col Posted March 22, 2009 Report Share Posted March 22, 2009 Hi Pete. You just had to make me lug my guitar up from the garage didn't you? In defense of the tiny strong magnets AL Would it be possible to make a short clip of just the guitar and sustainer through a clean amp with no effects (even better through a DI box to avoid room reverb and amp warmth). That way we can get a better idea of what's making the noises. You definitely have something happening, but it sounds like it's going to take some work to get it under control. There's a lot of fizz (our term) and grunge(sustainiacs term) in there for sure. There are lots of things that can cause this. The main problem is that there are different ways in which the drive signal can get mangled and get to the pickup. In order to keep everything sounding nice, there are two strategies we can use (there may be others, but these two both work). #1 keep the drive signal the same as the pickup signal - if we can prevent distortion getting into the drive signal, then if it bleeds through to the pickup, its not possible to tell it from the pickup signal. It is effectively masked -- Turn the gain down as much as possible; use a higher supply voltage for more headroom; use AGC/limiting/compression; filter out higher frequencies as much as possible within the circuit; avoid cheapo unregulated power supplies... #2 reduce the channels for drive signal to reach the pickup - careful design of driver; dual core drivers; humbucking pickups; tightly focussed fields; shielding and fancy wire; keep as much distance as possible between driver and pickup; thoughtful positioning of circuitry; high quality constuction throughout; fancy **** like isolation transformers; avoiding magnetic pickups... #1 is by far the most important in my experience, but as many things from #2 as possible will also help a great deal. if Pete is right and you are using long runs of wire, particularly if they are from circuit to driver, it would be worth making up some inter-8 weave wire - this limits the EMI from the wire. Its actually pretty easy to make this stuff I've posted about it before. just search the thread (botttom left of page) for inter-8 weave and check a few of the posts, there a pic of my very own wire, and some diagrams of how its woven. keep working on it - you're getting there. cheers Col Link to comment Share on other sites More sharing options...
al s. Posted March 23, 2009 Report Share Posted March 23, 2009 I don't know guys. Sounds like feedback to me Looks like feedback too... I see the strings moving. Even feels like feedback... I can brush the string into a new harmonic, or stop the sound by damping the string. . Maybe someone could post a clip of some "real" feedback. By the way... it will sustain until next tuesday..... You will have to trust me on that. A couple of corrections. The driver is mounted in the same position as Pete's Tele. That clip is two drivers side-by-side simulating a dual-rail driver. But I get a similar effect from the single pole driver The neck pickup is totally disconnected on this clip. I don't know about "fizz" Everything is perfectly silent at full power with the strings damped. You can hear fizz when the amp is cranking? The driver amp is 7watts. But it is also 3 watts, 1/10th watt and everything in between.. it has a volume knob. I'm sure the sound on the clip is not everyone's cup of tea. I am very happy with it. I'm sure its obtainable with Pete's driver. The physics are exactly the same. I get the feeling you are searching to to explain something that has a very simple explanation . a more powerful amp. AL Link to comment Share on other sites More sharing options...
psw Posted March 23, 2009 Author Report Share Posted March 23, 2009 I'm sure the sound on the clip is not everyone's cup of tea. I am very happy with it. And that's the main thing...it is still a musically viable sound and an alternative perhaps. I'd be happy to put up a demo of the tele...open offer to have me play a note or whatever to demo anything...I seem to be able to record direct to audacity with the amp now with relative ease. Otherwise, Al has made some extremely well made drivers, driver building techniques, a remarkable housing for the amp like a stomp box and a very neat circuit and I commend him on his efforts and progress so far, and his willingness to venture into lesser explored areas of the project. Just repeating my previous comments, this is what you should take away from them and so worth repeating. Perhaps when things settle down a little on the domestic front, I will venture into some recording and feature it a bit more. ... Meanwhile...I am considering doing a "build" for this Corvus thingy that would feature the sustainer and have a bunch of ideas...any creative souls who would like to encourage or assist in the technicalities might like to contact me. Looking at making a very stripped down but quite a radical thing, but may need help to work out things like the bridge and tuner construction and some of the look of the thing...if I in fact do it Entries close june 1st but want to keep anything under wraps initially from the general forum. ... pete Link to comment Share on other sites More sharing options...
col Posted March 23, 2009 Report Share Posted March 23, 2009 (edited) I don't know guys. Sounds like feedback to me Looks like feedback too... I see the strings moving. Even feels like feedback... I can brush the string into a new harmonic, or stop the sound by damping the string. Nobody is denying that it is feedback. However, the sound is nasty (but not in a good way), IMO. You have lots of feedback - its not all what I would call 'musical' feedback though. If that's just the sound of your guitar, then the problem doesn't lie with the sustainer, but you should get the rest of your kit tested. If you can't hear the grit and atonal ugly fizz in there, then you really should go to the doctor and arrange to get your ears tested (that's not a joke BTW, hearing damage is common amongst guitarists, and its the higher frequencies that go first). To me it sounds like the natural sound of the guitar is being choked. Most of the discussion and hard work on this project has been getting it from something like what you have - strong sustain with a LOT of artifacts, background noise and 'wolf tones' - to a clear strong even sustain that doesn't change the natural tone of the instrument. If you don't want that and are happy to have all the nasty background junk killing your tone, then that great, you won't have to go through the rest of the process. Its definitely a good start though, well done. Col Edited March 23, 2009 by col Link to comment Share on other sites More sharing options...
