shifters built from opamp allpass filters that use mosfet switches (switched resistors) instead of fets. Same principle. Fresh Fizz Link to comment Share on other sites More sharing options...
psw Posted March 8, 2008 Author Report Share Posted March 8, 2008 The patent images show a discrete class-D output stage made from a comparator and a pair of N- and P-channel MOSFET drivers. At a switching frequency of many 10's of KHz the amp won't "see" the DC resistance of <3ohms (unlike the linear LM386), as the impedance at that frequency will be much higher - perhaps 10's of ohms? Depends on the inductance of the coils given the number of turns and the laminated core material. Don't worry too much about the switching frequency. Basically it's analog in, analog out (+ distortion). The Mosfets which work like switches don't dissipate power, if they are open there's no current flowing through the mosfet, if they are closed there is no voltage across the mosfet. Now if only one of the mosfets could be closed there would only be 2 analog states, 9 volt and 0 volt. The comparator and switching signal are a way of creating the analog states in between by means of duty cycles. For instance if the top mosfet would be opened for 50% of the time (of a "pulse") the analog state of the output signal would be 6.75. It must be clear to everyone that through this process the signal becomes distorted. (50% of the time 4.5 volt, the other 50% 9 volt). That's the trade-off, more efficiency, less high fidelity. Maybe some of you know the phase shifters built from opamp allpass filters that use mosfet switches (switched resistors) instead of fets. Same principle. Fresh Fizz Ok...that seems pretty simple, so these mosFETs are swtiching a pulse at the frequency of the strings, is that the deal. Out of interest, what phase shifters work in this way? My simple AGC uses a mosfet in a similar way, if the output exceeds a set level, it will trigger the mosfet to close the signal, a capacitor is used to hold it closed a little while to prevent it from excessively switching...seems to work well and silently. I finally did a rewire to add back in the neck and middle pickups. At one stage I was getting tremendous heat from the circuit, it would appear that when running the neck pickup in parallel with the driver, the direction of the coils are critical, it was fixed by flipping over the driver in this instance. I also got a background high pitched oscillation when turning down the guitar's volume knob that was not present with the volume on max...hmmm. I seem to have fixed this too. However, switching noise remains. Can anyone checking out the patents work out how sustainiac approach this...if there are fet triggered delays, what order are things returned to the system? What is causing the noise? How does one set up fet switching to delay things like this or to drain off stored energy? I will need to do some more work also as it does not seem to be working quite as well as it was, despite the "fixes". I installed a 4pdt switch and have a spdt spare, would switching out the entire circuit, or the whole power supply help do you think? The heating of the circuit was dramatic, specifically the LM386 when wired wrong! I am not sure exactly what the problem was, perhaps the driver was being shorted some how, it was creating a bit of drive. With the harmonic switch switched, it wants to drive the harmonics and will do on the low e, but it is obviously struggling. Perhaps it needs preamp power or something to lift up these signals. My previous versions all had pretty hefty preamps where as this uses only a buffer. Also, if the entire guitar was "active", that is had a buffer or preamp on the output, do people think this could address the switching noise. The idea being that even though the sustainer circuit is being switched out, the guitar is still "powered up". Also, the idea of leaving the circuit in "idle". Someone quoted 4mA, I assume that this is very low, so could you simply switch out the driver to achieve this, or is it the input that needs to be severed to put it in idle? How could one create a simple "mute" switch perhaps. Maybe it is time to reconsider my circuitry in particular the LM386. What do people think of BTL amps, they seem not to require the output caps of something like an LM386. I have been looking at the JRC 2073D for instance to gain extra power and perhaps a cleaner headroom. Really, I'd prefer not to go down this road as my circuitry works really well and without the other pickups there is no switch noise...if that give anyone any clues...it is sooooo frustrating! I really had hoped that putting the pickup in parallel with the driver during operation was going to help things. I seem to have bypassed effectively, but perhaps the middle pickup will need to be disconnected from ground and removed entirely from the system, I should probably have taken the rewire in smaller steps...too much thinking, no enough doing... pete Link to comment Share on other sites More sharing options...
