disndat Posted February 10, 2008 Report Share Posted February 10, 2008 Well the main reason is I have another variax transplant,and two I dont need the switching and all the other stuff of the fernandes.I think the main problems you guys are having has to do with rf and switching the unit in with your other pickups-I dont have that problem. Link to comment Share on other sites More sharing options...
utopian isotope Posted February 10, 2008 Report Share Posted February 10, 2008 (edited) Some thoughts again.. @col: If I remember right, you are using sustainer, that has an AGC? If so, does it have a "pick filter" -properties in it? ------------- @col and psw: When you pick a string or hit chord, there is always signal peak, before string(s) settle and vibrate at their fundamental note. That peak goes to sustainer and is amplified(unnecessarily?) too, causing less efficiency. ---------------------- It came to my mind when testing things and listening some live recordings. Feedback really doesn't seem to start at the time you hit string(s), unless you have some uranium-core pickups and wall of amps that go to 11. ---------------- Anyway, I'm sorry if this subject is discussed earlier. Tried that topic search with word AGC, but it doesn't seem to allow that short acronym. --------------------------- @disndat: This thread just might be focusing more on DIY, rather than modifying readily available commercial products. Browse and read this thread, if you want to know more about the essence of sustainer. And maybe post some audio for us to listen as a reference. Edited February 10, 2008 by utopian isotope Link to comment Share on other sites More sharing options...
col Posted February 10, 2008 Report Share Posted February 10, 2008 Well the main reason is I have another variax transplant,and two I dont need the switching and all the other stuff of the fernandes.I think the main problems you guys are having has to do with rf and switching the unit in with your other pickups-I dont have that problem. Pete is busy trying to perfect a massively complex switching arrangement, but not me I just use a pickup and a driver and that's all. there is an on/off switch and a mode switch. Personally, I don't see the switching as being problematic - it's no different from designing switching and controls for a guitar or for a stomp box - same kinds of compromises between aesthetics, usability, flexibility and functionality... sure, it will take a bit of time and testing to get it just how you want it, but thats to be expected. We don't have any problems with rf. The issues we have a related to a bunch of things - as far as we know, they are internal problems caused by the sustainer system itself. Right now, we have no complete solutions to the issues we have, only different systems based on different compromises that each of us have accepted. If you really do want to try this project, first build a basic fetzer/ruby and a 'standard' driver - e.g. single coil around a bar of magnetic steel, with a magnet on the bottom, the coil should be 0.2mm winding wire and have a resistance of around 8ohms... for me that meant about 140 turns of wire (I used 0.23 wire)... wire should stay within the range 0.18 - 0.25. When you have that built and working, you will get a better idea of how useful the project is to you. Then would be a good time to start asking about other more esoteric stuff like dual core drivers, AGC, piggybacking etc. If you want something thats just going to 'work' without experimentation, tweaking, R&D, iteration etc., then come back again in a year and see if we're there yet - otherwise, welcome BTW, we REALLY would appreciate some demo clips of a Fernandez sustainer doing its thing If you're up for it, it would be best to avoid fancy playing etc. stick to long notes.... examples of the different modes would be nice, and ideally (for me anyway) some clear demos of how it works on a completely clean (no distortion) sound. Also, if there are any weaknesses, examples of them would be good. If you can do this, then it will be MUCH easier for us to tell you if this project is up to the standard that you are used to! (www.soundclick.com is a good place to upload mp3 clips) Col Link to comment Share on other sites More sharing options...
col Posted February 10, 2008 Report Share Posted February 10, 2008 Some thoughts again.. @col: If I remember right, you are using sustainer, that has an AGC? If so, does it have a "pick filter" -properties in it? Depends what you mean by: 'a "pick filter" -properties' @col and psw: When you pick a string or hit chord, there is always signal peak, before string(s) settle and vibrate at their fundamental note. That peak goes to sustainer and is amplified(unnecessarily?) too, causing less efficiency. hehe, this topic has been worn out in the past lol What you say is true IMO, assuming that not having drive during the initial loud part of the sound doesn't have a negative impact on the 'alive' quality of the sound. Personally, as I learn more about the intricacies of how a sustainer works, my view on this keeps changing and right now, I'm not sure either way. My current system doesn't drive the strings until the initial attack is over because of the way the AGC is set up. This works well, but it gives a different feel and a different sound to non AGC systems - one thing it certainly does have going for it though is efficiency. Pete has recently reported a 'ringing sound' during the attack portion of the note. This goes away when he turns the driver gain down a little. What I think is happening here is that initially, the strings natural momentum due to picking the note and the force applied magnetically by the driver are not 'tuned in' to each other, in some cases with certain notes on certain strings, they can be fighting against each other. If the gain is lower, what you get is a little dip in volume as the driver causes some damping, and then as the energy in the string quickly dissipates, the driver takes over.... This happens on my system as the sustain kicks in - there is a small dip in volume, a bit like you can get with a compressor. If the gain is set high enough so that the driver can nearly match the natural attack energy, there can be oscillations which sound like a ringing noise... I suppose the ideal would be to have subtle AGC to avoid just the loudest part of the attack phase, and have the gain just low enough so that all other ringing is avoided. There are a bunch of other related things that I've been studying recently, but I'm writing them up in almost an essay style, because theres just too much to post, and it's not just ideas and questions, there are a lot of answers as well. So I'll see how I get on with that before posting too much of it here. I will most likely try to include lots of other stuff about how the system works, what the options are, what the issues are and what possible compromises and solutions exist. This won't be a 'how to build a sustainer' thing, but it should be a pretty good information doc for folks who want a better understanding of how a sustainer works (at least the type we are working on) It came to my mind when testing things and listening some live recordings. Feedback really doesn't seem to start at the time you hit string(s), unless you have some uranium-core pickups and wall of amps that go to 11. Very true - feedback, usually takes time to 'bloom'. This is something I was exploring when I started working on AGC based designs. My initial reason for wanting a sustainer was to mimic what happens with a loud amp, but with just headphones or into the computer... its not quite as simple though (what ever is?) What about the stronger sustain and the warm singing full bodied tone that you get from a loud amp ? It doesn't have any lag - you get it from when you hit the string! and it is arguably even more important then classic 'feedback'! If this effect can be produced (at least in part) by a sustainer, then its unlikely to work if the sustainer doesn't kick in until natural feedback would start to occur (this is a limitation of my existing system, so I am talking from experience) Anyway, I'm sorry if this subject is discussed earlier. Tried that topic search with word AGC, but it doesn't seem to allow that short acronym. No problem. Its always good to revisit these ideas and have another look at them - luckily thats exactly what I've been doing over the last few days If you want to find earlier AGC related discussion, here are a few search words to try: automatic gain control lm13700 dynamic range inversion limiter compressor threshold my circuit ( :D) cheers Col Link to comment Share on other sites More sharing options...
disndat Posted February 10, 2008 Report Share Posted February 10, 2008 First let me be clear that I am NOT trying to modify the fernandes but replace it.There is a guitar player named jeff miller that has a les paul with variax guts that shot a video demoing the clean sounds with a sustainer-look for it on the line 6 boards.I will take your advice and build the ruby circut and my own driver. Thanks Link to comment Share on other sites More sharing options...
psw Posted February 11, 2008 Author Report Share Posted February 11, 2008 I only have a minute...may post later... first though. I don't think you will find anything by searching as if it is in this thread, which it is, the search function will bring up the whole thread...not the relevant post...a big problem finding things now the thread is soooo looooong... Also... I have been experimenting today... I tried the new concentric wound driver...interesting, some potential. I certainly worked but lacked power (needed a whole lot more applied, but still within the scope of the LM386's gain. Quieter and seemed to need to be adjusted closer...and more true to the fundamental...less harmonics....hmmm Also...I had been working on an ussumption with new switching options that I had tied the unused pickup coil together for convieniace/because I could... However...I am testing on the same guitar with same circuit and the neck pickup on which the driver sits is not connected to anything and left open. If the pickup leads are connected, there is a radically different response...less harmonics and less power, less noise too. With the neck pickup wires open, there is at least twice the power and quite a different harmonic response compared to shorted together (still not connected to anything else). Quite bizarre. The driver setup does not like the harmonic mode, requiring the power to be decreased a lot and then only responds properly on the lower strings...hmmm Anyway, a very interesting observation and perhaps important...what do others make of this and what is going on here... pete I will try and get back soon on the other recent questions...have to run...p Link to comment Share on other sites More sharing options...