Donovan Posted March 24, 2009 Report Share Posted March 24, 2009 Just checking in. I've stopped work on this project as I need a GOOD driver and I don't think my attempts have been there as of yet. I've used up my stock of spare pickups. No data, but something tells me that the extra pole magnet that sticks out from the used up 3mmm of the bobbing adversely effects the sustainer... any ideas? I have read here numerous times about not attempting to cut down neodymium mags, but what about ceramics? Can one safely file thsese down? I feel I need to make a bobbin from scratch, which IMO is a larger undertaking. I want to try and take advantage of multiple designs by making a dual coil thin design. I have my pals at work keeping their eyes out for scrap material for me to play with and until then, it's playing with circuits for now. Recently built and installed a 9v LED clipper fuzz on my guinea pig strat... not a permanent mod, more of an exercise in learning how to work with op amps more efficiently. Anyway, some cool posts as of late. Can't wait to see what comes of the things being discussed recently... Col's current mode 386 and hank's hex work. Keep it up gents... and pete, should you need an extra few bucks, would love to purchase a coil from you. Link to comment Share on other sites More sharing options...
psw Posted March 24, 2009 Author Report Share Posted March 24, 2009 I think col can speak more about the dual coil designs than I can. It should be noted that col's current driver is effectively a dual coil pickup with thin coils about the size of an HB and the newer proposal driven by a current mode amp is in fact made from a full sized HB with many more turns and full thickness coils (as described in a recent post). Dual coils are working like a reverse HB pickup...the improved EMI is from the generation of equal but opposing magnetic signals but with reversed magnets. The down side is that typically, these signals are most attracted to their opposing poles as much as the strings...whereas a typical SC design throws the signal up and around to reach the reverse side and opposite pole of the driver....i.e. projection. This kind of thing needs to be considered in such designs, moving the dual coils apart (as col was eluding to previously) may create more of an arch and improve projection while a compact rail like design like I tried, may have very little projection requiring it to be placed very close to the strings. The bilateral design like sustainiac uses addresses this a bit and is worth considering in this context. It is something that may well affect Hex design also, many of mine had alternating polarities. Generally, having the coil as close to the strings seems to help a lot...I did hypotheses about whether the coil being on the edge of the magnetic field has some effect, but I have made coils with protruding poles that work. Single coil designs tend to have a fair amount of projection though compared to dual coil devices so this may be something to consider more with such a design. Cutting magnets can always be tricky. Typically ceramic pickups have metal poles which could be filled down. Alnico too can be shaped (although there are dangers with magnetized fragments)...the main risk is that heat (from grinding and cutting) and other factors seriously effect the magnetism and generally they will need to be re-magnetized. Ceramics are extremely difficult to shape and pose much higher risks...the material is generally extremely resistant to shaping and cracks very easily. Much better to find or adapt made magnets, combining multiple magnets or attaching magnetic materials to size. I do need some extra bucks...unfortunately, I received another phone call yesterday with a view to sell the house I am living in...this may make for a radical change in circumstances and perhaps even a halt to any construction and a loss of internet access as well. While things are so "unstable" it would not be wise for me to embark on promises that I couldn't keep. Typically, the time and effort to had craft such things outstrips the preparedness of people to pay for the work. Making them yourself can be very inexpensive but even with a coil made by me, the effectiveness of it may well rely on how it is put to use, the circuit and the installation...things outside of my control. But perhaps if things settle down, I don't have to move, I can get some employment, this divorce is finalized, and I can get over the loss of both of my children and pull myself out of this funk I'm in...I may well get interested in building these kinds of things again. Anyway...yes some interesting work going on, perhaps my efforts will be surpassed by such activites and who knows, perhaps I will be involved with other activities and projects. I had for some time being messing with piezos and such... pete Link to comment Share on other sites More sharing options...
col Posted March 24, 2009 Report Share Posted March 24, 2009 No data, but something tells me that the extra pole magnet that sticks out from the used up 3mmm of the bobbing adversely effects the sustainer... any ideas? I didn't understand that, can you try and explain again ? I have read here numerous times about not attempting to cut down neodymium mags, but what about ceramics? Can one safely file thsese down? I feel I need to make a bobbin from scratch, which IMO is a larger undertaking. cutting any permanent magnet will have an adverse effect on the magnetic field. Afaik in industry, the raw stuff is sold un-magnetised so it can be cut to size first and then magnetized. I want to try and take advantage of multiple designs by making a dual coil thin design. My designs are based on a different philosophy from Pete's, mix and match may not be worthwhile. Without some measurements and understanding, a dual core driver could turn out better or worse than a single core one - It has the potential to be better, but you gotta get it right for that to happen. I believe that there is very little point in trying to make super thin coils unless you are focused on piggy-backing them on a pickup as a priority. Personally I'm more interested in trying to use the driver as a pickup than piggyback a driver. cheers Col Link to comment Share on other sites More sharing options...
Donovan Posted March 24, 2009 Report Share Posted March 24, 2009 (edited) No data, but something tells me that the extra pole magnet that sticks out from the used up 3mmm of the bobbing adversely effects the sustainer... any ideas? I didn't understand that, can you try and explain again ? I've been using SC strat bobbins. Not the cheapo type with metal poles and a bar magnet (though I have a few of those as well), but rather 100% magnetic pole pieces. My construction has been: unwind stock PU, bock up all but upper 3mm, wind coil in upper 3mm. This leaves the lower remainder of bobbin empty except for the lower portions of the pole pieces (total height minus the 3mm coil). I've not measured it, but I'd guess it's around 7mm to 10mm. What is the effect of having these poles left in their entirety as opposed to having polepieces only within the 3mm bounds of the coil? I know this is a theoretical best guess type of question at this point, but intuitively, I would think there is some waste with the extra length or an increase in fizz or some other EMI-related philoso-babble. I add this as question number 379 under "sustainer questions that shall never be (other than empirically) answered". Intuitively, I would think the system would like it better to have an equally-sized permanant magnetic field both aboe and below the coil. I would also think that as is, there would be more phase lag or shift on one half of the AC wave form than the other as there must be some sort of effect on destroying and rebuilding the field in the opposite polarity. Edited March 24, 2009 by Donovan Link to comment Share on other sites More sharing options...