curtisa Posted March 9, 2008 Report Share Posted March 9, 2008 Don't worry too much about the switching frequency. Basically it's analog in, analog out (+ distortion). The Mosfets which work like switches don't dissipate power, if they are open there's no current flowing through the mosfet, if they are closed there is no voltage across the mosfet. Now if only one of the mosfets could be closed there would only be 2 analog states, 9 volt and 0 volt. The comparator and switching signal are a way of creating the analog states in between by means of duty cycles. For instance if the top mosfet would be opened for 50% of the time (of a "pulse") the analog state of the output signal would be 6.75. It must be clear to everyone that through this process the signal becomes distorted. (50% of the time 4.5 volt, the other 50% 9 volt). That's the trade-off, more efficiency, less high fidelity. Yup, I know the design principles behind class D amps, I was more thinking out loud. And the trade off's with distortion decrease as the switching frequency increases (the MAXIM chips for example operate with a switching frequency of 1+ MHz). More importantly, we're not concernened with super high fidelity operation as the amp is feeding a "noiseless" driver. However, switching noise remains. Can anyone checking out the patents work out how sustainiac approach this...if there are fet triggered delays, what order are things returned to the system? What is causing the noise? How does one set up fet switching to delay things like this or to drain off stored energy? The patent shows the guitar as a fully active preamp system for the pickups which runs 100% of the time, and the sustianer circuitry is only switched in via a slow ramp up/ramp down transistor on the supply line feeding the class D amp section (see fig 11 of the sustainiac patent - CR4, R49, C28 and Q8 - it's switching the voltage V4 which supplies the driver amp). The slow ramp up/down is meant to minimise pops in the driver circuitry. Not sure how well it'll work with the old LM386 though. The noise I get when I switch my current sustainer in and out sounds more like a "thhbbpbpbp", which suggests that it's perhaps the chip "motorboating" (low frequency oscillation) as the power supply voltage rises and falls - the LM386 may be unstable if the power supply varies at a (relatively) slow rate. The class D amp may be a different ketlle 'o fish all together when the supply voltage is ramped up and down. Maybe worth a try though? It's only an extra couple of components. Interestingly, many of the dedicated class D chips I've been looking at have a low-power standby option which "poplessly" turns the output on and off, and when enabled (usually by switching a voltage to a single pin on the chip - SPST switching as a possibility?) puts the chip to "sleep" drawing around 0.1uA! In my current sustainer re-exploration, I've pulled apart the humbucker and started re-building it into the bilateral driver. Things are going really nicely at this stage (touch wood) - I've managed to cut the bobbins and re-join them into a pair of half-bobbins, and all the laminations are cut and test-fitted into the new bobbins. I've given the laminations a quick coat of varnish over the exposed edges where I cut them from the donor transformer (to maintain conductive isolation between the lams when they're packed into the bobbin) , and I'm just waiting overnight for them to dry. Looks really neat. I've been taking lots of photos along the way, so hopefully I'll be able to do some kind of photo-essay in the next few days. Link to comment Share on other sites More sharing options...