curtisa Posted February 11, 2008 Report Share Posted February 11, 2008 If the pickup leads are connected, there is a radically different response...less harmonics and less power, less noise too. With the neck pickup wires open, there is at least twice the power and quite a different harmonic response compared to shorted together (still not connected to anything else). Quite bizarre. The driver setup does not like the harmonic mode, requiring the power to be decreased a lot and then only responds properly on the lower strings...hmmm This has been already touched upon some time back. The driver/pickup stack is essentially a transformer - the "primary" is the driver coil, the "secondary" is the pickup winding, the "core" of the transformer is the pole piece(s) of the pickup which the driver is wound on to. The transforming effect of the driver/pickup is just like a step-up transformer - the signal being pumped into the driver winding is stepped up by the pickup winding. Shorting the secondary of a power transformer will result in lots of current in the primary, low or no voltage on the secondary, and excess heating (and losses) in the windings, more than likely resulting in eventual destruction of the transformer. Shorting the pickup winding out while using the driver will affect the driver in some way, be it reduced output, strange frequency response, and/or all sorts of other unpredictable behaviours. It may be advantageous to terminate the pickup winding into some resistive load when in sustainer mode, rather than leave the pickup either fully shorted or fully open, maybe 100k or so. I found in my sustainer I had to short out the pickup winding because when the pickup leads were left open-circuit it would feedback really badly, presumably because I was stepping up the driver signal via the pickup and radiating all kinds of crap into the guitar cavity. But I'm pretty sure I could get a better sustaining action if the pickup winding wasn't shorted dead, maybe loaded just enough to be just under the point of feedback. I don't think shorting the pickup winding will result in destruction of the pickup (as for the power transformer) as the source impedance of the pickup winding is quite high and no damaging currents are likely to be flowing through the winding, but I do think that it may be better to run the unused winding into some load. Link to comment Share on other sites More sharing options...
psw Posted February 11, 2008 Author Report Share Posted February 11, 2008 Link to comment Share on other sites More sharing options...
col Posted February 11, 2008 Report Share Posted February 11, 2008 first though. I don't think you will find anything by searching as if it is in this thread, which it is, the search function will bring up the whole thread...not the relevant post...a big problem finding things now the thread is soooo looooong... hmm, I've found that by using the search topic box at the bottom of each page, I can very successfully search for individual posts within this single thread (thats what its for ;p) I can usually find any particular post or discussion I'm looking for from way back when within a few minutes... assuming of course that I can remember the topic under discussion e.g. go an put LM13700 into that search box (at the bottom left of this page), you should get about 3 pages of results - certainly a manageable quantity... then when you found the post in the results, click on the 'Post Preview' link under it to jump to the parth of the main thread it came from. cheers Col Link to comment Share on other sites More sharing options...
utopian isotope Posted February 11, 2008 Report Share Posted February 11, 2008 (edited) "first though. I don't think you will find anything by searching as if it is in this thread, which it is, the search function will bring up the whole thread...not the relevant post...a big problem finding things now the thread is soooo looooong... hmm, I've found that by using the search topic box at the bottom of each page, I can very successfully search for individual posts within this single thread (thats what its for ;p) I can usually find any particular post or discussion I'm looking for from way back when within a few minutes... assuming of course that I can remember the topic under discussion e.g. go an put LM13700 into that search box (at the bottom left of this page), you should get about 3 pages of results - certainly a manageable quantity... then when you found the post in the results, click on the 'Post Preview' link under it to jump to the parth of the main thread it came from." cheers Col Thanks for the searching tips. ------------------------ psw wrote:"With the neck pickup wires open, there is at least twice the power and quite a different harmonic response compared to shorted together (still not connected to anything else). Quite bizarre. The driver setup does not like the harmonic mode, requiring the power to be decreased a lot and then only responds properly on the lower strings...hmmm" That reminds me of an electric motor; if you spin its axle when leads aren't shorted, it rotates more freely when compared to leads shorted-situation. When shorted, it resists spinning much more. Shorting coil(s) seems to "freeze" their magnetic field in some way. I assume that shorted pickup does something similar to the strings. ----------------------------- col wrote:"What about the stronger sustain and the warm singing full bodied tone that you get from a loud amp ? It doesn't have any lag - you get it from when you hit the string! and it is arguably even more important then classic 'feedback'! If this effect can be produced (at least in part) by a sustainer, then its unlikely to work if the sustainer doesn't kick in until natural feedback would start to occur (this is a limitation of my existing system, so I am talking from experience)" Yep, you are right. But to get more live sounding feedback, some overdriving is necessary at some stage? Of course it depends on what kind of sound you like. Some examples of my favourites are live sounds from Jimi, Jimmy Page, Pete Townsend, Santana and Tony Iommi. Quite raw stuff, but all of those use fuzz/distortion/overdrive, so that feedback is easier to produce. And also easier to imitate. Maybe some day I make some samples and post them here. Edited February 11, 2008 by utopian isotope Link to comment Share on other sites More sharing options...
psw Posted February 11, 2008 Author Report Share Posted February 11, 2008 hmm, I've found that by using the search topic box at the bottom of each page, I can very successfully search for individual posts within this single thread (thats what its for ;p) well ...golly...I guess I never searched for something while the thread is open or something...geee...well, no more complaints about long posts then, that will help... That reminds me of an electric motor; if you spin its axle when leads aren't shorted, it rotates more freely when compared to leads shorted-situation. I will have to try that...no, I have never come across it nor read about that phenomenon... So is the implication then that shorted pickup leads (secondary coil) diminishing the driver's power or boosting it? If so, the ultra thin driver coil is substantially more efficient/powerful than previous designs (I don't ever recall not testing the thing without a pickup as it is integral to the design...if it implies a boosting effect, then even a stand alone coil would benefit from an unused open secondary coil. The likely hood of free power seems remote if not contrary to the laws of physics. Does anyone know where I can learn more about these kinds of effects, such as the electric motor observation that is easy to understand and digest? Yep, you are right. But to get more live sounding feedback, some overdriving is necessary at some stage? Of course it depends on what kind of sound you like. Overdrive can enhance the sustain effect of a sustainer. For instance the compression of distortion can bring up the high harmonics that are less audible without it and a wha and other effects can make these things a little more selective (just as with real feedback). You don't need or particularly want the sustainer to produce the distortion, that can come from the amp or effects anyway and usually sound more musical than something that risks EMI contamination or contains stray unrelated artifacts from the sustainer system (such as those produced by loose winding in the driver for instance). The beauty of the sustainer though is that it can produce these effects (regardless of clean or distortion), at any level (or none in a recording situation) and that, unlike loud amp feedback, the results are predictable and repeatable with confidence. I read an article once with Gary Moore where in making his "blues alive" album, he has an amazingly long note held with feedback at the climax of the tune 'parisienne walkways', in sound check he tested it marked the spot on stage where it worked and everything but when it came to the concert, it didn't work because the people in the theatre dramatically changed the acoustics...I think he said he hit the note 13 times or something before he got it and just edited out the false starts. A guy like santana has a whole style built around controlled feedback sustain and is obviously a master of its use. On rare occasions he uses a different sound (eg...'I'm winning') you can tell by his phrasing that it is santana, but those halmark long notes are gone. Obviously his sound and equipment helps (although he got it at woodstock with an SG, so a PRS isn't necessary) but more that he has mastered control over years and years of playing loud I suspect. Clean