col Posted March 24, 2009 Report Share Posted March 24, 2009 No data, but something tells me that the extra pole magnet that sticks out from the used up 3mmm of the bobbing adversely effects the sustainer... any ideas? I didn't understand that, can you try and explain again ? I've been using SC strat bobbins. Not the cheapo type with metal poles and a bar magnet (though I have a few of those as well), but rather 100% magnetic pole pieces. My construction has been: unwind stock PU, bock up all but upper 3mm, wind coil in upper 3mm. This leaves the lower remainder of bobbin empty except for the lower portions of the pole pieces (total height minus the 3mm coil). I've not measured it, but I'd guess it's around 7mm to 10mm. What is the effect of having these poles left in their entirety as opposed to having polepieces only within the 3mm bounds of the coil? I know this is a theoretical best guess type of question at this point, but intuitively, I would think there is some waste with the extra length or an increase in fizz or some other EMI-related philoso-babble. I add this as question number 379 under "sustainer questions that shall never be (other than empirically) answered". Intuitively, I would think the system would like it better to have an equally-sized permanant magnetic field both aboe and below the coil. I would also think that as is, there would be more phase lag or shift on one half of the AC wave form than the other as there must be some sort of effect on destroying and rebuilding the field in the opposite polarity. The magnetic core will give you a weaker electromagnet than a good soft magnetic material - like silicon steel. I think its something to do with magnetic moments and reluctance... anyhow, the permanent magnet will resist the change in the coils field whereas a steel core would enhance it. If you reduce the magnetic poles to 3mm its unlikely that there will be enough permanent field to magnetize the strings - the pickup probably has just the right amount of permanent field. Why would the longer poles cause EMI ? I don't get it. Although you're right to call a lot of the talk of EMI on here philoso-babble. Magnetic flux is a necessary part of the process - we just need to have as much as possible of the varying flux from the coil over the strings, and as little as possible everywhere else. I don't know why you would want equal sized permanent magnet above and below the coil ? The field is not destroyed and rebuilt, it is reduced and enlarged. There will probably be some effect associated with the hysteresis of the core (is that not just an efficiency thing though?) To limit it you would want to avoid permanent magnets in the core and stuff like pure iron - best with more esoteric alloys. More significant possibly is the fact that the string is physically closer for one half of the wave than the other. The pull of the magnet is reduced with the square of the distance, so will be a lot stronger when the string is near the driver compared with when it is far. Another related effect is that any flux that gets passed to the pickup via the strings will be much more evident while the strings are closer to the driver. (this may be why the fizz is so nasal - more is getting through on that 'close' half of the waveform?) I have wondered in the past if it might be worth contriving some circuitry that increases the power when the string is further from the driver and reduces it when it is closer - an asymetrical drive signal - using some sort of 'squaring' circuit. This might let us take the driver closer to the pickup as it would reduce the problem of the strings as flux conduit. However it might also cause other problems like DC offset and audible distortion due to normal field coupling, so I've not got around to actually trying to design something to test the theory. Maybe that something that would be more practical using a PCM class-d type of drive circuit... Hmm, I guess that takes us back to an old question - why not only pull?... this is like the converse of that - why not only fight the permanent magnet. That would probably increase the need to start playing with rare earth as they will be less susceptible to losing their strength over time with the coil fighting them constantly... so many potential traps though... I'm rambling now... back to your drivers - why don't you try using one of the cheaper pickups with a bar magnet and steel poles ? you might find it works better or at least as well. cheers Col Link to comment Share on other sites More sharing options...
psw Posted March 24, 2009 Author Report Share Posted March 24, 2009 Intuitively, I would think the system would like it better to have an equally-sized permanant magnetic field both aboe and below the coil. I would also think that as is, there would be more phase lag or shift on one half of the AC wave form than the other as there must be some sort of effect on destroying and rebuilding the field in the opposite polarity. No...I don't think so...not in my experience anyway...look at the pickup/driver things or how others have successfully converted single coils. Typically magnetic poles are alnico by the way, but if you really wanted to they could be pushed down with a vice or something. If the coil isn't good enough, better to pull it apart and start again...another benefit of PVA for potting...easily comes undone. Perhaps part of what happens is that the signal drives the string and kind of lets go...or at least, attenuates the drivers magnetic field with the strings caught in it's sway.The shape of the field may not be relevant to the "phase" much at all. There may be no real difference as far as fizz. Potentially less if the longer magnets are attracting the field down into the guitar more than along the strings perhaps. The ideal is to have something that works efficiently enough that the minimum amount of power is required. Minimizing power obviously minimizes the amount of EMI coming out of it. One reservation with some dual coil designs may be that they lack the projection and need to compensate with increased power...but that is just conjecture and based on miniture designs with close RWRP poles. Nothing will eliminate the risk of fizz, a clean signal is probably a better strategy so that any fizz that might appear is at least not unattractive and distorted. Another reason to conserve clean headroom by lowering the power requirements to run it. I am not saying that the single coil is a better or even more efficient driver btw...but I am suggesting that it can be good enough to have minimal EMI and drive the strings quite hard, certainly hard enough. If you have made drivers...what has been the problem so far with the testing of them? You need to test them well away from other pickups if you have not completely bypassed them as in an installation (at least in my experience)...maybe yours are fine but the circuit or the installation is suspect...or maybe you are reaching beyond the capabilities of the simple version of the project (like avoiding rewiring and bypassing). pete Link to comment Share on other sites More sharing options...
Hank McSpank Posted March 25, 2009 Report Share Posted March 25, 2009 (edited) Ok, people....we have sustain! My first trial run tonight..... Conditions... An 8 ohm ohm single string driver coil potted with paraffin wax (about 400 turns of 0.15mm around about 1cm of 4mm mild steel 'core', a reasonably powerful ferrite magnet attached on one end, ). The input signal - my PC, running a Function Generator program(test tone generator - http://www.tucows.com/preview/240287) - Sine wave preset at 330hz (open top E string's frequency). This signal is feeding into a bog standard LM386 circuit... Results...... Well, in my humble opinion, the LM386 sucks. Firstly, it has a native gain of 20 (ie no resistor between pin 1 & 8) which I reckon may be too much for this particular coil. Observations... When I feed the LM386 with a stupidly low input signal (less than 50mV as shown on the scope - at this low level, it's even hard to see the input on the scope in amongst all the extraneous junk/noise), it still easily drove the string to excitation without needing me to pluck it first. Interestingly, the power amp worked best at about 5.5V rail. At this level there was no fizz' heard on the guira's output...below 5V fizz came in, about 9V a different type of distortion was heard (similar to the so called fizz...but slightly different in its characterstic) IMHO, if I can't get a sweet spot using a signal generator as an input (ie controlled conditions - no feedback loop to worry about), then I reckon there's not a cat in hells chance I'll be able to use the string as an input signal & have any degree of control ...ie to find that 'sweet spot' (the sweet spot being where no sustain is present until the guitar is plucked then the string sustains nicely). It seems to be a binary outcome...either no sustain, or self sustain. Next steps... I now need to find a driver output stage with less gain (initial thoughts are along the lines of a simple preamp feeding an amp supplying a 'constant current'...as per what Col touched on of late) I need to make a single sting driver coil with less windings (therefore even thinner wire than .15mm I'm using to meet 8 ohms) Use weaker magnets! Less magnetic material (steel) in the driver core! Oh yeah...as I said in one of my earlier posts...I knew I'd know very early on in my testing whether a cheeky 'card up my sleeve' would work or not - well it didn't. What was the card? Using Lorentz's force to displace a magnetic field with the signal feeding into the driver (the idea being to waft a magnetic field back & forth in the same way a plectrum applies force to a string). Have a look here, you'll see that they put the magnets on the side of the coil, *not* underneath... http://ccrma.stanford.edu/~sbacker/empp/what.html there may still be some mileage in this approach, but I now think it only works well in that scenario because they're chucking a *lot* of power at their coil (& don't need to bother themselves with EMI worries) I took some video footage of the guitar sustaining (& the what was seen on the oscilloscope). I haven't got time to upload tonight (it's late here in the UK)...hopefully tomorrow. Edited March 26, 2009 by Hank McSpank Link to comment Share on other sites More sharing options...