Fresh Fizz Posted March 9, 2008 Report Share Posted March 9, 2008 Ok...that seems pretty simple, so these mosFETs are swtiching a pulse at the frequency of the strings, is that the deal. No, they are switching at the frequency of 30 kHz. Compare it with a movie projector which projects images at a rate of 50 (?) frames per second. When the thing works you're watching a movie, not a 50 Hz frequency. Exception: dither -> interference between the movement on screen and the 50 Hz thingie. Like when wheels seem to turn the wrong way around. That's one reason why the switching frequency has to be high. Out of interest, what phase shifters work in this way? I can't give you a brand name or schematic but I've seen a schematic with a switched resistor. Then there is a mosfet switch in series with the resistor of the RC part of the allpass filter. (Most of the time it's a fet or photocell/diode in parallel with the resistor.) So when the switched is closed 50 % of the time the resistance will be twice as big. With the harmonic switch switched, it wants to drive the harmonics and will do on the low e, but it is obviously struggling. Perhaps it needs preamp power or something to lift up these signals. My previous versions all had pretty hefty preamps where as this uses only a buffer. The problem is the lousy performance of our output stages. It's the combination of phase shifting and high cut. (My first and not so short contribution) Sustiainac's current drive will work much better in harmonic mode. But what you can do and what I've seen in a patent is use a high boost for harmonic mode. Which means more switching troubles. Another option is to use the current drive principle together with the lm386. This is what the theory says. There's not much more to it than steal a bit of figure 11 of the patent. R26 and feedback loop to C9 into opamp "U1b" (IC U1b should read U2b). By the way figure 10 contains an error, 1001 is in the (negative) feedback loop. Cheers Fresh Fizz Link to comment Share on other sites More sharing options...
psw Posted March 9, 2008 Author Report Share Posted March 9, 2008 Thanks guys for your patience on these things... so these mosFETs are swtiching a pulse at the frequency of the strings, is that the deal...No, they are switching at the frequency of 30 kHz. Ok...so you lost me a bit here. It is amplifying the signal, the frequency of the strings somehow...but it is using pulses of a constance 30kH, so does the current alter as an analogue of the string frequency or something? I know the design principles behind class D amps, I was more thinking out loud....keep that up, cause it helps me The patent shows the guitar as a fully active preamp system for the pickups which runs 100% of the time, and the sustianer circuitry is only switched in via a slow ramp up/ramp down transistor on the supply line feeding the class D amp section (see fig 11 of the sustainiac patent - CR4, R49, C28 and Q8 - it's switching the voltage V4 which supplies the driver amp). The slow ramp up/down is meant to minimise pops in the driver circuitry. Not sure how well it'll work with the old LM386 though. The noise I get when I switch my current sustainer in and out sounds more like a "thhbbpbpbp", which suggests that it's perhaps the chip "motorboating" (low frequency oscillation) as the power supply voltage rises and falls - the LM386 may be unstable if the power supply varies at a (relatively) slow rate. The class D amp may be a different ketlle 'o fish all together when the supply voltage is ramped up and down. Maybe worth a try though? It's only an extra couple of components. Yes, something like this might fix it, or elongate the length of the pop with my luck!!! It is interesting, with a single pickup, I can get it to work with no noise at all. It is only when you try to switch from this single pickup setup back (there is little or no on click) to a passive mode, and a little bit more if it is back to a selection switch of something other than the bridge pickup, that you get this noise. So, do you think a constant preamp is a potential or part solution to the problem? On problem I could see with the slow ramp idea is that there may be a time in which as the circuit is ramping down, that the circuit is running while the other pickups, especially the one under the driver, is still connected. As I say, I only have switching problems with other pickups connected and only really on switch off. So, ramping down on switch off may well mean that the system is working while the other pickups are connected. It is maybe more the case that I need a delay on the reintroduction of these other pickups when the driver is turned off! Maybe it is energy within the output cap (100uF) that discharges at the last moment. Sometimes you get silent switching when switching while the sustainer is powerfully sustaining. BTW, the noise is more of a "thwack" amp off noise, if there is switch on noise it is a small mechanical like click. Someone suggested leaving the circuit on in idle the whole time, woul thins entail swtichin oout the signal/s in to the amp or the driver out. If the driver out were switched completely, would this damage the amp not having a load