ansil Posted June 6, 2004 Report Share Posted June 6, 2004 No way could you have read all that so fast!!!!! Ansil. psw actually yes.. i long since had to take multiple breaks from the diy forum as i read all the archives and all the links in three months and was making people angry by asking for more information and more websites.. Link to comment Share on other sites More sharing options...
psw Posted June 6, 2004 Author Report Share Posted June 6, 2004 Andreas It could really be as simple as that, I'm getting something happening. A few months back I got the brainwave of passing the string through the core of a coil. I mounted it behind a tune-o-matic bridge. It was pretty crude but I did get it to vibrate. I cant recall now if there even was a bridge pickup to work against. (It's dismantled now but it used to have a neck humbucker only). Come to think of it, I may have placed a small magnet under the string immediately after the bridge to work against. There were alot of ideas. I found a small prototype in the junk box which had a driving coil (wrapped around a steel rivet with iron powder in it's centre) and two magnets either side (N & S). The idea was that the string would be magnetised by the core and simultaneously attracted by one and repelled by the other from side to side. As I recall, that worked in a fashion just ahead of the bridge. I wasn't testing for radiation at that stage (it probably wasn't plugged in!) and was using the soundcard speakers with a software tone generator so it had heaps more power than you could get from a battery amp. The original test coil for what became CP5x (which was abandoned) used the same type of balancing act of the string being between the two poles of a sideways mag. (It has no string pull, so a very powerful magnet can be used!) Two coils were used to upset this balance and so vibrate the string. This also worked but was tricky to make (tiny coils) Anyway, the point is that you can drive the string from the bridge end, especially with a matching resonant frequency (I tuned the string to the tone generator so it operated only on it's fundumental). I really do think that there could be a way for the drive to come from stimulating the bridge magnetically (there is no mechanical vibration going on). Being metal it could make an ideal magnetic shield. There may even be some kind of physics at work here that I'm not familiar with. Perhaps the string vibrates because it is being stimulated magnetically at it's resonant frequency on some kind of molecular level? Purely speculating, as I have no idea! will type again soon psw P.S. A lesson for us all - don't let the kids near the computer - they killed my mouse - who needs a better mousetrap when there is a nine and a two year old in the house Link to comment Share on other sites More sharing options...
Biohazard Posted June 6, 2004 Report Share Posted June 6, 2004 This is amazing, i'm really enjoying reading this topic even though some of it is quite over my head. Good work. Link to comment Share on other sites More sharing options...
Andreas Posted June 6, 2004 Report Share Posted June 6, 2004 There may even be some kind of physics at work here that I'm not familiar with. Perhaps the string vibrates because it is being stimulated magnetically at it's resonant frequency on some kind of molecular level? Purely speculating, as I have no idea! Actually a current passing throught the string will create a magnetic field around it. That magnetic field will be driven by another magnetic field...pickups. I performed a test in my physics A level a while ago. I passed current throught a string that was the thickness of about the high E string. The current was driven by AC voltage so it had a certain frequency....I think it was 50Hz. Anyway...the experimend a magnet around the coil creating magnetic field around it (a pickup will do the same job). Then I started adding weights on the string...a way to tune it up. As soon as it started to match the frequency of the driving current it went wild. The current was kind of high and the magnetic field was strong. It had an amplitude of vibration of about 3 - 4 cm. So if this is aplied to guitar situation it can be thought that if the pickup output is passed throught the strings it will drive the strings instead of stoping them due to the magnetic pull. I will try to experiment on it on my strat copy and see what results I get. Link to comment Share on other sites More sharing options...