psw Posted March 25, 2009 Author Report Share Posted March 25, 2009 (edited) Well...it's so good to here you excited and it is producing some results. You may be getting some false impressions still...i know, I am sooo negative!...but my earliest experiments along these lines were very similar, small coils and thinner wires and the use of signal generators and such. Yes you can hit a resonant frequency with very little if an phase lag by tuning the string and the generated note through amplified sound card...but ultimately you need to be able to run it on any note, fretted anywhere and on any string from the guitar's own signal..and that's where things like wire guage and driver design (simple as it is) seems to have more influence. The reason I stopped (around page 10 i guess) using these kinds of things is because while I got similar results, it wouldn't transfer to the "real world" which is far more complex. As a result there may require more amplification (although i think col doesn't have the higher gain and mine is adjustable) and things like the zobel network to help things remain stable. I used signal generation signals because I was wondering if there was a preferential driving signal (like sine, triangle or square wave signals) for instance. But the input signal and preamplification is quite different from the signal of a real guitar, through pickups, generated from a different string sample and all the rest. Theoretically, if you could generate something of just the right resonance, it should take hardly any power at all to sustain, but this is very much an idealized situation that is very hard to transfer to the "real world"...if only for the fact that fretting in relation to driver placement must always change. Some of my hex designs also tried to simulate a more side to side or balanced kind of drive with novel magnet orientation...this caused them to be extremely sensitive to alignment. I was hoping that I could perhaps mount something in or just in front of a bridge...that is where the hex things were ultimately aiming, but I just couldn't achieve that. But I am glad that you did try the more basic approach so that you will be getting more of a handle on the device and the various "issues" and perhaps come to your own conclusions or at least inform your further adventures. There is always something magical when you do get those strings vibrating though...one of the happiest moments in my life was when my daughter got to play with it and the look on her face as this thing drove the string as if by magic will always be precious to me... keep reporting in... pete ps...400 turns seems a lot, must be a pretty small coil? Thinner wire offers more resistance so the number should be less. It seems very much like my original (page 2) 10mm single string driver on a ferrite core and similar wire gauge...that looked like it was going to vibrate the strings right off the guitar...it didn't scale up until I worked out a different wire gauge and gave it more power. The result did encourage me to attempt to make six of them, but then the EMI and power requirements were also multiplied of course! Edited March 25, 2009 by psw Link to comment Share on other sites More sharing options...
Donovan Posted March 25, 2009 Report Share Posted March 25, 2009 Why would the longer poles cause EMI ? I don't get it. Here I go again being intuitive. Let's call this extra length of magnet that hangs down "extra" for the moment. This extra length, is it being used? Is it not sending more magnetic flux laterally outward than shorter magnets of equal strength? You have gotten handy with some software that models fields, correct? Is this something you could model easily enough? Regardless, it sounds as though I am completely off base, but do you see where I am coming from at least? I don't know why you would want equal sized permanent magnet above and below the coil ? I mis-worded that. I want to not have the field so lopsided as it seems it would be in the configuration I have. Instead of equal magnet, I should have said equal field, as I would not expect that having much if any actual magnetic material above the coil is of use as it will put too much constant pul on the strings and at some point hinder any vibration. The field is not destroyed and rebuilt, it is reduced and enlarged. Isn't the entire field a sum of two components, a permanent field plus a temporary field's shift in one direction or another? So, whereas the overall summed effect is that the permanent field is weakened or made stronger, isn't this due to the continual destruction/reconstruction of the temporary portion in opposite polarities? More significant possibly is the fact that the string is physically closer for one half of the wave than the other. The pull of the magnet is reduced with the square of the distance, so will be a lot stronger when the string is near the driver compared with when it is far. Another related effect is that any flux that gets passed to the pickup via the strings will be much more evident while the strings are closer to the driver. (this may be why the fizz is so nasal - more is getting through on that 'close' half of the waveform?) I have wondered in the past if it might be worth contriving some circuitry that increases the power when the string is further from the driver and reduces it when it is closer - an asymetrical drive signal - using some sort of 'squaring' circuit. This might let us take the driver closer to the pickup as it would reduce the problem of the strings as flux conduit. Are you certain that fizz is due to the the strings acting as flux conduit? Brings me back to my original question about the extra magnetic material... I guess I feel fizz could be coming from the permanent magnets hanging down and emanating flux laterally. I never got fizz in the tests that I did holding the driver above the strings, upside-down. It only began occuring once the driver was actually installed to the pickguard. I then thought that some of it was due to shielding on the pickguard itself as Sustainiac removes the pickguard shielding, but then I installed the driver on my guinea pig strat, which is not shielded except for a tiny section, and the fizz is still as evident. Hmm, I guess that takes us back to an old question - why not only pull?... this is like the converse of that - why not only fight the permanent magnet. More of the intuitive. I have tried only pulling, figuring the temporary portion of the field would react quicker and it would be a power savings as well. However, testing I did was completely unsuccessful. If I had to guess why, I'd say the coil could be likened to a speaker, in that it can not reproduce detail perfectly and so rounds any sharp changes, much like a speaker rounds the corners of a perfect square wave. back to your drivers - why don't you try using one of the cheaper pickups with a bar magnet and steel poles ? you might find it works better or at least as well. I have no reason other than I guess I've grown discouraged and have been waiting for some materials to try something drastically different, but now that you've suggested it, I may. Thanks for the discussion. Link to comment Share on other sites More sharing options...