on the output? Is a projected 4mA an excessive "sleep" mode? But what you can do and what I've seen in a patent is use a high boost for harmonic mode. Which means more switching troubles. I am not sure why this would cause more switching troubles, it wouldn't go towards solving them, but I gather you are talking about a pre-amped active treble booster. I would not be surprised if this was the kind of thing on the "sustainiac" I saw which had a knob that swept the harmonics. I actually found it a much better sound, as with the harmonics I get now simply by boosting the gain) than by the harmonic switch. I did get a reasonable response from the original sustain-o-caster DIY design with the harmonic switch, I used a lot of preamp gain and single coil pickup in the bridge which may have helped... It is an area that I am looking to explore further, once the switching problems are solved, there are a lot of strategies that could refine and alter performance, col has suggested that pure gain may oversaturate the driver for a similar effect. high boost seems likely, I have for a long time messed with output cap values to get different responses. Switching first, although, if the thing needs a preamp, I will certainly be looking at these ideas with this in mind...any links to variable treble boosting preamps and the like...perhaps a one knob active tone control? I may mention that I have the guitar back together, the circuit is again running cool and I have the other pickups working. Playing a guitar with a range of sounds has reminded me of the limitations of a single pickup guitar. A bridge HB simply doesn't have the delicacy of a single coil or the tonal variety of say a strat, fine for rock and stuff, but not so good if playing clean and the working with these more detailed sounds. I would have to assume that you would all have similar switching problems with a multi-pickup guitar. I have assumed (correct me if I am wrong) that you guys do not have any switching noise problems with single pickup guitars...is this right? Ok...so... Interestingly, many of the dedicated class D chips I've been looking at have a low-power standby option which "poplessly" turns the output on and off, and when enabled (usually by switching a voltage to a single pin on the chip - SPST switching as a possibility?) puts the chip to "sleep" drawing around 0.1uA! Yes the mute function...why is it that no one makes a class D in a DIL as a kind of LM386 replacement, or that the LM386 has never really been improved or superceeded? You would think that there would be a market for a small battery operated linear amplifier chip and this thing is amazingly old. What are more knowledgeable people's thoughts on BTL (bridge tied load) amps. I am looking at a JRC2073D for instance, a BTL amp in 8 pin DIL putting out about 2.5 watts, with very few external components and no output caps at all! It is a stereo chip so may be of interest for people powering dual drivers in novel ways too. I found this on it... Of course one of the things about power-amp chips used in battery-powered applications is how much quiescent current they require. A good one will ask for little current until you slam the strings. I've been used an NJM/JRC2073 that I pulled from some cheap computer speakers and it rocks. Long, long battery life and mucho loudness. The 2073, like many of the low-power chips intended for portable stereo device applications, is configurable as a pair of mono devices, or as a single BTL (brideged-mode) channel with more power. from here http://www.diystompboxes.com The application/data sheet even has a muting function circuit for it...a little much for me to fully appreciate. It seems like an interesting candidate for an alternative linear solution. I have tried some alternatives before without too much success and I really don't want to scrap my present circuit that is performing really very well, if it is not going to really "solve" problems. I think that I could work up an interesting design that uses the much function as part of a simple AGC for instance for the 2073, but all that work and still have thse same switch noise would be too much to bear! I have heard rumour that early commercial sustainers suffered some switch noise. However, I don't think this will quite solve the problem if the switching off noise is in fact something unique to this project, for instance stored energy in the unused pickup coils discharging upon reengaging with the passive guitar system. As the noise is only really on switch off (like an amp switching off sound) and only occurs when other pickups are involved, one really has to question if it is a power supply problem surely? If it were, then surely the noise would occur with single pickup installations as well. Can anyone see a way of perhaps staggering the reintroduction of the other pickups (slow release fet or something) or some other way of addressing the problem, or even what the problem might in fact be! I have a great guitar that I want to put the thing in, in fact a couple. Both of these have quality stacked noiseless designs and I wonder if this kind of design would not address the problem with their alternating coils and