sustain and harmonics though is a pretty unique effect and can take the guitar into another area and is desirable. If fizz and distortion is a necessary part of the sustainer working, then I suspect that there are failures within the system. -------------- To address some previous posts.... Welcome ghendrickson04 / Garrett That's great. I have found that perhaps you don't really need any appreciable preamp gain and a buffer is adequate. If you have reasonable output pickups and a good driver, perhaps something like the stock ruby circuit is a good choice. The fetzer / ruby has been used a bit, but has extra complications with having to bias the transistor. A general LM386 circuit (often found in a kit even) but with the addition of a buffer or preamp to prevent loading (important) should be all that is required. My new circuit has no preamp gain, in fact the AGC is a limiter, yet I now find that perhaps even this is too much with the LM386 on minimum power. Don't be fooled into the idea that a more powerful amplifier or stronger magnets is the way to go on this, it is something of a balancing act and more power means generally, more EMI...greater efficiency and less power is the better strategy IMHO. welcome back disndat...you've been here before as I recall? Hey guys I have a variax that I transplanted to a strat.I bought a fernandes sustainer and I use it with just the single coil driver and I drive it from the analog output of the variax(no bridge humbucker required).It works great.My question is could I use just the ruby circuit and a wound driver and drive it the same way as the fernandes?I would like to simplfy things and I only need standard and harmonic modes(no use for mix mode).I would like a 3 way toggle(les paul type) to switch from off to standard to harmonic.Any thoughts?Col, Pete? Thanks for any info That's some important work and I'd like to know more about how it hooks up...the variax has an analogue output? It is unchartered waters, but so I assume would be fitting the fernandes sustainer too..and you have been able to do that! There is no reason not to assume that it wouldn't work in the same way. However, to use a standard LP like three-way switch (or were you considering something else like a strat like blade or toggle?) is going to be a little tricky. If you like the fernandes, can afford it or there no other reason not to use it, then col is right that perhaps stick to what you know. Alternatively, the fernandes has a largish circuit and fixed switch positions, so perhaps something like the sustainiac model would be better suited. They appear to use electronic switching (both companies actually) and since you have constant power to run the variax (I assume you don't run the whole thing simply on batteries do you?) I think the sustainiac models allow more switching options (like push pull pots). I am not sure if anything though will work with a standard LP like three-way. I suspect that a three-way mini dpdt toggle could be wired for middle off and different modes to either side...I may even have posted such a scheme, I know I was working something out. What I have always wanted to achieve is a single knob sustain controller. I'd like to see a push pull knob or something that you pull up for on and a range of sustain and harmonic effects produced along the spectrum of this control, making the harmonic switch obsolete. What recent posts seem to imply...and I will have to do a little more experimenting along the lines curtisa implied with adding loads...is that this may well be achievable simply by altering the load of the unused pickup/secondary coil of the pickup/combo. If not, I had already posted ideas of variable or switchable output caps to produce such effects too. Any further thoughts along these lines would be appreciated and some testing of these ideas likely. ------- Work is a little slow on this, it always seems to be these days...but I am getting some interesting results. What I haven't yet done is get the guitar back to a fully working state...the neck pickup is totally unconnected to anything. There may well be trials ahead when it is reconnected and bypassed as when the thing is turned off and the neck pickup ground is reconnected, perhaps we will see a return of the dreaded "off switching click" symptom never solved with the original sustain-o-strat. Mind you, on that guitar the pickups are grounded together (both neck and middle) when on...perhaps a solution and improvement is in the addition of a load instead of a wire bridge. I also wonder the effect of a pot/cap tone control like arrangement for the secondary coil load...perhaps such a thing will provide even more range of secondary coil resonance effects. I spent some time last night devising a scheme wherein the on/off bypass switch could be economically devised to switch in a pot or load, instead of a short when on, and appear to have it down to a DPDT switch for a two pickup guitar. The implication then if this works is that a push-pull pot may indeed work to turn it on, and that pot also be used to adjust the secondary coil resonance effects. It is possible though that a special dual gang pot may be required (also possible) to enable gain to be increased along with the loading effect as the coils are shorted to compensate for lack of power...it will be a tricky balancing act I suspect. anyway...better be off... pete Link to comment Share on other sites More sharing options...
col Posted February 11, 2008 Report Share Posted February 11, 2008 hmm, I've found that by using the search topic box at the bottom of each page, I can very successfully search for individual posts within this single thread (thats what its for ;p) well ...golly...I guess I never searched for something while the thread is open or something...geee...well, no more complaints about long posts then, that will help... hehe, don't worry about it - I only found it through luck when I wasn't searching for anything. It's a really bad piece of user interface design IMO. It should at least be available at the top of the page. Even worse than that, it has an ambiguous title... 'Search Topic' could mean search for the topic you are interested in.... what it should say is 'Search This Thread'... I'm sure with that title and a more prominent position it wouldn't have been missed.... although, I guess its not top priority as most threads won't get beyond a few pages. Something else I worked out is that it's possible to create a bookmark that always starts you only the last page of the thread: http://projectguitar.ibforums.com/index.ph...iew=getlastpost At least I found that useful (the URL is truncated by IP.Board, but if you right click it or look in the status bar, you'll see it in all its verbose glory) That reminds me of an electric motor; if you spin its axle when leads aren't shorted, it rotates more freely when compared to leads shorted-situation. I will have to try that...no, I have never come across it nor read about that phenomenon... If you think about it, it does make sense - also the stuff about shorting the ends effecting the driver differently to keeping them open.... We know that moving a wire around near a coil creates a current in the coil, and that a current in a coil creates a magnetic field... with out these effects there would be no sustainer (or motor). If the coil is disconnected, the circuit is broken, (you might get some build up of charge? enough for sparks?? anyway) no current flows. However, if you connect the ends to each other, you make the circuit and a current will flow when either the string vibrates, or more importantly, when there is another coil nearby with a current flowing in it! So if the ends of the pickup coil are connected to each other, the signal in the piggyback driver will cause a current in the pickup coil to flow, and the pickup coil will develop a magnetic field... Is that field going to oppose the drivers field ?I haven't searched the net or in a book then sat down and worked it out... My guess is that it would oppose it, because the energy for the pickups parasitic magnetic field needs to come from somewhere... so it must be sucked out of the driver... damn leaches these pickups are... does that make any sense? ---------------------------------------------- WARNING - you are now entering teaser territory! As for the other stuff about possible benefits of clipping in the drive signal etc. I have some interesting (very) ideas about that issue and other related topics. These ideas are based on a new more accurate understanding of some fundamental aspects of this project. Basically lots of juicy info that should help give us a much better model for understanding why we get the results we do, what new ideas might be worth trying and what things we will not be able to 'fix'. It's a big document already, and it's not nearly finished yet, so you'll have to excuse me for not ruining it by giving away all the goodies in the thread I'm not sure If I will attempt to include sections explaining our existing knowledge:the various attributes of different types of circuitdifferent types of driverAGCother ways of approaching the task (like mechanical systain, umbilicals, ebow etc.)Problems like grunge, squeal, poor performance etc. what the causes might be and what solutions might existIf folks want that stuff, then I'll have a go. I imagine I'll be looking for somewhere to host it at some point in the near future - so any suggestions would be cool - somewhere thats free and where folks can leave comments and suggestions, so I can fix mistakes and add any suggested topics and ideas. cheers Col Link to comment Share on other sites More sharing options...