Donovan Posted March 25, 2009 Report Share Posted March 25, 2009 No...I don't think so...not in my experience anyway...look at the pickup/driver things or how others have successfully converted single coils. Typically magnetic poles are alnico by the way, but if you really wanted to they could be pushed down with a vice or something. If the coil isn't good enough, better to pull it apart and start again...another benefit of PVA for potting...easily comes undone. Does alnico have a similar appearance/feel as ceramic magnets or is it noticeably more metal-like? Perhaps part of what happens is that the signal drives the string and kind of lets go...or at least, attenuates the drivers magnetic field with the strings caught in it's sway.The shape of the field may not be relevant to the "phase" much at all. Perhaps. If only we could see this stuff! Nothing will eliminate the risk of fizz, a clean signal is probably a better strategy so that any fizz that might appear is at least not unattractive and distorted. Another reason to conserve clean headroom by lowering the power requirements to run it. Not sure I understand what you mean. I don't see the fizz as at all related to the signal being used to drive the coil. Should I? I am not saying that the single coil is a better or even more efficient driver btw...but I am suggesting that it can be good enough to have minimal EMI and drive the strings quite hard, certainly hard enough. I have been able to drive the thicker strings quite hard, but the B and E strings are not effective above about the 14th/15th fret. Also, I have never gotten a consistent fundamental mode or harmonic mode. I have been able to use 2nd order all-pass filters to shift the regions and harmonic around, but there is always a mix in some places, harmonics in some places, and fundamental in others, never just one solid mode everywhere. This is 100% consistent across multiple drivers, multiple circuits with different preamp and amp configurations and different host guitars. Always, I am accompanied by a good deal of fizz. When I dial the amp circuit back to where fizz is gone, sustain loss abruptly follows. If you have made drivers...what has been the problem so far with the testing of them? You need to test them well away from other pickups if you have not completely bypassed them as in an installation (at least in my experience)...maybe yours are fine but the circuit or the installation is suspect...or maybe you are reaching beyond the capabilities of the simple version of the project (like avoiding rewiring and bypassing). The problem has been consistency and strength on the B and high E strings above the 14th/15th fret. I have completely removed the middle pickups with no change in results vs. leaving the pickup installed and connected. Quite the opposite actually, I was able to get the same results using the middle pickup for the signal as the bridge pickup. I was originally using a test box with about a 2-3 foot in/out cable. All of my electronics were contained within a black box and I was building modular preamps, filters, and amp circuits as to easily connect/disconnect for testing. The results with this box were the same and when I brought my less than ideal results here, it was suggested then to ditch the box and do a direct install, biting the proverbial bullet. Again, the results are the same. I have fiddles with preamp gain, no preamp gain, 20X 386 gain to 200X 386 gain, driver distance to strings, signal pickup pole distance to strings, low pass filtering anything above 2kHz, all pass filters, half wave rectification, injecting all sorts of digital effects into the signal chain, all to no avail. I am at a standstill at the moment and have even considered biting the bullet and buying a sustainiac or fernandes system, if for nothing else to dissect the thing and make it all public (at least this should be simple enough for the driver portion) once and for all. You have consistently pointed to my driver being the issue over and over and I am convinced it is the biggest part of my problem. Hopefully, it'll get sorted. So, until I can build another driver... You guys are brilliant. Keep it up. I am still hopeful. Link to comment Share on other sites More sharing options...
psw Posted March 25, 2009 Author Report Share Posted March 25, 2009 Well...it's not unusual to have trouble with the high E and B strings...although, the b string is one of my better responding strings. I have found that long driver leads are a bit of an impediment...remember, these are effectively an extension fo the driver coil itself. I can't really speak to a lot of complex circuits, but have you tried something like a F/R as MRJ has posted or an equivalent? Without seeing, hearing and knowing what is being done my opinions may well be worthless. If you have built a driver as described, then it has proven to work under the right conditions. As far as seeing these things, yes it's tricky...but some of us have played with FEMM simulations...col more advanced than others...at least to get a visual feel for things like magnetic shapes. Alnico is what is typically used in fender style magnetic poles and are metalic. All the same, very prone to demagnetization (although they can be re-magnetized easily enough and are supplied that way from stew mac and others). Not sure I understand what you mean. I don't see the fizz as at all related to the signal being used to drive the coil. Should I? What we call "fizz" is the source pickup hearing and amplifying the signal coming out of the driver. The ebow also does this by the way which is often misunderstood. Worse case this produces squeal (oscillationary feedback) but even if power is low enough to stop that, the pickup may still pickup the magnetic variations coming from the driver as a signal. If that signal is distorted then that distortion will also be amplified...other effects may include phase cancellation and such that may make this distortion somewhat ugly. If the signal were "clean" (a big ask once mangled through the driver I imagine) it would be considerably less of a problem, most likely drive the string more effectively, resulting in less power being needed before fizz and as a result, less EMI and so less "Fizz". I think that your driver may well be effective...maybe there is something else getting in the way. A lot of fizz will definitely stop things working as it should, the first thing to go is high string response. Sustainiac and fernandes are good products...a little different in response than mine. We have pics of a completely taken apart drive and measurements of the coils. Some of the details are in the patents (though unreliable) but there are some "secret" epoxy coated stuff, especially in the fernandes and not enough detail. You clearly have tried a few things, but I'd be looking at short leads, a simple low power amp, battery not power supplied (can introduce noise), disconnect completely all pickups bar the bridge for testing, take the signal directly from the bridge pickup before the controls and send us lots of details ...it sounds like you have been getting close... pete Link to comment Share on other sites More sharing options...
