Help With My Sustainer

[psw]

The thing about the basic 'diy sustainer' is that it is designed very much like a fixed six string ebow...very simple...and so the the circuit is very much exactly like that of the ebow and the performance much as you'd expect from such a device. The driver is designed to work from that system.

The fetzer-ruby was never my suggestion nor recommended by me or many others. It was always poor in that it lacked the essentials for high gain LM386 applications that the data sheet requires and the biasing that is recommended...but how many have offered alternatives specifically and especially for "this thing". Hardly anyone has the same criteria or prepared to put that out there, let alone the circuits that they use in any real detail. I've always said i didn't like it, always provided the minimum to "fix" it and always pointed out that I was getting success with a number of generic basic non-loading amp designs...it was just not the determining factor in the basic success of sustain and harmonics on all strings.

But the F/R could work and even has in the basic form...for the "ebow like" ethic...all that is needed is a non loading section to avoid problems with the host pickup and a power amp...usually a bit of biasing to taste and response. As most people who have trouble building even the F/R successfully and often the drivers are suspect as well...it is no wonder that some have problems with the enterprise.

If you get things to work efficiently and find the right balance at low power, you will automatically have AGC as the circuit will reach it's maximum power running off a battery limiting itself....there is not an imperative to get over complicated about it. No one would accept a given circuit anyway. Col's circuit is still available yet no one has replicated it ever...one wonders why. Obviously these circuits do work and provide the basics as it has been done time and again and sound clips are available.

But lets face it....the people who would seek to debate it all have different driver designs...FF, Col both use different unspecified dual coil designs for instance and hardly anyone has tackled the multi pickup difficulties. And where are the circuits and criteria required...what size are these things...how easy would it be to replicate for the DIY'er...where are all the "instructables" from others who have found their own way over the years?

It's all very well for people to sign in under a name to poke at not being spoon fed these things and at the originator...but that was never the intention nor my responsibility alone...but it certainly comes across that way as if I want to be considered "clever" when I'd really like to see some clever solutions on offer from others and the criteria that support them and from which to measure their success.

All the original sustainer designs were based on the "ebow assumption" with basic amplification...the drivers were built to these circuits. They were built from generic preamp kits and LM386 data sheet kits with a bit of a mod to the output cap to 100uF to suit my tastes and driver designs and source pickups. The F/R came later and others picked up on this despite all the mods and warnings about it as being a bit clunky. Lovecraft was right from the earliest days...design the driver to the basic amplification and ignore the patents and phase circuitry and AGC...consider the ebow!

Now...a bit of AGC might refine things...listen to cols and you will see it has a different performance criteria...always wanted a very controlled and fundamental sustain especially in low notes and his circuit achieves that. For me, I wanted a far more dynamic sound and liked the 'bloom' especially in the low notes. For both of us, battery power was essential as was a smallish circuit.

For me, I needed to have all pickups available and no compromise to the host guitar...for most it seems that a single pickup guitar is adequate. If there is too much diversion in the driver...you might get more "power" but a completely different resonance say in the low frequencies or like sustainiac and all others, the need to compensate for phase and such. If this is the road you are on, then your circuits will need to be more sophisticated...but is the added performance there to warrant it, i can't tell.

Gmike used a slightly different wire and a bad choice of magnets and core...and got poor high string response...the tutorial presented before it was truly successful or even installed. Mine at the same time, and what it was based on, built to spec with generic amps worked ok...and I believe even Primal's with the F/R as is worked straight out of the box in an LP. For some reason the F/R is somehow associated with me...but I was always concerned not to 'steal' the work of others like RoG and that such a circuit was ideal for the application.

It just depends on your criteria and philosophy about these things...the ebow patent specifies "any suitable amp known to the art", and so that is what I suggest and tested many different basic amp designs and chips...that in fact they have and always used LM386's says something but purely incidental to it's function. Based on the same principle...so to the basic DIY sustainer. Ive used op-amp buffers and JFETS and push pull transistors and all manner of things, all easily available and widely known...even a full on compressor limiter at one stage...but in the end, to meet my criteria it had to be simple and compact and work and worth the effort. I've made dual coil drivers, even hex drivers...but they have not stood that test for me...a lot more work, no more gain...harder to meet the other criteria...usually losing a pickup along the way.