magnet design. If you recall a post a while back, I reported much improved and different performance (no need to short coils for instance) when using such a design in tandem with my driver design. --------------- So many questions...perhaps I should do lots of little posts and ask them one at a time... Also, we turned the page rather rapidly there, fortunately I quoted fizz's entire last post over the page. However, some may have missed the very nice construction pics of bonfire's new driver and circuit... And... In my current sustainer re-exploration, I've pulled apart the humbucker and started re-building it into the bilateral driver. Things are going really nicely at this stage (touch wood) - I've managed to cut the bobbins and re-join them into a pair of half-bobbins, and all the laminations are cut and test-fitted into the new bobbins. I've given the laminations a quick coat of varnish over the exposed edges where I cut them from the donor transformer (to maintain conductive isolation between the lams when they're packed into the bobbin) , and I'm just waiting overnight for them to dry. Looks really neat. I've been taking lots of photos along the way, so hopefully I'll be able to do some kind of photo-essay in the next few days. It sounds like we are in for a treat here too. Even without going into D-class amps and such, such a driver would likely work well with a linear amp like the f/r for instance, or my circuit. I even suspect that it would work well with just the pickup poles, without the fancy laminated cores and everything, but sometimes, and if you can, it is best to go all the way. The attention to detail (I put nail varnish on my original steel core but it chipped off and is a little rusty now...still works though) in both constructions is likely to pay off down the track. It is often these details that cause squeal or diminished efficiency as people who have made a few and improving drivers of the same design can attest. Anyway...if people can bear with my problem of switching, which I have no doubt will aid everyone who wishes to go beyond a single pickup instrument down the track, I would much appreciate it. My device is working really well, just replaced the battery and has returned to life again, cleaner and more harmonics when the gain is raised, and less distortion for sure. There are encouraging signs that more could be done with it, but as it is it is remarkably good...except for the thwunk when switching the thing off!!! Help!!! pete Link to comment Share on other sites More sharing options...
psw Posted March 9, 2008 Author Report Share Posted March 9, 2008 Oh...just a quick addition... In trying to wire up for multi pickups, I made a mistake which somehow left the pickups in circuit with the driver. A particular combination created an amazingly powerful sound and seemed not to suffer the squeal normally associated with this effect. I didn't take notes and a lot of things changed (I flipped the coil for instance) and this was not what I was trying to do...however, the circuit was receiving a controllable if incredibly loud signal from the driver through the pickup. The result was amazing, but would require a lot of toning down to be usable...a very lively and harmonically rich sound with instant response. Whether the AGC of this circuit was working overtime to control the loud input and so make the thing manageable instead of going into oscillation, or quite how the pickup was wired in respect to the driver, is a little unknown. Certainly, such a set up would be efficient if it could be toned down a little, and the guitar's output was significantly louder. It may mean something, it may mean nothing...it certainly was impressive for the short while it was working like this, but it wasn't doing what I wanted, I spotted the mistake in bypassing and fixed it before I really got a hang of what had happened. I suspect it is something that would only occur with my driver/pickup coil combination design...shades of tesla's free energy....(queue twitlight zone music)...do,do,do,do...do,do,do,do... hehehehe pete Link to comment Share on other sites More sharing options...
ghendrickson04 Posted March 9, 2008 Report Share Posted March 9, 2008 (edited) Let's see if I can figure out the quote thing... Nope...I'll give it a bit more thought later. To quote the old-fashioned way... PSW asked: @ghendrickson04, why did you need to file the pickups, were you doing a split bobbin bi-lateral thing, or inserting a blade? Pete, the reason I filed the top bobbin between the D and G pole pieces was to make a bi-lateral driver with pole pieces. I figured it would be a worthy experiment to wind half to ~3.2 ohms and the other half to ~3.8 ohms to see if I could drive the treble strings a little better with a driver designed this way. Unfortunately, I haven't actually put it in my guitar yet because I've been writing a couple term papers all this last week. I'll give an update when I get around to installing it. Edit: that was stupid of me. I meant ~4.2 ohms and ~3.8 ohms. Spring break starts and all mathematical skills leave. Edited March 10, 2008 by ghendrickson04 Link to comment Share on other sites More sharing options...