Hank McSpank Posted March 25, 2009 Report Share Posted March 25, 2009 (edited) Well...it's so good to here you excited and it is producing some results. You may be getting some false impressions still...i know, I am sooo negative!...but my earliest experiments along these lines were very similar, small coils and thinner wires and the use of signal generators and such. Yes you can hit a resonant frequency with very little if an phase lag by tuning the string and the generated note through amplified sound card...but ultimately you need to be able to run it on any note, fretted anywhere and on any string from the guitar's own signal..and that's where things like wire guage and driver design (simple as it is) seems to have more influence. Well, a sine wave is the most efficient signal to throw at the sustainer ...& I've gone this route to get some handle on the power needed per string at the fretboard extremeties (& yes, under ideal circumstances). I think you're overcomplicating ....this is simply an early stage of noting down data. Phase lock didn't come into the experiment (after all, it was a free running sig gen)...& my initial experiment shows that when the power amp has too much gain, coupled with this particular coi (too many windings)....the string will 'excite' without any fuss. while gleaning this data, I don't have to worry myself about preamps, AGC, source pickups, etc. I used signal generation signals because I was wondering if there was a preferential driving signal (like sine, triangle or square wave signals) for instance. There is a preferential driving signal (I'm surprised you wouldn't know this?) a sine wave is it. But the input signal and preamplification is quite different from the signal of a real guitar, through pickups, generated from a different string sample and all the rest. Theoretically, if you could generate something of just the right resonance, it should take hardly any power at all to sustain, but this is very much an idealized situation that is very hard to transfer to the "real world"...if only for the fact that fretting in relation to driver placement must always change. Whilst I agree that a guitar signal differs from a sine wave somewhat, it would be quite wrong to dismiss 'sine wave input' data/results so early (this project needs more technical data... there's a fair degree of assumption, supposition, technobabble, myth & legend etc!). There are just too many variables initially that merely cloud the technical picture. For more 'real' world - well, once I've got sine wave results, I'll sample an open E string from the guitar into a wav file (& other strings), loop it & use that as the input signal to the amp , to see how it differs from the sine wave - I suspect not *that* much (& I just know that you're going to say "that's not real world, phase issues etc"...but we're just going to have to tolerate each other during my avenues of exploration in these early days!). Don't take this the wrong way, but it really is just stabbing in the dark without adopting - at least in part - a lab like approach (eg use a controlled input, monitor the output ....both audibly, visually *and* with test equipment.... observe/digest results...modify accordingly etc). Once I have something as a 'base', I'll obviously move over to the guitar as a real world signal (I can then just focus on the AGC aspect of the preamp) ps...400 turns seems a lot, must be a pretty small coil? Thinner wire offers more resistance so the number should be less. It seems very much like my original (page 2) 10mm single string driver on a ferrite core and similar wire gauge...! I just checked, but the photos have gone....I'm figuring that 5 years is more than can be expeted of any website to hold on to the photo! (I can clearly state now...in the year 2014, I will not be referring anyone back to my youtube video below!) My 'first run' single string driver is about 8mm wide & 10mm deep. I'll wind a smaller one once I get some thinner wire. (& yes, I know thinner wire = more resistance! See the video below) Here's a unedited short video clip, showing the initial basic setup and the driver (taken on a simple little point & shoot still camera, therefore not exactly high fideility...also it was raining hard & I was in the loft - so I call this one "guitar sustain sounds accompanied by rain on slate")... http://www.youtube.com/watch?v=ICa8zgd5Vp8 The point to underline, is that even though the signal across the coil is ugly the string does sustain cleanly (though I can get the string to oversustain by simply upping the sig gen signal). Also worth noting that even though I'm using a DC blocking capacitor at the input, it looks like there some sort of inbalance to do with the LM386, as initially there's only half the sine wave, until I crank the input signal up[ a lot. Since we're talking about 800mv of (ugly) sine wave across this 8 ohm coil...(therefore we could use a 1.5V AA battery for a sustain circuit!)... back of the fag packet calculations suggest (ie for this particular coil @at 330hz)... 800mV peak signal 565mv RMS current = 70mA power needed to sustain string one string 'just at the edge' = 112mW That said...it's been a while since I had to use such calculations & I'm sure someone might be able to pick holes in them! Having slept on this overnight - I'm now reasonably convinced that the LM386 chip is not the best chip to use here. Sure, it's cheaps as chips (no pun intended) & it'll get you your sustain (& plenty of it)...but if you want more control/granularity of the sustain across the guitar's frequency band (including harmonics), then it's gonna need a different output stage ...a voltage gain of 20x is just too much. For example, Put in a small 50mV signal & you've instantly got 1V across the driver, which in my opinion is too much drive for the string. Far better to use the preamp to 'control' the guitar signal, matching it with a lower gain output stage to ensure that the peak signal needed (whatever it is for your own driver) is capped & arrived at smoothly Edit: Just found a supplier of 0.063mm diameter wire (ordered some)...this should allow me to get the turn count down to meet 8 ohms. Edited March 25, 2009 by Hank McSpank Link to comment Share on other sites More sharing options...
psw Posted March 25, 2009 Author Report Share Posted March 25, 2009 My apologies...Hank I had a longer post typed, then i went back myself to page two where I gave very accurate description of the coil (12mmx4mm on a ferrite bead with 4 ohms of 0.2mm wire). No pics at that satge, photobucket didn't exist, I was taking "photos" with a scanner (you can still see some of the hex things that have a babies nappy over them!) as I didn't have a digital camera. I realize looking through those threads that I sounded just like you hank, and was doing similar kinds of things as best I could... By the middle of page 7 I posted this... Well if we had an o-scope and knew how to use it we could mabe debunk the phase difference I guess...anyone want to try out there!!!!! Meanwhile...yep, stomp boxes galore. I tried to use a flanger as a means to alter the phases on my original experiment years ago. What I got was a real interesting sound as it would catch a frequency (harmonic) then drop it as another would predominate and the rate would change as the harmonics got closer at either end of the sweeps...interesting. I'll try a fuzz as well to get a square wave. I've got a tone generator on the PC so I thought there maybe a way of optimizing coils by testing with pure tones and measure it's response somehow...any ideas there? Meanwhile, I'm gearing up to make a hex piezo undersaddle PU for the test strat as a source for each driver...be great to get acoustic sounds and infinite sustain and the posibility of hex effects. Perhaps a simple midi out breakout box to drive software sequences and notation software... Well, maybe... baby steps psw There was "lively" conversations back then as now, but perhaps I am short on the encouragement that was shown me in the beginning...a lot has happened since those days. Much of what people are discussing was being explored and discussed back then and probably is well worth a read I guess for others embarking along a similar road. I am curious from your vid though hank...what happens when the guitar is plugged in? pete Link to comment Share on other sites More sharing options...