But the whole "circuit" thing is a furphy if one considers the ebow as the starting point and work up from the most basic working model and perfect that. There is no "ultimate" or "perfect' sustainer except within the personal criteria of the builder and performer and the particular guitar and application. Since everyone is a bit shy to lay even their criteria on the table let alone the detail of their designs (mine was laid out in the early 30's of the main thread)...it seems that I cop the flack as if I have any responsibility any more than others do. And lets face it, there are people who claim more expertise and equipment than I ever have and nothing much has come of all this at all in years of trying...just more elaborate pseudonyms to push the circuit side of things...and pretend the driver or even the battery don't matter or arre not intrinsic parts of the circuit and 'system'

[big_boleros]

Mr Fizz - tks for the Galaga Mike tut - very clever.

Scoop 'n Daddy.

Edited December 13, 2010 by Prostheta

[psw]

Why would anyone who is interested in building sustainers not prefer circuitry designed specifically for sustainers over a general purpose mini power amp?

Because the basic DIY sustainer was conceived as a static six string ebow and as such. An ebow runs of an even simpler basic amp than the fetzer ruby. It is an elegant simple solution and like the ebow patent..."any known amplifier circuit known to the art" (of electronics) is specified.

The basic driver then was designed, along with the limiting of the battery (as a crude AGC in itself) as a total system that works in this manner with any such basic low powered circuits. Other than the addition of a buffer stage to prevent loading on the guitar itself, it is remarkably like the classic ebow circuit, even down to the LM386.

I wonder why people feel the need to make it so much more complicated as it needs to be?

Perhaps since the BB or whatever he will call himself next isn't asking for your circuit FF...perhaps a few pics and the criteria that informs it and some sound clips would help gauge the more complex is better side of the debate.

If people really want to build "their own" sustainer, perhaps they need to be the kind of person that, like me, can do some solid research and experimentation and show some actual results...and prepared to stand by it.

[therizky]

"Hey man without quote button, rolleyes.gif"

lol

i need to take some time to learn on how to use that ****.but im fine so far.

I can't offer anything from col's circuit design. Even if I had it, there's ownership rights that have to be respected. :aureole:

i didnt ask you to do that anyway,i was asking for you to draw me some simple original schematic. c'mon,read my post carefully.

"The whole agc thing is nothing more than some kind of compressor/limiter that has to be transplanted into your sustainer circuitry. So best to take a look first at the tangerine peeler which has feedforward as well as a feedback sidechain.

Filters, no! Ldrs are used in compressors like the flatline compressor (not feedforward). So ldrs yes if you know how to do it!"

ldr? no,i don't know how to do it.lol .the tangerine peeler blows big time anyway. ou well...since the goal of agc is to save power and energy. why don't create something that limit the use of power directly at the power source (+v) ? or the result is pretty much the same?

not so long ago i tried to run dod 280comp,which is ldr based compressor with no subtle result.

now i'm going to tried to build escobedo's uglyface,and run it as sustainer circuit. since it has threshold and frequency control,it think it has the ability to control the desired dominant frequency response of the sustainer. no?

edit:a few days ago i read wasp whining about driver design and now there's another guy mumbling about circuit. phew,i guess this diy sustainer project can't get any more clear and simple. sorry for the late reply anyway

hehe peace!

Edited December 13, 2010 by therizky

[big_boleros]

If you change things, such as to a thicker wire, you will require more turns and radically alter the resonance and response characteristics and slowing down the alternating EM action...so it will have phase problems and have to be corrected with circuitry.

You might want to revisit your sources! If you increase the size of the wire (and shoot for the same DC resistance - I assume you missed that bit), it will increase the inductance of the driver coil, which in turn will impede the higher frequencies into the coil, but it won't slow the alternating EM action down (now that *would* be clever!), there'll just be less EM strength (drive). The resonance of a driver is already *way* above our band of interest so a few extra turns is of no significance to even warranting mentioning it..

IMHO phase correction is a bit of anomoly here too....you sort one frequency, you introduce probs with other frequencies! It may well be that the commercial sustainer companies have decided that the impact of assisting the weakest link, is a one worth living with ....but phase compensation is a bit of a grand term (two caps & two resistors!)- I'd say it's more likely to be basic frequency compensation (tarted up as phase compensation for the patents - smoke & mirrors), but this in turn, introduces phasing problems.

[Fresh Fizz]

You guys do realize that the sustainiac river is a completely different animal? It is a bi-lateral dual coil, broad laminated core pair that functions as an active neck pickup as well. Each coil is less than half the length of the standard pickup or single coil driver.

Split coil like on Fender precision basses, huge core like some high output humbuckers (+ agc design that allows for a higher self-inductance). My driver functions as neck pickup too.