psw Posted March 9, 2008 Author Report Share Posted March 9, 2008 hahaha...highlight the text, copy and paste it and highlight it again, then press the quote button. There is a limit to the number of quotes and stuff, so perhaps your way is clearer anyway... Pete, the reason I filed the top bobbin between the D and G pole pieces was to make a bi-lateral driver with pole pieces. I figured it would be a worthy experiment to wind half to ~3.2 ohms and the other half to ~3.8 ohms to see if I could drive the treble strings a little better with a driver designed this way. Ah...yes, well this is how I would do it, or two 16 ohm coils...but I think this would be the best start, I would wind them thin of course, blocking up the lower half as in the pic above...two 16's in parallel may take the entire bobbin and be an unknown quality, two 4's(ish) is a good plan. I too may have gone for a slightly different value with each coil for the same reasons...good stuff! Don't forget to reverse the wires of the second coil, and the magnets, to achieve the rwrp effect. I suspect the magnet's should push out easy enough (especially with the windings removed), or do you have poles and a ceramic magnet...if so, separate magnets may be required for each coil. I discussed a few sources with curtisa recently. good luck...pete Link to comment Share on other sites More sharing options...
ghendrickson04 Posted March 9, 2008 Report Share Posted March 9, 2008 Yeah, I broke the ceramic magnet on accident trying to remove it. I'm going with small magnets on the bottoms of the pole pieces. The first time I wound it I forgot to reverse the winding. I cut it off and rewound and, like I said, ran out of time. Hopefully I'll get around to it early this week. It's my alternative to going the treble booster route to improve treble performance. Link to comment Share on other sites More sharing options...
curtisa Posted March 9, 2008 Report Share Posted March 9, 2008 Ok...so you lost me a bit here. It is amplifying the signal, the frequency of the strings somehow...but it is using pulses of a constance 30kH, so does the current alter as an analogue of the string frequency or something? I know the design principles behind class D amps, I was more thinking out loud....keep that up, cause it helps me Fresh Fizz's analogy with the cinema projector was quite good. The MOSFET's push and pull current through the load (the driver) in a squarewave at very high constant frequency (has to be much higher than what is audible). Audible sound in the load is reproduced by varying the duty cycle of the square wave in direct proportion to the input signal. The inductive nature of the load provides a filtering effect, smoothing out the variations in the duty cycle and we percieve the effect as sound. If the duty cycle remains constant we hear nothing. DC motor speed controllers work on the same principle - by varying the duty cycle of a fixed frequency squarewave you can vary the amount of "average" voltage applied to the motor, thus varying the motor rotational speed. Because the MOSFET driving elements are either fully on or fully off (creating the squarewave), ohms law says that the power dissipated in the amp will be extremely low (MOSFET fully on, R=very low, V across MOSFET=very low, P=V^2 / R is also very low; MOSFET fully off, no current flow in MOSFET, no power to dissipate). Getting back to FF's projector analogy, each frame of the footage is only shown for a fraction of a second. If the frames are shown fast enough our eyes "filter" out the flickering and we see the result as fluid movement on screen. Yes, something like this might fix it, or elongate the length of the pop with my luck!!! Easy enough to try though. It could also just be that the LM386 becomes unstable driving the load if the power supply voltage suddenly disappears. It is interesting, with a single pickup, I can get it to work with no noise at all. It is only when you try to switch from this single pickup setup back (there is little or no on click) to a passive mode, and a little bit more if it is back to a selection switch of something other than the bridge pickup, that you get this noise. Just thinking about this now, this could be another drawback of the transforming effect of the driver/pickup stack. The pop (or "fart" I'm getting) could also be caused by the disconnection of the driver and simultaneous re-connection of the pickup winding while the driver is still being driven. The transforming effect of the combo system produces lots of volts (at very low current) in the pickup winding as we've already proven. If the pickup is reconnected to the system before the induced voltage on the pickup winding has had a chance to settle down to zero you'd get a pop. If you're only running with one pickup you probably wouldn't have this problem as you're not