psw Posted February 11, 2008 Author Report Share Posted February 11, 2008 Just an addition... On the present setup, I altered the circuit with a 10Meg input resistor (input impedance). I also went back to a 500k volume pot on the guitar (not treble bleed cap or anything). One effect is that on the b string on the note D and others, you get a beautiful and strong harmonic after a very short while. turning down the volume control just a touch makes the same note ring at it's fundamental. Sustain is possible even with the volume turned down so I assume that it is wired "correctly" yet, the volume control pot seems to influence not only the volume but the response of the system, particularly in relation to harmonics in normal mode. In harmonic mode, I am getting very poor responses. Typically none (except on very low fretted tones) and the need for more power at that. There is noticeable squeal in some settings and distortions at greater gains, plus, turning down the volume of the guitar in harmonic mode (driver leads reversed) causes noise. There seems to be some correlation between the polarity of the pickup and the direction of the driver wires perhaps that also feeds in another level of complication into this idea about secondary coils and such; I feel very out of my depth in understanding what is going on but some of it certainly seems to be producing the right effect, while other less spectacular (like the harmonic mode). The interesting thing is that if these harmonics in normal mode could be enhanced, there is more potential and a better sound than the phase switch solution IMHO and on this guitar. There are harmonic "hot spots" that are in some part obviously related to frequency. On this the note d and a are a little more prone to harmonics...yet other responses are a little bit of a mystery...why for instance is the D string highly harmonic and the resulting harmonic two octaves above while the same notes on the g string produce a true fundamental...truly weird...hmmm pete Link to comment Share on other sites More sharing options...
psw Posted February 11, 2008 Author Report Share Posted February 11, 2008 further addition... I hooked up a 500k(Audio) pot to the unconnected neck pickup leads. At zero "volume" the same type of response as if open, but with the load, the harmonic resonances are smoothed out and so ring as fundamentals where these harmonics are more prevalent. There appears to be no change in driver efficiency by doing this, so still a good strong sustain as far as I can tell. Harmonic mode seems to work a little better...but still not great...certainly not the response that I get with the original sustain-o-strat. The drive response seems pretty good, I have a pretty high action on this guitar, am planning on lowering it a bit and the neck pickup/driver is staggered so that the b pole is significantly lower than others to the strings. Despite, or perhaps because of this, the b string has one of the strongest responses. Also, the ability to drive the strings this well with 10-46 gauge strings (what I prefer anyway) bodes well for the possibility of using lighter gauge strings for those that have requested this. I am getting perfect and equally powerful sustain on the high e as any other string, right up to the 22nd fret. In fact, the response seems pretty even regardless of the changes in action across the board and the staggered poles. One thing people should attend to is the adjustment of the pickups. The bridge pickup being as close as possible to the strings seems to not only improve drive and balance but significantly improves EMI reduction and rejection. The adjustment of the bridge pickup in this way is equal or possibly more important than the adjustment of the driver (which should also be reasonably close within the bounds of practicality (magnetic pull and the effect of the action). Some encouraging results and a new area for me to explore. Curtisa may wish to do parallel experiments with his guitar as it would seem that his system could easily be adapted by inserting a similar resistive load or pot in there. Good work... pete Link to comment Share on other sites More sharing options...
col Posted February 12, 2008 Report Share Posted February 12, 2008 I hooked up a 500k(Audio) pot to the unconnected neck pickup leads. At zero "volume" the same type of response as if open, but with the load, the harmonic resonances are smoothed out and so ring as fundamentals where these harmonics are more prevalent. There appears to be no change in driver efficiency by doing this, so still a good strong sustain as far as I can tell. Harmonic mode seems to work a little better...but still not great...certainly not the response that I get with the original sustain-o-strat. First guesses as to what might be happening. The parasitic pickup coil is using some of the energy that would otherwise be forming the drivers magnetic field. This is reducing the effective inductance of the driver(thats a big loose guess - real inductance measurements would be nice). If you stick a resistor between the ends of the pickup coil, you reduce the current induced in the coil... not sure if this means that it doesn't take as much energy from the driver or if it does but the energy gets sucked in by the resistor... either way you limit the magnetic field induced by the pickup. So the guess or really question is: does this change the inductance of the driver! If so it would also change the phase response, which would change the frequencies most likely to sustain well, and alter which ones will produce harmonics. Another possibility is that the driver inductance stays the same, but the damping effect of the pickups parasitic field is reduced. The pickup has a very different inductance (many more turns) and therefor phase response to that of the driver (it will damp some frequencies way more than others). So if its influence is reduced, the overall phase response of the two combined will change - causeing a change in which notes/harmonics work well etc. (that's all assuming that the pickup is damping rather than enhancing, but I think that's a pretty safe bet) It is important to note that a relatively small change in the phase response is all it would take to go from weak or non-existant 'full harmonic mode' to working OK 'full harmonic mode' ! ------------------------ I suppose another way to think about it is that the pickup coil isn't taking energy from the system... it's just part of the driver. the effective driving field is a combination of the pickup coils field and the driver coils field. Reducing the effect of the pickup will still change the phase response. We may also lose some energy as heat in the resistor, but maybe not enough to be noticable - particularly in a system with AGC. One thing that would be really useful is a dual channel scope. That way we could actually look at the phase difference by comparing the drive signal at the circuit with the pickups output signal... and see what difference these adjustments make at different note frequencies. damn, now I need a scope as well as an inductance meter. LOL cheers Col Link to comment Share on other sites More sharing options...
psw Posted February 12, 2008 Author Report Share Posted February 12, 2008 Yes...well I think you are on the right track there col...and on an old computer I think I had a dual software scope as freeware...there are a few things like that...but of course relies on the user somewhat.... Ok...so here is another thing...I tried a couple of different pots 500k and 1meg and 2 meg. All can replicate the shorted lead sound (ie no resistance) but the full range to full shorted isn't there. higher pot values get close and 500k is not to bad at it. What I did try is to short the leads with a capacitors from 0.01uF to 220uF...smaller is better. There is a "fizz" effect in high frequencies and drive levels (as you would expect, but at lower levels no fizz). This capacitor effectively stops the fizz. Also, there was a kind of ringing overtone behind the attack of notes at higher levels...this and/or a load removes that! I was hoping for some radical changes in harmonic response...there seems to be some...generally even a large load (closer to open) reduces the effect...although you get hints of some notes being more "harmonic" in response...hmmm Perhaps I should have the cap in series with the load rather across it...anyone got any other ideas to try? Still no real harmonic response (may actually be dampening) with the phase switch except on the low e string. What I need, or seem to be looking for is a variable phase pot...preferably passive....or perhaps something in the front of the amp.... pete Link to comment Share on other sites More sharing options...
col Posted February 12, 2008 Report Share Posted February 12, 2008 I was hoping for some radical changes in harmonic response...there seems to be some...generally even a large load (closer to open) reduces the effect...although you get hints of some notes being more "harmonic" in response...hmmm Perhaps I should have the cap in series with the load rather across it...anyone got any other ideas to try? I'm not sure that there will be a huge benefit to using this as a control - might be better to find the best resistor value, then use other techniques to actually control harmonic content. I imaging that you will enjoy some of the possibilities of the all-pass filter approach . Did you try the variable output cap thing that I described a few posts back? (in post #3485) That might give you some control over fundamentals vs harmonics. cheers Col Link to comment Share on other sites More sharing options...