Hank McSpank Posted March 25, 2009 Report Share Posted March 25, 2009 (edited) I am curious from your vid though hank...what happens when the guitar is plugged in? pete I have no big reason to plug the guitar into an amp at this prelimary stage ..as mentioned, this little workshop is in my loft & I don't have any amp facilities up there! (I will be knocking together a small breadboard amp circuit to do this soon)...I do have a guitar effects footboard that I could plug it into that has a headphone out (which I'll do tonight - * I might redo the video as the acoustic sound is masked somewhat by the ambient noise) At this stage I'm not using the guitar signal 'in the loop' so to speak...I can quite clearly hear acoustically that the sustained sound is clean...therefore the string isn't being overdriven (just like a guitar string sounds a short while after being plucked & as decaying). That strat will have a pickup disembowelled tonight & I'll nick the copper off it (it'll almost certainly be using 42 AWG, which is about 0.063mm...this should be perfect). I'll propbably also use the strat pickup bobbin as a donor 'six string driver' holder too! I've now got my Google hat on searching for a suitable lower gain output stage. Edited March 25, 2009 by Hank McSpank Link to comment Share on other sites More sharing options...
psw Posted March 25, 2009 Author Report Share Posted March 25, 2009 Hmmm...looks like I have missed a couple of posts there between col and donovan. I'll restrain myself at 1am! I do note that both are talking about non-sine wave signals and again, much of this was also discussed along with some debunking (perhaps) of phase issues and patent reading by LK and more between page 2 and 7 and beyond! I think the ideal signal may well be the undistorted signal of the strings real vibration, in perfect phase! But, I did wonder if a saw tooth wave might help with any phase concerns back then and worth a shot. As I recall, with experiments very similar to hanks, there was little driving difference whatever signal I used, they all worked! The problem was the EMI and fizz that could result should these signals get into the source pickup, which is a whole different ball game. FEMM is limited, it's 2D and the way I used it pretty crude. I am kind of with donovan, although I think you are talking about similar things in relation to the alternating reducing enlarging, fields...this is where I talk about "speed" and everyone hates me saying that. Basically, you need to establish a field (or enlarge the existing one), overcome this enlargement (this produces a lag) and then release or reduce the field "fast enough" for the vibration of the string. When we looked at square and half wave approaches (someone referred to this as "pinging" the string) I came to a conclusion that you needed an opposing signal to collapse or reduce the field (it won't want to release unless it is pulled the other way). This is most apparent with the higher strings which are vibrating a lot faster. No...I do not think that the long magnets make much difference. You have a permanent magnetic field and you are manipulating it, the shape of it may make a difference to EMI issues, but not so much if it will drive the string I suspect. In relation to the thin coil and the piggy back driver. The piggyback thing was an afterthought...this was not the intention of the design, the design was created as the most efficient in comparison with others (deeper coils, etc) and not what I set out to do. The piggyback concept was not the aim. The recent tele thing was probably more what I had in mind, but even that was because the most effective design that I could come up with could be utilized in a very compact form. The compact form came about as a direct result of the hex things which became ridiculously small, when challenged I offered a DIY-able working version of the kind of things I was working on fully expecting to return to the hex things. In trying various things, I came to the idea that one of the reasons I was getting some superior results in EMI reduction may well not be from some of the exotic materials and magnetic orientations, but simply because they were so small and focused. This thought made me seek out something that was as compact as possible to exploit this as much as anything. But this is something I have explained before. We all have different desires I guess and different roads to travel to get there. I have included in my itinerary a wide range of things...simple enough to DIY (my hex things were way over the top for that), compact enough to allow choice of pickups, low modification of existing instruments (the piggyback driver, the tele surface mount driver), simplified basic circuits...but most of all something that would produce "the" effect, or something close to it! Perhaps I have been seduced by the results and not taken it "further" as I had once so enthusiastically tried. Maybe I have just been doing this too long. So much has changed in all these years. In fact, i get quite emotional recalling those times compared to now. I had a house where I could do these things, I had days in which a baby slept and time to tinker. All those things have gone, I haven't seen either of my kids (my son hadn't even been born when this started) and I haven't seen either of my children for a year this month. I have a house inspection again today that may see the sale of the house I rent and some permanent changes, perhaps even a complete enforced retirement from this kind of thing...so there are a lot of "issues" at play here. All I can say is that I am sorry if that jaded negativity is to the fore and go back and read the words of encouragement that others offered from the beginning on all these issues and more, see the kind of things I was doing back then and the amount of work that was behind those things. These days I am acutely aware that I am no longer active in creating these things, but as the only one who has traveled the whole journey of this thread, believe me that I did an enormous amount of work to back up those early threads, much the same ideas that are being discussed here again and my posts read uncannily like those of donovans and hanks today. enough...i will try and sleep... pete Link to comment Share on other sites More sharing options...
psw Posted March 25, 2009 Author Report Share Posted March 25, 2009 At this stage I'm not using the guitar signal 'in the loop' so to speak...I can quite clearly hear acoustically that the sustained sound is clean...therefore the string isn't being overdriven (just like a guitar string sounds a short while after being plucked & as decaying). Yes...but you are not hearing any fizz or EMI issues...the noise doesn't come from the string, the string can be sustaining away very vigorously and still have massive amounts of fizz and EMI and things like the leaking of such things through the ground connected pickup coils (if such things occur as suggested) may be very important to your future plans, or at least put those things to rest. But carry on... pete Link to comment Share on other sites More sharing options...
Hank McSpank Posted March 25, 2009 Report Share Posted March 25, 2009 (edited) At this stage I'm not using the guitar signal 'in the loop' so to speak...I can quite clearly hear acoustically that the sustained sound is clean...therefore the string isn't being overdriven (just like a guitar string sounds a short while after being plucked & as decaying). Yes...but you are not hearing any fizz or EMI issues...the noise doesn't come from the string, the string can be sustaining away very vigorously and still have massive amounts of fizz and EMI and things like the leaking of such things through the ground connected pickup coils (if such things occur as suggested) may be very important to your future plans, or at least put those things to rest. But carry on... pete Yes, I know there'll be EMI to deal with ...but once again, this is a data gathering stage towards a suitable hex driver and amp design! (specifically power levels into the driver). You really must try & stop assuming that you've all angles covered & that others haven't - I know what I'm doing ....I'm not here because I'm clueless & want to ponce info off others towards a cheap diy sustainer. Let's ground ourselves here - a sustainer project isn't exactly the inner workings of the Hubble Space telescope reflector - at its most basic, it's a simple low power audio amp driving a simple coil! No, I've pitched my trailer up here to be amongst like minded individuals & share info, with a view to different sustainer designs/avenues - not to be patronised. I could almost stomach the constant "been there..done that" stance you've adopted wrt everything I'm posting...*if* you could give me some tangible technical data, but correct me if I'm wrong, you aborted the hex concept without a replicable solution (& have you ever wondered why - as you keep saying - so many pass through this thread then disappear?!). You've served the internet community extremely well with your thin sustainer driver info, but there are *many* more ways to skin a cat - if all you can now do on this thread is look for the bad in everything that doesn't fit your model, then in your shoes, I'd be wondering if it's time to say let it go. While I know EMI *will* be a problem (& will need eventually addressing 'creatively'), I'm expecting it to be less of a problem than your mono driver.... due to their being less power being applied across a smaller drivercoil. I'll tackle the EMI later, once I've got the best combination of hex coil & circuit - but one thing I'm shooting for....is the least power to the coils possible (which in turn ..the least 'spread' of EMI). I'm wondering if this is why you're all struggling to contain EMI...an LM386 at its default 20x voltage gain is always going to result in a fair amount of current into the driver (even quiescently). So at a miniscule 5mV guitar signal input, the LM386 you're going to have something of the order of 80-120mv across the coil ...sufficient to spam your other pickups with EMI. Edited March 25, 2009 by Hank McSpank Link to comment Share on other sites More sharing options...