attempting to re-connect the combo pickup back to the system, and so the voltage across the pickup winding has a chance to decay naturally Why it seems worse on pickup selections other than the bridge I'm not sure. Perhaps it's the physical distance between the driver and the selected pickup which exacerbates the problem? You could also be looking at some kind of EMI pulse from the driver when it's disconnected, maybe even the back EMF in the pickup winding, that could be picked up by the "closer" pickup? One way I can see to get around this is perhaps utilising some kind of staged switching sequence. When the sustainer is turned on: 1. the combo pickup is disconnected (and possibly shorted out), 2. input signal to driver amp is set to zero, 3. power is applied to driver amp (possibly even with the slow ramp circuit), and 4. input signal to driver amp is gradually raised up to nominal (over maybe 10mSec or so). The power-down sequence would be the reverse order. Obviously you're not going to be able to do this with mechanical switching, so you're looking at a FET for the light duty switching operations (driver input signal fade in/fade out), a transistor for the power supply switching, maybe a relay or some other high-voltage transistor switch for the pickup leads (FET's are probably too fragile to cope with the big voltages induced by the driver combo), and something to perform the sequenced switching (maybe an 8-pin PIC?). There may be a way to do it by some kind of zero-crossing detector aswell, so that the driver signal is turned on and off when the input signal passes through 0V. Maybe triggering via TRIAC's? I dunno. Probably getting a bit too complex for what you're wanting I suspect? So, do you think a constant preamp is a potential or part solution to the problem? Only because it enables you to do fancy switching operations like I described above. Plus sustainiac describe using the driver as a pickup in itself which requires a special preamp to boost the signal up to normal guitar levels. Someone suggested leaving the circuit on in idle the whole time, woul thins entail swtichin oout the signal/s in to the amp or the driver out. If the driver out were switched completely, would this damage the amp not having a load on the output? Is a projected 4mA an excessive "sleep" mode? Shoudn't damage the amp, no. 4mA constant drain on a 9V battery might be a little steep, although the datasheet doesn't mention if that 4mA is with or without a load connected. You might find that the quiescent current drops if the chip is feeding no load. And anyway, if I'm right about my theory about the transforming effect of the combo setup, the sudden disconnection of the driver while the amp is still running would still cause the sudden back EMF in the pickup winding, resulting in the "pop" or "thump". You'd still need to do some sequenced switching and signal ramping to get around it. Yes the mute function...why is it that no one makes a class D in a DIL as a kind of LM386 replacement, or that the LM386 has never really been improved or superceeded? You would think that there would be a market for a small battery operated linear amplifier chip and this thing is amazingly old. Yes, class-D in only SMD outlines is a pain I agree, however there are means and ways of manually soldering SMD chips out there that I'm hoping I can perform myself. The LM386 is probably so lasting because it's so common and easy for anyone to use. It also finds use in ohter areas like servo drivers and oscillators, which class D chips can't really do without a lot of other support components. What are more knowledgeable people's thoughts on BTL (bridge tied load) amps. I am looking at a JRC2073D for instance, a BTL amp in 8 pin DIL putting out about 2.5 watts, with very few external components and no output caps at all! It is a stereo chip so may be of interest for people powering dual drivers in novel ways too. Dunno about the 2073, it looks like quite an old chip. Can you still get it? There may be other ones out there that do the same thing but better. I think Col found some TDA7xx things that might be better suited. I can't see anything on the datasheet that suggests this chip has a muting function, although it does say that it has "zero turn-on noise". The muting function is handy as it'll eliminate another fancy sequenced switching element. With the chip in mute mode you can probably switch the thing on and off without having to worry about pops and thumps (no signal output, no voltage across the sustainer, no voltage stepped up via the pickup, no pop...maybe...). If you can find a BTL linear amp that has the muting function I'd grab one for experimenting with. It's normally only a single pin that is either tied to ground or the supply via a switch. Link to comment Share on other sites More sharing options...