psw Posted June 7, 2004 Author Report Share Posted June 7, 2004 Great Andreas, I'd benefit from some co-experimentation. When I get some pictures up it will have better details so you can repeat and refine some of my experiments too... However...BE CAREFUL... AC currents can kill ! ! ! ! ! It's not simply a matter of voltage Magnetic fields though are relatively harmless and the static magnets require no energy themselves to run. AC currents are not something I'd fancy putting through the strings of a guitar though Im aware of the potential. The string acts as a single conductor as if in a coil and is not very efficient at all compared to layered conductors at creating magnetic fields. What it perfectly shows is the power of resonance. That is why the sustainer patents have complicated circuits to harness this efficiency by making allowances for phase differences etc. What you saw was that when the frequency of the power applied matched the frequency of the string (or was close enough to it) its response was dramatic. The problem is that electromagnets take time to establish it's field and to lose it. The result is that although it is intrinsically powered by the frequency of the string (it's generated from it afterall), This effect causes a 90 degree phase shift so that the maximum power is attained at the very point that the sound wave is turning negative. The amount of phase shift is also a product of frequency so it is not simply a matter of shifting everything with some kind of set delay (although a tiny delay altered according to frequeny would work - any ideas Ansil?) When there is more than one string being played there is a complicated signal for which only some portions are related to each string. A Hex pickup and driver system would address this, being effectively six Ebows. Currently I'm approaching the driver element by having a hex driver with each coil tuned to the frequencies typical of it's string. Effectively a crossover. This is a compromise but one that should work more efficiently and less complicated than current sustainers. Using tiny, but very powerful, localised magnetic fields, I'm hoping that this will provide alot of the "power" and small coils need only be used to upset the balance between the N & S poles. The issue of phase shift I hope to address by using series and parallel capacitors and resistors in addition to the inductor coils of the electromagnets. If anyone has some specialised knowledge of RCL circuits and how to configure the values needed, I'd love to hear from you...otherwise it's trial and error Of course the other issue is that anything that uses the pickups fields will cause a problem with interferance and also trigger unrelated resonances in the pickups themselves. Strong magnetic fields will also effect the sound of the guitar even when the sustainer is not in use unless very carefully contained. Simply running a signal through the string will cause feedback, but not necessarily in a manner desired to actually drive the string. More like Ansils Sustainer Mod which, unless my attempts were poor, creates this effect. (Perhaps you should call it a feedbacker mod, Ansil) Anyway, I'm delighted to here that your inspired to play around with these ideas in the real world. It's fascinating stuff to explore with strings and wires and even if the effect may not be quite what you were looking for you will be assured of an effect type you later psw Link to comment Share on other sites More sharing options...
psw Posted June 7, 2004 Author Report Share Posted June 7, 2004 Oh yeah, I'm reminded of this great idea that was put forward as a April fools joke in the UK Guitar Magazine - The Tickler. Programmed with a scale, it would give you an electric shock through the strings if you played a bum note. A very convincing review with photos and everything of the device. Another year they created a missing gibson design - The Thunderbolt - the rare 4th of the Explorer, Flying V and Moderne designs. It was a flying V, cut down the middle with the top half reversed making a pointed upper horn. So good that some forgeries appeared in the States shortly afterwards, one bought for a large sum by Rick Nielson from Cheap Trick! worth checking out their April editions Link to comment Share on other sites More sharing options...
ansil Posted June 8, 2004 Report Share Posted June 8, 2004 hmm well the final instalment of the synth backer is done i just need to get it in the computer and get it uploaded. ie its pen and paper right now. i decided to go ahead and put it through a bridge rectifier andget the upper ocatve out of it.. so that if you let it ring out for any longer than say three seconds it starts to go intothe rectifier. and get a hint of the upper harmonic. Link to comment Share on other sites More sharing options...
lovekraft Posted June 8, 2004 Report Share Posted June 8, 2004 That is why the sustainer patents have complicated circuits to harness this efficiency by making allowances for phase differences etc. Would you mind pointing out these complicated circuits that you speak of? Once again, the phase shift in an electromagnetic driver is a non-issue! Your pickups also induce some phase shift, and you can still get acoustic feedback, so the phase shift has a negligible effect on driving the string. The sustainer patents show a simple current amplifier driving an elctromagnetic transducer - since the Ebow obviously works, without any complicated phase compensation measures, there's no reason to become obsessive about a factor that has very little effect on the outcome (we call it "engineeurosis" 'round here). Take a look at the patent schematic: Fig. 4 Ansil, doesn't that look like a LM38X type power op-amp? All the other components are simply to limit bandwidth and gain to make the driver more efficient, not to compensate for any phase shift in the inductor. What you saw was that when the frequency of the power applied matched the frequency of the string (or was close enough to it) its response was dramatic. That's what you need to concentrate on - frequency, not phase. Unless the phase shift is almost exactly 180 degrees, the driver will "lock" phase with the string over a few cycles, just like a semiconductor PLL. Concentrate on making your driver circuit (and coil) more efficient - the rest will take care of itself. And , yes, running any AC current through the strings is a bad idea, and holds potential for grievous bodily harm!! Link to comment Share on other sites More sharing options...