Leppard84 Posted March 25, 2009 Report Share Posted March 25, 2009 Donovan, I really like your idea about de-bugging a Fernandes sustainer. I tried making one using your guide on this excellent learning webiste and my first few attempts could not create a driver that worked. That was over a year ago, since then I bought a Fernandes, to bypass my own building frustrations, only to break the trim pots on the install. Therefore, I do have a Fernandes circuit board for us to take a look at. I'll try and post some pics tonight after I'm off of work, maybe we can gain some insight into what they are doing and firnd a simpler way of going about it! But it is an idea I like. As for my driver, I finially have one that reads at 10.2 ohms on my DMM!!! Close enough for now, I don't have an oscilliscope like many of you might but I'm diving in full force to aid in testing of circuits. Talk to you all later, ToNy Link to comment Share on other sites More sharing options...
col Posted March 25, 2009 Report Share Posted March 25, 2009 Ok, people....we have sustain! My first trial run tonight..... Conditions... An 8 ohm ohm single string driver coil potted with paraffin wax (about 400 turns of 0.15mm around about 1cm of 4mm mild steel 'core', a reasonably powerful ferrite magnet attached on one end, ). The input signal - my PC, running a Function Generator program(test tone generator - http://www.tucows.com/preview/240287) - Sine wave preset at 330hz ( That's good progress. One thing I would suggest is don't use 330Hz as a test frequency - that will potentially give you over optimistic results. A coil with as many turns as yours will likely have a MUCH higher impedance at higher frequencies. e.g an 8ohm 6mH coil (yours may be more than that) will have an impedance of around 14.5 ohms at 330Hz. At 660Hz it would be 26ohms and at 1320 (24th fret?) the impedance would be a whopping 50ohms. A high inductance driver like this will push the strings very hard with relatively low current at the lower frequencies, but struggle badly at the higher frets. To avoid potential dissappointment, it would make sense to test at a higher frequency - say 1000Hz or 1200Hz ? That way you know you will have at least as good a response for the full frequency range of the guitar. Stick a capo of some sort on so you don't have to hold the string down to run the tests. cheers Col Link to comment Share on other sites More sharing options...
psw Posted March 25, 2009 Author Report Share Posted March 25, 2009 That was over a year ago, since then I bought a Fernandes, to bypass my own building frustrations, only to break the trim pots on the install. Therefore, I do have a Fernandes circuit board for us to take a look at. I'll try and post some pics tonight after I'm off of work, maybe we can gain some insight into what they are doing and firnd a simpler way of going about it! But it is an idea I like. As for my driver, I finially have one that reads at 10.2 ohms on my DMM!!! Close enough for now, I don't have an oscilliscope like many of you might but I'm diving in full force to aid in testing of circuits. Talk to you all later, ToNy I'd like to see some pics and details on their driver. As for the board, you are not the first to have trouble with the trim pots and there are a few posts on fixing them around the electronics section as I recall that you might want to search out. Sorry you didn't get the project to work, both fernandes and sustainiac make good products...personally I have a bit of a bias for the sustainiac as it seems a bit more flexible in the installation and aftermarket support and as I say, yours is not the first one that has trouble with the trim pots. pete Link to comment Share on other sites More sharing options...
col Posted March 25, 2009 Report Share Posted March 25, 2009 The point to underline, is that even though the signal across the coil is ugly the string does sustain cleanly (though I can get the string to oversustain by simply upping the sig gen signal). Also worth noting that even though I'm using a DC blocking capacitor at the input, it looks like there some sort of inbalance to do with the LM386, as initially there's only half the sine wave, until I crank the input signal up[ a lot. Since we're talking about 800mv of (ugly) sine wave across this 8 ohm coil...(therefore we could use a 1.5V AA battery for a sustain circuit!)... back of the fag packet calculations suggest (ie for this particular coil @at 330hz)... 800mV peak signal 565mv RMS current = 70mA power needed to sustain string one string 'just at the edge' = 112mW That said...it's been a while since I had to use such calculations & I'm sure someone might be able to pick holes in them! 70mA and 565mv => 39mW. That seems very low. Possibly a combination of no adverse phase cancellation and using a higher inductance coil (try that at 1200Hz) Having slept on this overnight - I'm now reasonably convinced that the LM386 chip is not the best chip to use here. Sure, it's cheaps as chips (no pun intended) & it'll get you your sustain (& plenty of it)...but if you want more control/granularity of the sustain across the guitar's frequency band (including harmonics), then it's gonna need a different output stage ...a voltage gain of 20x is just too much. For example, Put in a small 50mV signal & you've instantly got 1V across the driver, which in my opinion is too much drive for the string. Yes, the LM386 is not ideal - we could do without the gain - just an on chip power stage would be really cool. The first thing I did when I first tried this project was minimize the gain. It's really annoying, and must cause significant noise issues having to siphon off so much juice before the LM386 input only to apply all that gain to the noise added by the resistors... aaarrrrgggghhh The thing is though that building a power stage from discretes has a whole bunch of extra pitfalls - its nice not to have to think about those. Anyone know where there's a chip with just a push-pull class AB power stage with nice pinout access to the internals ? cheers Col Link to comment Share on other sites More sharing options...
Recommended Posts