psw Posted February 12, 2008 Author Report Share Posted February 12, 2008 Did you try the variable output cap thing that I described a few posts back? Not yet...to do this and other things I need to expanded my tightly compacted circuit so I have started building that. I am puttin DIL sockets where critical components are placed in order to make changing components easy (kind of half a breadboard...). I don't want to breadboard the circuit because me an breadboards seem not to get along somehow...always some noise or loose connection that is hard to diagnose and because it has to be tested in the guitar, is bound to get damaged...this is probably a better strategy. In doing so, I had to study the circuit a little closer and found some other possibilities. For instance...the inverted input (pin 2) and the ground (pin 4) are tied as is usual however, it may be advantageous to tie them via a capacitor, I notice some ruby mods at ROG suggest this as a means to "sound like a bassman or Hiwatt, etc"...I am thinking that this would cut some high frequencies and stop some of the fizzyness perhaps by canceling out some of this from pin 3 (the usual input). Also, I may find some changes in response with alterations to the input capacitor, presently 1uF so quite large. I need to get some kind of rotary switch I think to try out different caps...I am sure there will be some interesting variations, but I find it best to leave a mod in the guitar for a bit and playing with it a while before dismissing it or adopting it wholesale. I'm not sure that there will be a huge benefit to using this as a control - might be better to find the best resistor value, then use other techniques to actually control harmonic content. You are probably right, however it does make some drastic effects to efficiency and harmonic content as well as dramatically altering EMI and squeal thresholds. I think I will need to get some much bigger loads on there and try out some different capacitor configurations too. A small cap bridging the pickup wires with the load seems to make squeal disaper for instance and that annoying tinny fizzy sound that can occur at high gains...so if there is some distortion, it is at least not so "fizzy" and thus more musical. Another aspect is that it may well be the distortion of the amplifier running at higher gains that brings forth some of these harmonic effects. While this is risky as distortion can introduce unwanted "fizz" and EMI effects plus squeal sensitivity, the effect of these selectable harmonics that bloom rather than emerge from fundamental suppression is incredibly beautiful. The are much stronger and better controlled with less noise too, compared to the phase reverse strategy if you think about how that works... In the phase reverse strategy, the drivers action suppresses the fundamental and drives the upper harmonics left. It tends to be weaker as a result as it is subtractive. Further, once the harmonic is sounding, this too is being "picked up" and reversed and now the device is trying to suppress the harmonic it is playing too...well so it seems, especially on this guitar (unless I am missing something)??? Now, if the harmonic is produced by another means (say a square signal or actually plucking a harmonic) the driver is pushing this frequency and so drives equally as strong as if it were a fundamental note and there is no subtractive driving either, so the note blooms and increases in volume without struggling. Also, there is no weird delay between the fundmental and the harmonic...the transition is smooth and natural...where as, with the harmonic switch there is often a moment of silence when used during the sustain of a note as the fundamental note playing is suppressed and then the harmonic note kicks in. A neat trick that I used on the previous model was to use the harmonic switch to get the harmonic ringing then switch back to the fundamental mode to keep the harmonic ringing nicely. (sometimes you would get even a higher harmonic doing this too...so a lot of techniques to learn) One effect of this pickup open discovery is that I can get great sustain without maxing out the LM386...that means I am running a lot cleaner, the circuit doesn't even have any preamp gain...less EMI, fizz and range of gain effects plus bonus battery life! Also, likely to be able to drive even lighter strings...even sustainiac and co have problems with that. So far with this I am getting amazingly strong sustain on the higher strings, if anything the lower strings are struggling to sustain quite as well as on previous guitars without a bit of a boost. This, along with the increased clean headroom means that there is better polyphonic sustain too and the lower strings don't predominate so much, if at all within chords meaning you can sustain whole chords more easily, even produce harmonics within chords... As a side note...I have been using this a bit with a slide too and it is just fantastic for that. You can slide the harmonics all over and produce interesting effects with the glissando of the slide plus the polyphonic side of it is interesting with this too. On previous models, I have even had trouble getting a good slide response...this one is great (except for the lack of proper harmonic mode as such...though harmonics are possible). I imaging that you will enjoy some of the possibilities of the all-pass filter approach I don't know if I will be voyaging into this as I would need to redesign the circuit a little and I still have not got the switching thing under control yet. Even on this two pickup instrument the neck pickup is not actuall hooked into anything...just hanging there with a load attached to it! Also, being an electronics doofuss (as LK used to say privately to me), I am not sure that I have enough knowledge to effectively pull it off. The circuit I was looking at was described as a second order all-pass filter and used an instrumentation chip (interesting in itself as it contains 3 op-amps and similar single supply and pin layout as the LM386 (pins 1 & 8 control gain for instance) but a little hard to get and expensive). I also want to keep the circuit simple and small at this stage. I think there is still a fair amount of room for passive experimentation...the circuit uses a mosFET to buffer and operate the AGC so I don't have any op-amps in there really to co-opt for dual purposes. So for now, I still have a bit to play with in the existing component values (especially the output caps) and I'd really like to find a way of making a better control system with more variations than the simple harmonic switch. The simple act of discovering the practical differences between shorted and non-shorted pickup under the driver has been a revelation to me, though I still have not found a conclusive explanation of what is actually going on there...but it is enormously interesting. It is also a little worrying to my concept as obviously there will be enormous variations with different pickups (stacked, etc) below it, again straying from the universal circuit ideal....hmmmm later... pete Link to comment Share on other sites More sharing options...
col Posted February 12, 2008 Report Share Posted February 12, 2008 It is also a little worrying to my concept as obviously there will be enormous variations with different pickups (stacked, etc) below it, again straying from the universal circuit ideal....hmmmm Yes. And this is a similar variation to that which will occur just due to the inductance factor of the cores of different pickups as I was explaining a few posts ago. As I see it there are two(maybe 3) options for a ready to install piggyback system like yours. #1 work out a system that is a compromise between working similarly with different installs on the one hand, and having a less than stellar performance as a result, but needing no edjustment. (pretty much what Fernandez et al have done - and they don't have to worry about piggybacking). #2 learning and understanding about the impact of inductance and phase on the system, then providing a unit that can be adjusted to match a wide range of pickups - this will need to include some way of measuring the inductance either directly, or indirectly (by indirectly I mean some tuning method where you can for example listen for some characteristic noise from part of the circuit while tuning - or something like that) #3 (a big old maybe) A digital system that can tune itself in - with a learn mode, it can calculate the required phase offsets and memorize settings for the instrument it is installed on. I'm sure this is possible, unfortunately, the circuitry and software will both be high tech. We're talking about a DSP processing unit (possibly alongside a general purpose cpu) - you would need to do some studying before even considering this approach - it's not something that can work through trial and error. It may be possible to get some sort of specialized DSP oriented PIC thats ready to go, in which case all you would need is some simple support circuitry... but of course it will be hard to avoid having to write your own software. Personally my favorite is #2 (I love the idea of #3, but I'm not sure it will work any better, and its certainly not such a good DIY option). The thing with #2 is that it can still work with peoples DIY drivers, or with other forms of ready supplied drivers. So someone going for a stand alone driver (say they only use a bridge humbucker anyway) can use the tuning method and therefor the circuit needs no modification to work just as well on that installation... cheers Col Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 12, 2008 Report Share Posted February 12, 2008 Hi diy-comrades, I've more or less read the thread and just have built my second driver. I took your advice and used 0.2 mm copper wire. It's a humbucker with 2 blades. Dimensions: 1.4 x 16 x 57 mm. Coil height: 5 mm Windings: 2 x 60 turns Resistance: 8,4 Ohms My first driver was a single coil design and terribly sensitive to magnetic feedback (pigscreamer). The new driver seems to be able to do the job. I get string feedback without squeal. I've only done some outboard testing with the new one, but I have good hope it will work when it's properly installed. Col you seem to want a more systematic, scientific approach Electrical properties of the sustainer/driver There is an easy way to measure the inductance of the driver. You need (1) a sine wave generator with a low impedance output (mine is 50 ohms) and a constant voltage output level over it's frequency range (2) an oscilloscope (3) a multimeter that measures frequency. My oscilloscope is a very old handyprobe 1, so nothing special. This setup also comes of handy when biasing a fet or setting up voltage levels needed for your opamp(s). Create a notch filter. For that purpose I connect in series: 180 ohms resistor, 680 nFarad capacitor and the driver. Connect this chain to the sine wave generator: resistor to signal, unused driver connection to earth. Now probe the