ansil Posted June 8, 2004 Report Share Posted June 8, 2004 "Ansil, doesn't that look like a LM38X type power op-amp? All the other components are simply to limit bandwidth and gain to make the driver more efficient, not to compensate for any phase shift in the inductor." short answer yes.. it is a widely know fact on the other forum i play at that the sustainor does use a lm386 equivelant.. i am sorry i forgot to metnion this here. i feel like such a yutz.. also for something a little better input impeadance.. although i dont' know how much difference it would make here. try the lm380n-8 as it is an 8 pin version that is 700mw and has a 150k input impedance vs the lm386 50k. of course this is part of the charm of a 386 when used for dist. also questionwhat is the other symbol labeled 40 it looks like an inverter but without the inverter mark mani wish i could get the pics to work at the patent office.. i want to get that rockman sustainor schematic again. Link to comment Share on other sites More sharing options...
psw Posted June 8, 2004 Author Report Share Posted June 8, 2004 OK OK OK LK i'm sorry to get into this again...you may be right The basis of my drive circuit is a simple 386 amp with no added extras but an output cap and powered by a 9v (8.4v) rechargable battery. That seems to be the basis of the ebow as you point out. And I know the ebow works...so...why can I not repeat this with a proven coil (CP1) and a conventional guitar pickup separate from the guitars signal ??????????????? Reports on the internet of people who appear to have opened them up confirm this. I took what you have said on board and ignored this area for some time (fearing engeneeriosis) with some positive results and some interesting coil designs that do seem to increase efficiency, as I have documented. Early experiments showed that with enough power you can get it a string to vibrate by forcing it into phase with the driving signal. I found that not only was this power impractical, it pulled the string out of tune markedly and had very different responses to different frequencies. Acoustic feedback is related to phase shift. The angle and proximity of the guitar is crucial to achieving a reliable result. This compensates for phase shift via manipulating sound reflections, creating that minute delay required. Hence the amazing art of controling it in this manner. Look, I've got to go but I've found my 2" thick patent folder and will give you some numbers in the next couple of hours... psw Link to comment Share on other sites More sharing options...
Andreas Posted June 8, 2004 Report Share Posted June 8, 2004 Just something I would like to mention...I dont know if you already know this and it is completly useless for me to say it but the phase shift most probably will be of constant difference since we are talking about coherent sources...the delay is extremly small. Since the phase difference is constant it will create a stable driving pattern....it will just form a differend kind of vibration...hence the differend effect on differend frequencies. The phase difference if it is contant it will not cause in any way a dampening of the string. The dampening and amplification of the vibration only has to do with the frequency. Afterall a 0 phase difference is just a constant phase difference...thats why it works on a stable pattern of vibration. Link to comment Share on other sites More sharing options...
ansil Posted June 8, 2004 Report Share Posted June 8, 2004 hmm what about say two coils being driven from say a tda2822[yes i keep all these little chip no.s in my head lol] which essentially is like a dual lm386. but you set the gainw ith feedback ressistors.. set one up positive phase one up negative phase.. and use seomghitnl ike a 555timer to pulse the coils to create the nesecary back and forth movement via the switching of the two. and you could set the speed of the timer to effect the vibration i would say, that a slower speed would mean a longer time bettween charge and discharge and would also move more current sinceit had a longer cycle. and a smaller one would keep it moving more once it was in motion.. vibrating quicker. as the swing time would be less.. just a theroy.. though.. Link to comment Share on other sites More sharing options...
Andreas Posted June 8, 2004 Report Share Posted June 8, 2004 I may know physics but in electronics im a complete dumbass. I salute you ansil Link to comment Share on other sites More sharing options...
lovekraft Posted June 8, 2004 Report Share Posted June 8, 2004 Ansil, help me out here - didn't you (or one of your buds) use a low voltage relay coil to drive a string like a sustainer? Did a 386 give you enough power to do it? Did you have to address the phase shift issue? psw, I think maybe we're not communicating (a common problem for me) - if you can generate enough power, nothing else will matter. Try optimizing the flux of your coil by using a permanent magnet for the core (as in the Ebow/Fernandes) and using heavier wire so it'll handle more current. My two cents. Link to comment Share on other sites More sharing options...