You are running a power amp from a battery, there is no getting around the fact that you are going to be drawing a lot of power from a small power source...you will never get the kind of draw that you might expect say from a fuzz box that is only modifying a signal, that amps clearly state that it alone is drawing perhaps 1/2 a watt of power..plus powering any other gadgets, filters, AGC's and such on there. FF has an entire stompbox compressor running in that thing, so it alone would kill a battery reasonably quickly before we even get to a power stage. Battery power is clearly not a criteria for FF and others and is designed with this in mind, fair enough too. Everyone has different criteria and many have alternate designs that are not comparable. The best one can do is to listen to the results and balance them with your own criteria.

This was Wasp's question:

The commercial sustainer companies speak of 20 hours from a single 9V battery - that's impressive from a power source only capable of supplying 550maH....just wondering what the 'best in class' DIY sustainer gets out of a 9V battery?

To me it seems that Wasp knows what he is talking about. The commercial ones are not drawing 0.5 W, because of the use of agc.

But why don't you answer the question?

I chose not having to use a battery. That doesn't mean that my sustainer consumes more power than yours.

On the contrary I would say. You talk about balance but what you're doing is pushing the battery to its limit. To say it in your jargon: Exhausting a battery as quickly as possible seems to be one of your criteria.

Is the power consumption of a compressor more in the range of a fuzz box or of a mini power amp?

It's not that other formulas can't work...but hours of testing and independent confirmation over some years has indicated for the simple design (and that design alone) there is an optimum formula that provides the capacity for efficient driving of all strings with very low and basic amplification.

Now I'm a bit confused (cannot compare..., own criteria..., optimum formula?)

If you had said easy to build especially for n00bs, no difficult setup, will fit inside the guitar...

cheers

FF

[big_boleros]

It's not that other formulas can't work...but hours of testing and independent confirmation over some years has indicated for the simple design (and that design alone) there is an optimum formula that provides the capacity for efficient driving of all strings with very low and basic amplification.

Big Hmmm with that one.

Can you define efficiency here? In the light of FreshFizz's quotes from earlier on in this thread, I've just gone back to read in full - I agree with Wasp's comments...efficiency (certainly where a battery is involved), to most would mean optimum sustain with the least battery current draw - is that your take on efficiency too? If it is, then to claim 'efficiency' wrt driving of all strings must mean you've collected current draw data while conducting your tests?

So what kind of current draw are you seeing with you driver coil?

[Fresh Fizz]

not so long ago i tried to run dod 280comp,which is ldr based compressor with no subtle result.

now i'm going to tried to build escobedo's uglyface,and run it as sustainer circuit. since it has threshold and frequency control,it think it has the ability to control the desired dominant frequency response of the sustainer. no?

The best thing is to try out the uglyface for yourself. But I think you're able to achieve much better results with the dod280.

A. The distorted sound of the uglyface gets blended with the sound of the sustaining guitar string. The string serves as some kind of reverb spring for the distorted overtones that's emitted by the driver. But the frequency response is not flat, which is demonstrated in Tillman's applet . Move the pickup towards the bridge and you lose the lows, fizzy fuzz on top of the original clean sound is the result.

B. A compressor (limiter) with a slow release time acts less aggressive than a distortion box. A distortion wants to sustain immediately but a compressor sags during the attack and needs to recover. When you use a lot of compression you need a long release time.

...since the goal of agc is to save power and energy. why don't create something that limit the use of power directly at the power source (+v) ? or the result is pretty much the same?

You want to limit the available headroom and let the lm386 clip the signal? I don't see what's so magical about an overdriven lm386. Wouldn't a clipping device and a master volume before the lm386 work just the same? But if you want to go crazy experimenting I have something for you. Like a power soak, place a small resistor (4 - 8 ohms/1W?) in series with the driver. Or like a tube rectifier, place a resistor (47 - 100 ohms/1W?) between V+ and the lm386 pinout 6 together with cap.

Of course at your own risk, cheers

FF

[psw]

There is nothing "magical" about an overdriven LM386, any amp chip could run it...one tries to avoid overdriving the things, their gain is adjustable and as explained, the "preamp" is only required to prevent loading on the guitars pickup. An ebow uses am LM386 with very little else because it has a separate pickup coil in it that matches the LM386 input impedance.

The basic sustainer that I presented is simply a six string fixed ebow and has similar ambitions and results.