signal in between resistor and capacitor. Now you need to walk through the frequencies to find the resonance frequency where the voltage drops the most. Then measure the frequency (signal of sine wave generator, not in between resistor and capacitor where because of the voltage drop the measuring can be problematic). Calculate inductance L = 1/(4* pi^2 * F_resonance^2 * C) In my case it measured 6000 Hz: L = 1/(4* pi^2 * 6000^2 * 680e-9 ) = 0,001 H = 1 mHenry The highest fundamental is about 1100 Hz. X_C = 2 * pi * f * L = 2 * pi * 1100* 0,001 = 6,9 Ohm Now we know the impedance at 1100 Hz. Real component R = 8,4 ohm, imaginary component X_L = 6,9 ohm Z_1100Hz = (8,4 ^2 + 6,9 ^2 ) ^0,5 = 10,9 ohm There are 2 reasons why at 1100 Hz the driver works less efficiently: (1) higher resistance (10,9 instead of 8,4), lower current (I = V / Z), lower magnetic flux (2) phase shift between voltage and current arctan(X_L/R)= arctan(6,9/8,4) = 39,4 degrees (0 is in phase, 180 is out of phase) Note that 90 degrees is the maximum phaseshift. At 90 degrees phase shift it's all conductance, the driver works as an ideal conductor. The driver won't dissipate energy, it stores energy and then spits it back at the lm386 (in case of the f/r. Therefore a zobel network is used to keep the impedance low at high frequencies and prevent instability. The following is my DIY-theory. Maybe it's incorrect and completely useless, but my goal is to produce some kind of benchmark for drivers so we can compare one driver to another. Maybe there are better ways to express the quality of the driver. As long as there is a way of measuring it, otherwise i don't believe it. It would be nice if I could combine (1) and (2) in one single number, a compensation factor for high frequencies. I will use the term specificaly for 1100 hz. (1) 8,4 / 10,9 = 0,77 (2) use cosinus function normaly used for calculation of power: P = I * V * cos(phase shift between I and V) In order for the sustainer to work the string should be helped. So when the string moves down the driver should pull and when the string goes up the driver should push. Just like a swing the timing when to push and when to pull is important. Phase shift, pushing too late or too soon, reduces efficiency. cos(39,4 degrees)=0,77 (!) (1) and (2) are the same. So the compensation factor should be 0,77^2 = 0,60. If there is a linear relation between current and magnetic flux then we could use this factor instead of phase shift and impedances. The magnetic flux at 1100 hz is 0,60 times the magnetic flux at let's say 50 hz. So in order to get an even response the questions are: (1) is a compensation factor of 0,60 enough? (2) can we construct drivers with a higher compensationfactor (closer to 1). Maybe some of you have constructed a much more efficient driver, I only know what I have. If this compensation says something essential about the driver's quality maybe we can draw conclusions about the rest of the circuitry. If the driver doesn't get a good benchmark but is sustaining flawlessly then the circuitry must somehow have compensated the driver's weaknesses (eq, more power, agc). And if a good driver doesn't sustain, we should suspect the circuitry and try to improve it. Sorry for being long-winded, it must be the thread that makes me do it. Also, this contribution of mine seems to be a bit out of sync with what is being discussed at the moment. But it would be nice if every s******er builder has a way way to measure and calculate the inductance of his driver. Even more so if he shares his results with the other builders. Link to comment Share on other sites More sharing options...
psw Posted February 12, 2008 Author Report Share Posted February 12, 2008 Some interesting things there, but most likely beyond my capabilities...I used to get PLL chips and stuff, but I have to acknowledge my limitations and go for simple and workable. I have had these things working on many different guitars and each does have it's own character for sure...but mostly they have worked in a usable fashion. Check out some of the patents, I am sure there are a few that describe the variable phase to frequency techniques they use to provide better phase response. If you had an exact phase, the system would be incredibly efficient requiring little power to keep the strings humming (although I am not sure how it can cope effectively with multiple strings with a single driver in relation to phase). This is of course what I have tried to address by efficient driver "fast" design, and continue to pursue this line of making the driver efficient enough to avoid the phase compensation requirement. The position of the driver relative to the bridge pickup too must have some effect I would presume and would need to be factored in, something I am not sure that commecial systems really compensate for and I suspect that the phase side of things is ok, but still a comprimise in order to get better high string response. Another factor that might effect phase is the simple relative heights of the driver and pickup to the strings....perhaps the distance between driver and strings, which does need to be adjusted to get a really good response, plays a role in phase ratios. ----------------- I am not sure of the inductance factor as I have tried this on a few pickups, but this is an interesting thing you are proposing. If inductance really is a big factor, and it would seem from this guitar that the shorting and non-shorting of the pickup coil under the driver, does have a dramatic effect on something and is adjustable with a load, then the pickup/driver combo appears to have an additional feature that may be put to good use. Perhaps this coil effects inductance...if so, then built in is an adjustment method and so opens up an easily adjustable (compared to adding or subtracting core material) driver inductance. Your comments have given me an idea...perhaps a diode (or two end-to-end), similar to the way my AGC works could be used to keep the coil open but when internal power in the coil rises above the breakover point, it will conduct shorting the coil. This could be made more sophisticated with a filter cap to short high frequencies through the coil and so suppressing noise and fizz and high frequency noise artifacts (perhaps created by static forces or general noise in the signal system) too. This could be adjustable by altering the breakover point with a variable resistor. Additionally....I have not had time yet to try mega-loads. The highest tried so far in a variable resistor is 2meg...perhaps it needs still more (10meg plus) to get any radical changes, though 2meg approaches the response of an open coil. Bear in mind that with an open coil and lowish power, I was getting sparks out of the thing!!! Also...perhaps inductance does alter phase and so an adjustable inductance system may allow a novel way to adjust this aspect at the same time...without resorting to CPU digital control. -------------------- Ahhh...and when posting this, I see a new contributor....WELCOME Fresh Fizz... Sorry for being long-winded, it must be the thread that makes me do it. Also, this contribution of mine seems to be a bit out of sync with what is being discussed at the moment. But it would be nice if every s******er builder has a way way to measure and calculate the inductance of his driver. Even more so if he shares his results with the other builders. Ahhh...it does seem to have that effect. Most people do contribute...often it is only after they have succeeded or failed on their own (as it would appear that you have also). I like the deletion of the s*** word...I wish I could keep up that habit. It is a problem as even as you described the measuring of a driver involves both mathematics and equipment that many don't have. So it would be nice if those who can, do make measurements, but those who cant will still be left out as they wont know what they have to compare it to others...if that makes sense. My approach has been to try and work towards guidelines that appear from experience to provide the right qualities for what we want. One thing to consider is if we were to make a final statement on a standard circuit design. This is the most commonest of questions. My feeling is that a simple amplifier with perhaps no preamp gain but with precautions such as the zobel and other means be used. To that end, the basic ruby seems to be appropriate with it's jFET buffer. Do other's have thoughts on this? At least if people come across particularly good performances and the same circuit is used, then they could be compared, give people a definitive answer and starting point for circuit design and allow direct comparisons. In my work, I have always tried to shy away from complex circuitry solutions, partly due to my own limitations, and partly because compensation tends to take the pressure from the driver design efficiency where I think the present compensation methods are a compromise anyway and that an efficient driver, even if you need to look into compensation circuits, will require less if any compensation for a similar performance...but then I am biased!! Note that 90 degrees is the maximum phaseshift. At 90 degrees phase shift it's all conductance, the driver works as an ideal conductor. The driver won't dissipate energy, it stores energy and then spits it back at the lm386 (in case of the f/r. Therefore a zobel network is used to keep the impedance low at high frequencies and prevent instability. This is an important point that needs further elucidation and investigation. perhaps some of the energy in the secondary coil effect is from such things, or compensates for them...perhaps...ok, I am out of my depth here...must be the mathematics... +1 contribution and don't worry about interrupting a conversation....perhaps we do need to step away from things we (of most I) don't fully understand, and everything brings up new thoughts or focuses the attention back onto details we should have completed (like a basic circuit design!) a fair way back. later... pete Link to comment Share on other sites More sharing options...
utopian isotope Posted February 12, 2008 Report Share Posted February 12, 2008 (edited) Anyone here that has tested/experienced NE571(SA571) as compressor/limiter? Off-topic this might be, but after reading about that AGC-stuff here, I searched my components, and found some NE571's. It is some kind of compressor/expander(compander) chip. Originally one of those was used in Craig Anderton's "Roctave Divider", that I built years ago. It seems to be quite rare chip, since I haven't found much information about how to use it as a compressor and/or limiter. -------------------------------- @psw: I'm just curious about that PLL. I assume you mean 4046 or similar? How did you use it, if I may ask? interesting subject it is (atleast for me), because I (ab)used that chip on some of my testings in the past. Edited February 12, 2008 by utopian isotope Link to comment Share on other sites More sharing options...