psw Posted March 10, 2008 Author Report Share Posted March 10, 2008 I can't see anything on the datasheet that suggests this chip has a muting function, although it does say that it has "zero turn-on noise". It is an add on circuit thing on the second page or so, not a separate function as on some chips...check it out...i'd post it, but it's a PDF, so a no go... My interest is that some have suggested that part of the problem is in the output cap, but these don't exist in this circuit...but I may be clutching at straws here. I also hoped that running the driver and pickup and the middle pickup circuit and bridge pickup permanently to earth would help, but apparently not. Why it seems worse on pickup selections other than the bridge I'm not sure. Perhaps it's the physical distance between the driver and the selected pickup which exacerbates the problem? You could also be looking at some kind of EMI pulse from the driver when it's disconnected, maybe even the back EMF in the pickup winding, that could be picked up by the "closer" pickup? It's good to see that you are starting to get a handle on the problem. I don't know what it is, but the later is a favoured suggestion. Back EMF in the pickup coil flowing back through the ground and or hot leads of the pickups when reconnected. Clearly a problem with the extra pickups. Perhaps the bypass function is a bit ambitious, I suppose I'd be content with it as a function only with the selector in the bridge pickup position, but the noise is typically present there too. If I can't solve it with this circuit, it is unlikely that I will be able to solve it with a different amp as it would appear that it isn't the switching off of the circuit is the problem if there is no noise with one pickup but something to do with the driver and nearby pickups or the pickup/driver stack as you suggest. As I say, I was skeptical but I had hoped that keeping the ground connection in the new scheme and actively running power through the pickup in parallel with the driver would help...apparently not...grrrr I dunno. Probably getting a bit too complex for what you're wanting I suspect? Way too complex, really I am prepared to do some electronic switching, but until I can identify what is causing the problem, I wouldn't even know the plan to address it. Yeah, I broke the ceramic magnet on accident trying to remove it. I'm going with small magnets on the bottoms of the pole pieces. The first time I wound it I forgot to reverse the winding. I cut it off and rewound and, like I said, ran out of time. Hopefully I'll get around to it early this week. It's my alternative to going the treble booster route to improve treble performance. Well...never mind, a pickup ceramic wouldn't work anyway for a bi-lateral. Better to get separate magnets as you suggest and reverse half of them...that's what I would have done anyway! Ahhh...reverse winding doesn't have to be literally wound the other way, it just means you reverse the wires on one coil to the other so the current runs in the opposite way...just like reverse phasing a coil, you just swap the leads over...oh well, you will have had lots of practice. I was under the impression that treble performance was the least of your problems, as I understood it, everything was coming out in harmonics everywhere. I really think the whole preamp massive amp powersupply and the treble booster and possibly an inefficient driver, or elements more or less of all these things are symptomatic. You don't need a bi-lateral design to get high string response, but you do need a good solid construction. Too much power may account for some of the harmonic response, I dare say the diode clipping would add to this remarkably. All these things my well make for interesting "effects" but probably wont help in getting the basic effect desired at all...IMHO. Bettter to get the thing working via conventional means and then test your theories for improved responses and performance than to rely on these unproven methods from the outset. Make sure your winding and potting is really well done, nothing like internal vibration to kill high string response. Also, high string response has always been the first to suffer if you are using the wrong wire for the design....as I say, I specify 0.2mm for basic thin wound single coil drivers. I predict that a bilateral wired as you describe to be very similar in specifications. Parallel coils of 16 ohms or other designs...well who really knows. It took a lot of trial...and mostly error to arrive at this for me, expect the same for yourselves. 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). The fact that it doesn't occur in a single pickup setup (as I say, you guys have never mentioned it) must be a clue. Unfortunately, for some reason I can't fathom, I appear to be the only one of many who even desire to make it work on a conventional multi-pickup instrument, so I do feel a little on my own and only in the most recent posts have people even seemed to grasp the problem at hand. Keep at it if you can bear it, I really don't get where the problem actually is emanating from... pete Link to comment Share on other sites More sharing options...
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