My "criteria" were put forward and developed in collaboration many, many years ago and published here...other people may have different criteria...other than Col, I don't recall them being put forward.

The commercial units use frequency variable phase compensation circuits...the "resistor and cap" thing is purposely superficial...the floyd rose patent is quite clear...a circuit senses the frequency of the input and adds "resistor and cap" style compensation of different values according automatically varying with the incoming signal.

I don't know where the idea that an AGC is there to to 'save power'...it has always mainly been about controlling the performance and response of the effect. There is often a power saving in some designs because excessive drive is reduced when the string is sustaining as desired, similarly 'fizz' and squeal thresholds are controlled because the feedback loop curtailed instead of continuing to build. Col for instance sought a very controlled even response...while I desired a more dynamic "organic" effect...both are equally valid and put forward and achieved. Power might be saved by AGC but some designs may well take up more power to run the circuitry...but this might not matter if the criteria set does not require a battery anyway....so you could run as much circuitry as you can fit in the guitar!

There are many ways that one could develop AGC for both response and power saving....shutting down the entire poweramp periodically, for instance, is likely to produce both effects...just a thought. The tacking together of other signal processing circuits as is being suggested is no different from the F/R and is not moving towards a dedicated circuit for this application IMHO.

The battery can be an effective AGC component...it ultimately limits the power available...but there is not the need implied that you need a lot or any 'preamp power' over a buffer or even to run something like an LM386 at full power. Few of mine other than the tele could take that much power before squealing. But certainly there is nothing magical about an LM386 or any other amp chip. Anyone who puts a circuit up that even contains an LM386 will only attract and goad the troll...or at lease give the impression that the LM386 is some kind of magical thing...this has of course been strongly resisted...just like the ebow that it is modeled on; "any known amplifier" is capable of doing the job.

Perhaps other successful "eggheads" and proponents of AGC might like to pass on to those calling for answers the details of alternate designs to mine...the specs of a dual coil driver, the circuitry, the installation and the criteria...maybe some sound. For all anyone knows, we may be comparing chalk and cheese. I didn't set out to produce a "sustainiac" or replicate that sound and response, I only set out to please my own criteria...everyone else may have different criteria and certainly different guitars, source pickups, installations and abilities to build and or design circuits and drivers effectively.

This is a DIY project after all, not a "product" and the design on offer can be built and clearly works for many with very simple circuits and driver specs...as far as the basic sustainer is concerned, that is a part of it's criteria. Things like my hex drivers and some circuit ideas were beyond that criteria and so not 'disclosed' because what would be the point if it couldn't be replicated effectively by others.

No one complains that an ebow only has a basic LM386 circuit and no AGC or more complex circuitry...I don't see why it should be of such a concern for others other than beyond the most basic forms of this kind of thing. If people can't make even the most basic proven design work, adding more isn't likely to make things better till one does.

[psw]

It's not that other formulas can't work...but hours of testing and independent confirmation over some years has indicated for the simple design (and that design alone) there is an optimum formula that provides the capacity for efficient driving of all strings with very low and basic amplification.

Big Hmmm with that one.

Can you define efficiency here? In the light of FreshFizz's quotes from earlier on in this thread, I've just gone back to read in full - I agree with Wasp's comments...efficiency (certainly where a battery is involved), to most would mean optimum sustain with the least battery current draw - is that your take on efficiency too? If it is, then to claim 'efficiency' wrt driving of all strings must mean you've collected current draw data while conducting your tests?

So what kind of current draw are you seeing with you driver coil?

No...not to do with battery drain. It is to do with the ability of the driver design and construction to be capable of driving all strings effectively with basic amplification...ie, no variable phase compensation, no AGC circuitry, no squeal and none or minimal distortion. Obviously if you can do that "efficiently" you are likely to also draw less power as a consequence, but that was not the aim. The aim was to efficiently drive the strings with the least amplification and circuitry and keep things as simple as possible...run the amps as cleanly as possible and reduce power to reduce the effects of EMI in the system.

An "ultimate sustainer" is not necessarily as 'wasp' would have it, the one with the longest battery life. There is no "ultimate' but regardless, it should be about performance within a given criteria...if long battery life is a part of that criteria or top of the list...then perhaps that is "ultimately" the most important thing for him. Most have traditionally aimed for producing the effect they are after above those aspects.