col Posted February 12, 2008 Report Share Posted February 12, 2008 (edited) Hi diy-comrades, I've more or less read the thread and just have built my second driver. I took your advice and used 0.2 mm copper wire. It's a humbucker with 2 blades. Dimensions: 1.4 x 16 x 57 mm. Coil height: 5 mm Windings: 2 x 60 turns Resistance: 8,4 Ohms My first driver was a single coil design and terribly sensitive to magnetic feedback (pigscreamer). The new driver seems to be able to do the job. I get string feedback without squeal. I've only done some outboard testing with the new one, but I have good hope it will work when it's properly installed. Col you seem to want a more systematic, scientific approach Yes, and it's great to see someone willing to join me on that road at last Electrical properties of the sustainer/driver There is an easy way to measure the inductance of the driver.... Wow, that seems like an interesting approach, but there are certainly simpler ones that use less equipment - What I'm really looking for is a way that folks can take these measurements without needing access to oscilloscopes, inductance meters or 'real' signal generators. I was hoping to get some method worked out using a DMM, a PC soundcard as generator, and some simple to build DIY circuitry. I have discovered a couple of approaches online, but unfortunately, I don't have an inductance meter yet to verify any results... and I've also discovered that there are LCR meters available on ebay with 'buy it now' prices as low as £10, so maybe the whole discussion is moot ? L = 1/(4* pi^2 * 6000^2 * 680e-9 ) = 0,001 H = 1 mHenry hehe that is interesting, a few days ago I worked out a ball park figure for inductance by scaling the specs I found online for fender strat pickups - guess what the resulting estimate was... yep, 1 mHenry !! (pickup specs) inductance 2.2H to 2.8H so roughly 2.5H turns 7650 (up to 8350) so lets say 8000 resistance 5.88k so if we assume a roughly similar core factor, we can extrapolate some ballpark figure for a sustainer drivers inductance. awg 42 is 0.0025 in diameter (0.0025 what though? inches) 0.063mm Rm = reluctance, N is num turns, L is inductance from pickup Rm = N^2 / L = 8000^2 / 2.5 = 25600000 to driver L = N^2 / Rm = 150^2 / 25600000 = 0.00088 = 880uH or very roughly, 1 mili Henry (I’m assuming our rail cores will have a little more inductance factor than a strat pickup) The highest fundamental is about 1100 Hz. X_C = 2 * pi * f * L = 2 * pi * 1100* 0,001 = 6,9 Ohm Now we know the impedance at 1100 Hz. Real component R = 8,4 ohm, imaginary component X_L = 6,9 ohm Z_1100Hz = (8,4 ^2 + 6,9 ^2 ) ^0,5 = 10,9 ohm There are 2 reasons why at 1100 Hz the driver works less efficiently: (1) higher resistance (10,9 instead of 8,4), lower current (I = V / Z), lower magnetic flux (2) phase shift between voltage and current arctan(X_L/R)= arctan(6,9/8,4) = 39,4 degrees (0 is in phase, 180 is out of phase) Note that 90 degrees is the maximum phaseshift. At 90 degrees phase shift it's all conductance, the driver works as an ideal conductor. The driver won't dissipate energy, it stores energy and then spits it back at the lm386 (in case of the f/r. Do you mean that 90º is the largest phase difference that won't cause losses, or that its actually more efficient than no phase difference ? It would be nice if I could combine (1) and (2) in one single number, a compensation factor for high frequencies. I will use the term specificaly for 1100 hz. (1) 8,4 / 10,9 = 0,77 That help us compare two drivers for phase distortion, but it doesn't help so much in working out how to tweak the rest of the system to get the optimum performance from any single driver. It also only takes into account the losses due to phase distortion. What about the fact that we can get a stronger electro-magnet from the same current by using more turns of thicker wire... with the side effect that there is a bigger variation in phase with frequency over the guitars range... where is the 'sweet spot' after we have factored in the phase shifts of the circuit, the pickup, the mechanical aspects of the system and created a zobel network that provides the best possible 'correction' ? It's possible that the optimum driver might not score very well using your metric? (2) use cosinus function normaly used for calculation of power: P = I * V * cos(phase shift between I and V) Surely using that formula, P = 0 when phase shift is 90º... what am I missing? In order for the sustainer to work the string should be helped. So when the string moves down the driver should pull and when the string goes up the driver should push. Just like a swing the timing when to push and when to pull is important. Phase shift, pushing too late or too soon, reduces efficiency. Yes. However, this is true for the system as a whole rather than for the driver in isolation. The driver will have some sort of non-flat phase response(Pete seems to have minimized this through experimentation by making the impedance mostly resistive over the guitars frequency range, but possibly with other negative side effects). The circuit too is unlikely to have a flat phase response, tweaking of output cap, zobel, and other components will change its phase footprint. Theres more, the pickup that our signal comes from will surely a pretty hefty impact on the systems 'phase sum' as well!... And there even more (pheck me this is getting ridiculous)... there is a physical phase issue to factor in along with all that other stuff: (time to spill some of the beans me thinks - nobody seems interested in a more complete document anyway). Ok, this may or may not be news to you guys - it was to me, kinda anyway. Using standing waves as a model for understanding how the string vibrates is woefully inadequate for us if we want to fully understand this project and build the best DIY sustainer possible. What really happens in a vibrating guitar string is quite different (it's very similar to what is happening in a violin string) What I am talking about is something called 'Helmholtz motion'. Theres a good animation of how it happens on a bowed string here. What is even more interesting for us is that it also happens on a guitar - when you pluck a string, a kink in the string (Helmholtz corner' moves down the string on one side, reflects off the fret or bridge then returns along the other side (For a plucked string, its not exactly the same as Helmholtz motion - there are two kinks moving in opposite directions from the pluck - but for our purposes its effectively the same).... If you don't believe this nonsense, take a very close look at this amazing video clip of Helmholtz motion actually happening on a guitar! So why is this so critical for us ? Well, its to do with the gap between the driver and pickup (something Pete's had a hunch about for some time). If the signal from the driver is exactly in phase with the signal from the pickup, there is a section of the kinks journey around the string where the driver will be 'pushing' the wrong way. As the kink passes the driver moving towards the bridge, the section of string between kink and bridge is still moving 'up' while the section between kink and fret/nut is now moving 'down'. The pickup is collecting the signal from the portion moving in one direction while driver is trying to apply that signal - with force - to a section of string that is now moving in the opposite direction... oops... some hefty damping is occuring at this time! (Whats more, this damping is happening exactly at the time when it is most important to have optimum drive if you want that full rich sound we've been discussing recently - more about that another time if you're interested...) Unfortunately, the perfect phase offset required to prevent all damping due to this effect will be different depending on which note you are playing at which fret. e.g. an E played on the open 1st string will have a kink moving twice the speed of the kink in the same note played on the 6th string 12th fret. The phase offset required to 'fix' the 6th string note would be twice that required for the 1st string! Of course, the scale length of the guitar also has some impact here. I think it will be possible using carefully designed circuit and driver along with some basic phase tweaking circuitry to get at least a 'best fit' compromise that gives a more efficient better sounding system and an understanding of what the tolerances are for the sytems components... I figure that at least to start with, we should be looking at just the high E string and optimizing for that. Then its open to anyone who wants to to try and tweak things to suit the lower strings - hilbert transformer or some such... I don't think we need to worry about the 'same note lower string higher fret' thing - just optimize for each note being played on the highest string that it is available on. (I also wonder if we[me anyway] have been confusing ourselves by using the term 'phase' in to related but different ways, but interchanging the two due to ignorance ? is the 'phase' offset of the drive signal the same as the phase offset between voltage and current as described by Fresh Fizz?, or are they closely related but subtly different concepts ?) (2) can we construct drivers with a higher compensationfactor (closer to 1). Maybe some of you have constructed a much more efficient driver, I only know what I have. Surely a driver using fewer turns of much thinner wire will have a compensation factor closer to 1? As the wire gets thinner and we reduce the number of turns, the reactive component of the impedance moves towards zero and the compensation factor moves towards one... unfortunately the drive is also reduced in this case, so efficiency is way lower. what we need is a compromise between linear phase(of the whole system pickup, circuit, driver & guitar) and maximum drive - over the guitars frequency spectrum... personally I feel that this will involve more turns of thicker wire and some compensation circuitry to deal with the phase response and the 'Helmholtz Gap'. Maybe its time to have another look at an old idea in the light of new understanding... I suggested many moons ago having a dual driver with the equivalent of a woofer and a tweater, one section optimized to handle high frequencies, and the other for low frequencies.... this could maybe be in the same format as existing dual core setups, but with parallel coils of different specifications.... we'd probably need annoying extras like a crossover to make the most of it, but its worth consideration. Sorry for being long-winded, it must be the thread that makes me do it. Also, this contribution of mine seems to be a bit out of sync with what is being discussed at the moment. But it would be nice if every s******er builder has a way way to measure and calculate the inductance of his driver. Even more so if he shares his results with the other builders. Don't apologize - You sound like exactly the sort of windbag we need around here and definitely not out of sync either, I needed a push to start airing some of my new discoveries... maybe more will follow soon - who knows. cheers Col Edited February 12, 2008 by col Link to comment Share on other sites More sharing options...