As stated though, mine is still going on the same battery with the intermittent use I give it for months now...the commercial units can not do this because they require a battery for the whole guitar to function at all...my guitars only draw power or need it when the sustainer is on. So, it can not be compared directly with commercial units and the point is mute...as are the statistics asked for. Besides, FF and others whatever the name they choose, don't have power to be even a factor in their criteria so what does that aspect even matter at all in that case?

If my designs have good battery life, it is simply a factor of requiring very little circuitry, only running when in use, no preamp gain and using the minimum possible gain to produce the effect. My later designs do use an LM386 but these things are adjustable in gain from 20-200x amplification...mine do sustain as did cols on even the lowest gain setting...on my tele I can run the LM386 to max...the range of "effect" changes, response and sound.

But there is nothing "magical" about the LM386, I have shown many alternate circuits that I have used and tested over the years. You could use two LM386's in BTL for instance on a very minimal gain and even less "circuitry" in many ways...or any number of other chips available should you choose. There are far more basic circuits "littering the internet" than there are driver designs and most are based on the simple one developed here or are evasive in the specifications making it difficult to replicate. That you seem to think you need a CNC machine to avoid "ugly" CD case bobbins...automatically takes such a proposal out of the average DIY territory...just as the jigs required to align the magnets in my hex designs left that out of contention with that criteria.

And in that quote, please note I am referring to my simple single coil driver and specifications...any design that significantly differs from this can work, but it is of course going to require developing the specifications. You could even change the specifications and develop circuitry to compensate, perhaps more power or whatever...I can only speak to having tried numerous variables with a basic theme and amplification that best suited the simplicity and practical nature requested for DIY construction at a time when I was developing far more complex hex designs and circuits beyond the DIY scope that people here were looking for. The proof is in the fact that it works and the independent verification of those replicating it...and to some extent the failures of those who have varied from it and got similar results (such as poor or no high string drive, distortion or squeal EMI effects, etc)

But really..."Iranian moderation style"...new here...well then, where have you been reading up on all this if not here at PG then?

[psw]

...since the goal of agc is to save power and energy. why don't create something that limit the use of power directly at the power source (+v) ? or the result is pretty much the same?

Yes...like a battery itself...that's a limited power source...or a driver so efficient at driving all the strings that you can turn the gain way down on the amp so it runs cleaner and less hard...

But really...the AGC is not there to save power but to even out the response and compensate in some cases drivers that have a high variance across different strings,,,

If considering potential AGC strategies though, cribbing audio processors limits your choices and benefits. Ideally you don't "hear" this 'amplifier' at all...it only functions to drive the string which have a physical momentum. Things that would be totally unacceptable in an audio processor ("pumping" or even intermittently turning off the entire amplifier to control gain) could well have big benefits in this application

The tests and discussion about distortion went on for a long time and the consensus really did fall pretty conclusively on the side of aiming to provide the driver with a clean-ish signal most like the physical vibrations of the physical string trying to be driven...

Really, the basic sustainer presented here and trying to be replicated by this thread and many like was envisioned as a fixed six string ebow and adheres to the principles of that device. An Ebow, if you check the patent, like this project states, uses any suitable "amplifier circuit known to the art"...in their case an LM386 and input and output coils impedance matched to the input and output of the amp. There is no AGC or even a buffer. In this project though, one has to at least match the high impedance guitar pickup to that of the circuit to prevent loading...this is a minimum requirement to make a "suitable" circuit in this application.

Now, if you want a different sound or you have a driver that has a different response characteristic you are going to need to compensate for that in the circuitry...however, as in this case, you design the driver to the application (a non-loading basic circuit and big enough to span all the string and fit on the guitar in a practical way)...it does work and the limits of the power it can draw on (the battery) or the power of the amp (small and adjusted for gain) it does in fact work...just like an ebow 'works'...

Of course, if like col whose criteria sought a very even response...you are going to want perhaps a more sophisticated AGC control to produce that effect. But, I did not seek to reproduce the sustainiac 'product' but use this technology to explore other options and sounds. For me, I like the dynamic sound, still controlled but that can play soft and loud and build and where the harmonics bloom and change with time and it is highly responsive to technique rather than automatically controlled by the circuitry...but that's my criteria...

There has never been any secret to that nor a judgment in it. All that matters really is for every individual you have a vision of what you are after and do the work required to achieve that...if you are after a very controlled even sustain you are going to want to go with more sophisticated circuitry....if you want or need to run it with a lot of power, you are likely to require a driver design (probably with multiple coils or some kind of magnetic shielding) so that you get drive without the EMI effects...