psw Posted February 13, 2008 Author Report Share Posted February 13, 2008 Nice reply and some nice new perspectives...not sure if I am fully convinced of the direction, in particular to complicating it further, but it also elucidates the many, many fascinating areas the project touches on and how it forces some consideration of some very interesting fundamentals. I was interested to see that animation and a little surprised....this is the kind of thing I was trying to say by suggesting that simply plucking the string causes "distortion" a little while back. Picking angle and strength offers a huge range of sounds, should we not be surprised that when we electromagnetically excite a string, either from nothing or from plucking, that it might sound a little "different"? Using standing waves as a model for understanding how the string vibrates is woefully inadequate for us if we want to fully understand this project and build the best DIY sustainer possible. What really happens in a vibrating guitar string is quite different (it's very similar to what is happening in a violin string) A fascination animation there...so, if we were to assume no plucking and excitation only by the driver, could we expect a more violin bow kind of effect emanating from the location of the driver? I see some signs that eventually, we may be getting closer together on many issues, or that some areas I had previously explored and now put aside, are being considered wider. However, I have not yet been convinced that they are areas of productive pursuit...but we will see! Surely a driver using fewer turns of much thinner wire will have a compensation factor closer to 1?...having a dual driver with the equivalent of a woofer and a tweeter, one section optimized to handle high frequencies, and the other for low frequencies.... These were two fundamentals amongst many that informed the HEX designs. A driver for each string and a radical driver elements and magnet arrangement. Others included heat-sinking (important if thin wire coils were to be considered) that incorporated ferrous epoxy to help magnetically shield it in an exoskeleton, and a radically different orientation that sought to move the strings from side to side rather than up and down and also direct any stray EMI more towards the sides of the strings than along it to the pickups. There were more too...if I could recall...and I spent a year in this pursuit. One thing that I'd have always hoped to do was to drive the strings from the bridge end of the string. Experiments showed that this was possible but the location of most bridge pickups did/does seem far to close. This also had a side benefit of using the metal in the bridge too to absorb stray EMI or become a part of the driver structure itself. Recent experiments with the bass driver where the pickup is far from the bridge indicate that this is a preferable location for the driver, but other than on a variax like instrument without magnetic pickups....probably not a likely innovation on conventional electric guitars. After much experimentation into radical and very difficult to construct novel designs that tried to encapsulate these many factors and strategies, in the end...and it seemed particularly evident in the patents once I had done some work in the area...that it was a project of compromise. How many of these factors really matter...and what ultimate response are we seeking? Certainly, I believe that a lot can be, and has been done, to the design of electromagnetic string driving devices. I have consistently pointed out that this need not be seen simply a device for creating infinite sustain. If it were a device that only created harmonic responses it would still be a worthy pursuit. Hence the rejection of the s********r word. Yet there probably are limits to this too. I have thrown my lot in refining the very basic approach that I have found to have worked. While simple in concept, the idea of the thin coil was a direct result of miniaturizing drivers so that I could fit 6 tiny drivers between the strings in the HEX model...an important strategy left out of the previous list, that small in size means less EMI dispersal to the sides...or at least that is my half baked intuitive theory. I never did use the PLL chip, but the intention was to address phase discrepancies. I hope that I have addressed this "enough" for now in the driver design. Once we have developed a system that works well enough, then it opens the door for other areas of exploration such as what I am trying to move towards in my simple way, to bring out even more potentials besides infinite sustain and very basic phase reversal. A very important part is the whole installation issue. In truth, a single pickup guitar with all the sustainer can add to it, is more than generous. However, most applications will be in existing multi-pickup guitars. Installation provides many challenges and the details are enormously important to performance...the closeness of the strings to a pickup or driver, the effect of action, the distance between driver and pickup, the resonant qualities of the guitar and the resonances within a pickup that feeds the circuit. Many of these will vary from guitar to guitar but are fixed. More important is a practical approach to incorporating the device into a guitar electronically IMHO. The whole topic is mute until it is in a working instrument. Nothing else will have as much impact on development as people actually using and tackling with real wood, wire and magnets. Any design, no matter how well it works, will be called upon to do more, and exploit it's tantalizing features more, if it is being actively used. I really hope that I will be able to show how far the technology I am presently tinkering with, and the previous DIY version design on which it is based, has come with very simple technology. When it is working right, it truly is impressive, but also holds so many secrets and potentials. The development of the thing also opens a door to fundamental qualities of electric guitar physics and design. Anyway...enough from me...yes this thread is long, and so are the posts, but it is an indication of the enthusiasm of those participating at over 147,000 visits, obviously followed by many. Many have come and gone over the years...even I took a fairly long period of absence, yet still the enthusiasm and debate continued. Every time things quieten down, new members appear and every time I think we have a handle on things, some new and exciting further information or direction is brought forward. I would encourage people to actually build one of these in a basic format, or just go play a sustainer guitar a little to get a feel for what lies within this project...well done for following thus far and to all those who continue to breath new life into it...thanks pete Link to comment Share on other sites More sharing options...
col Posted February 13, 2008 Report Share Posted February 13, 2008 Using standing waves as a model for understanding how the string vibrates is woefully inadequate for us if we want to fully understand this project and build the best DIY sustainer possible. What really happens in a vibrating guitar string is quite different (it's very similar to what is happening in a violin string) A fascination animation there...so, if we were to assume no plucking and excitation only by the driver, could we expect a more violin bow kind of effect emanating from the location of the driver? No. there is no 'stick' or 'slip' effect, the dynamics are quite different. The point is that the vibration of a guitar string - when it is sounding like a guitar string - has much more in common with this model than with the 'standing waves' model, and that we need to rethink some of our assumptions in the light of this. It has nothing to do with sounding like a violin, (not a goal of mine anyway...) I want it to sound more like a guitar, and this is IMO a crucial part of the puzzle. It might help us find a solution, alternatively it might help us prove that there is no solution - either way, we are better off knowing. Surely a driver using fewer turns of much thinner wire will have a compensation factor closer to 1?...having a dual driver with the equivalent of a woofer and a tweeter, one section optimized to handle high frequencies, and the other for low frequencies.... These were two fundamentals amongst many that informed the HEX designs. A driver for each string and a radical driver elements and magnet arrangement..................................................................... ................ I'm guessing you misunderstood the bit about "a driver using fewer turns of much thinner wire will have a compensation factor closer to 1"? This was intended to support my suggestion that the 'compensation factor' metric is flawed (although we definitely need to think along those lines). Not that it proves fewer turns of thinner wire is intrinsically better... If you take that idea to its logical conclusion you see that it implies an 8 ohm single turn of superfine wire would be the ultimate driver - which is obviously bogus Anybody here know anything about Hilbert Transformers ? cheers Col Link to comment Share on other sites More sharing options...
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