There is nothing "magical" about an LM386 at all as has been often repeated (any suitable amplifier circuit), and certainly if one hits the front end of the thing hard with excessive pre-amping...but that applies to any amp...it will distort, not increase the output...same with running it hard...I don't recall anyone who knows suggesting they run any of these things to their limits is advantageous. Without proper precautions it wont be stable, no amp can be. As I recall Col used an LM386 on the very lowest gain setting...20x when the LM386 is capable of running up to 200x..so you know...it can run clean enough at those kinds of powers and obviously also consume less power as well. But that isn't the 'reason' for it, he was looking for a particular controlled response and eliminating EMI effects and having to run more processing circuits.

But this thread was about a given design and strategy none of which features overt AGC or complex circuitry to work...it is and needs only be, simple...like an eBow...but one could take that basic project and tinker with it to your hearts content to get something that more closely matches your own personal criteria...

[big_boleros]

The lack of response to the above line of questioning is noteworthy.

Perhaps those who use the signature (elsewhere) "Mr DIY Sustainer" haven´t the answers for once?

[Prostheta]

Equally FF, pandering for moderator intervention on your behalf to solve your lack of civil two-way questioning ability is indicative of an abrasive attitude. Moderators can tolerate ignorance, just not stupidity that affects normal board congress. A+B=C doesn't apply if you are digging around for evidence of A whilst being unable to intelligently ask for B. Hence, no C....or more annoyingly C<>F².

My daddy said to me one time "if you can't say anything nice, don't say it at all".

If fact no, my daddy never say that ever. I think I read somebody else's son writing that elsewhere on the Interwebs. Whilst he was sat on his father's knee on his laptop, perhaps. But anyway.

[Joghurtgumi]

RESULTS! though still not quite perfect

I finally had enough, and simply hooked up the driver to my Behringer gm108 15 Watt amp, and when i cranked it up to full volume, and set it to overdrive, i finally got sustain at the 12th fret (if i held it in the neck pickup position i got terrible squealing noises from the driver) so the problems i can think of:

1: the amp i built is not strong enough (i doubt it, because i don't think other people are integrating 15 watt amps into their guitars.)

2: The driver is not right in some way

2/a: the magnet maybe? can it be too weak? how can i tell?(i don't have any measuring equipment except an old multimeter)

2/b: wrong sort of wire? (i don't think so, i ordered it especially for this purpose: 0.2 mm thickness)

the ohms on the driver are 8.3 ohms, and it's all potted, it has metal cores going through the coil.

the amp is the Fetzer-Ruby combination, i have tested it with a speaker, it works. I don't know how powerful it is, i don't know how to test it.

Please, could you tell me your opinions, on what you think the problem is, and how i might solve it?

[jaapie]

i'm trying to build a sort of Ebow Organ. I've got a single string prototype up and running, and i'm trying to figure out how to accomplish a few things. Primarily, I'm trying to figure out a non-mechanical way to stop the string from vibrating after the driver is turned off. Right now, my plan is to send a DC voltage to the driver. Theoretically i see no reason why this wouldn't work, and i've had success stopping the string by bringing a small rare-earth magnet near to it while it's vibrating. However, i haven't been able to do the same thing electromagnetically. The driver coil's resistance is around 7.5 ohms. Is this a workable solution? if so, how much current or voltage should i be sending through the coil (or at least, what would be a good starting point)?

[Prostheta]

Perhaps rather than trying to damp the string, reducing the electrical output of the pickup accordingly?

A hexaphonic pickup with seperately controlled outputs would be quite spectacular in concept.

I think that dampening a string electromagnetically would have the downside of inducing a corresponding signal in the pickups.

[psw]

I've helped many with the original design. This recent video showing a test in harmonic mode of a simple "blocked" stock single coil pickup (tele neck style) and using a 'Ruby' modded as suggested (not the F/R though that would work too) shows that the design is sound and works as one would expect.

Testing was done, first with a speaker to be sure the circuit is working as a low watt battery amp, then hooked to the guitar with a 'y' chord out of the output jack of a strat, one to the sustainer circuit, the other to a 'pignose' amp for testing. Testing well away from other pickups ensures there is no EMI problems, but I've found, once installed and with proper and complete bypass of all otehr pickups, it can work even better than the tests.

I've always suggested testing in this way before modifying the guitar in any way to ensure that the work on the project has been successful. If built as described and to high enough quality it will work very effectively. But, it is clearly not a project that suits everyone.

Hope that assists people who have, are or wish to experiement with such things.