ansil Posted June 9, 2004 Report Share Posted June 9, 2004 yes we have worked out about 90% of the bugs with our diy version of the ebow, but alas it was given up by me and a friend of mine. [he was like my sparing parter if i got stuck he would help me out, and vica versa] but he left the forum after a while and we all gave up on it cause the price of an ebow vs. the build price and batterie life trade offf we couldnt' figure otu how they did it.. in fact the ebow does have a permanent magnet and a coil of wire there driven by the lm386 equivelant. the 386 has mondo power for a chip that small it will drive 4*12 cabinet if you give it enough dc to work with. so yeah we never had a problem with it driving a coil.. we even used a lowvoltage darlington in previous expeirences. i never thought about the phase issues about it. i did find that sometimes if i put too much drive on it. i would cause the string to smack the fretboard and or the pickups.. but it was shortly after that i just stopped working on this due to time and space limitations in my old shop. i am going to try a newer version of my old design once i get into the new shop comepletely. Link to comment Share on other sites More sharing options...
darren wilson Posted June 9, 2004 Report Share Posted June 9, 2004 Well, if it's any consolation, the folks at Maniac Music/Sustainiac have been refining their driver and amp designs for about 10 years to get increased performance and efficiency. Rome wasn't built in a day! Link to comment Share on other sites More sharing options...
psw Posted June 10, 2004 Author Report Share Posted June 10, 2004 LINKS It’s been very neglectful and selfish of me to focus on my experiments and theories without referencing the basis of them. Especially since I promised links, etc. and haven’t posted any! – now that I’ve got a little bit of a handle on the controls – here goes... PATENTS For those interested but not checked them out yet patents and the secrets within can be accessed free at USPTO Patent Search You will need to download a viewer to see the actual original documents with diagrams The referenced by and cited by links will automatically send you to related patents so you can check out the origins of ideas and where they are going – much fun! Warning – you may soon start thinking in patent-speak and, like me, use a thousand words and still confuse the hell out of everybody!!!!! Now to sustainers... Here is a great little article on Michael Brooks Infinite Guitar and it’s heritage to the Sustainiac, Fernandes and Floyd Rose systems and a little of the secret workings of his! Infinite Guitar Article Ok, now... For Lovekraft, Ansil, et. al.... Perhaps the best for explaining the problem and lengths gone to by some to solving the phase shift dilemma (Heet’s Ebow not withstanding) is contained in Floyd Rose’s 1995 patent 5,233,123 Floyd Rose Sustainer Patent 1995 Because of the length of these documents I’ll spend the time to quote from them so that everybody need not wade through them as I did...so...from Floyd Rose page 7 = (FR7) Regarding phase shifts (FR7) The force applied by drive means employing an inductive coil tends to lag behind the drive signal or voltage applied to the coil. Moreover, this lag increases with the frequency of the signal. Details of the complex circuitry and formulas for lag and lead compensating (FR11-17) Ansil – (FR18) describes an alternative means by using a phototransistor which may be of interest to you. The phase shift circuitry involves (FR21) In operation, waveform squarer, frequency to voltage converter and amplifier cooperate to provide a signal voltage which increases directly with the predominant frequency of the pickup. Basically the f to v converter seems to switch in various capacitors with frequency Thus, as the capacitance of the drive decreases, the component of the drive force at a given frequency will have less lag (more lead) Another important patent is from Osbourne and Hoover 1999 (=OH) 5,932,827 This seems to relate to the Sustainiac Stealth System Sustainiac Stealth Website Osbourne and Hoover Sustainiac Patent 1999 This patent utilizes means to eliminate feedback (EMI shielding) and a means to conserve battery life. There is a description here of adverse effects of prior drivers on the tone of the guitar (OH17-18) For more on this subject, I found this discussion: Adverse Tone Effect Discussion Anyway, back to the phase shifts...(OH18) Means are also provided for enabling the driver to accept the phase inverted drive signal and provide a drive force that is generally in-phase with the vibration of the string On energy conservation (OH20) Provides a non-linear switching amplifier to decrease wasted energy On multi-string (one driver for all six) vs. single string (six individual drivers)...(OH26) Such an arrangement provides an advantage over a multi-string driver with respect to the direct magnetic feedback, but a disadvantage relative to the lateral uniformity of the magnetic field. On amplitude and frequency compensation (OH43) Current source amplifier automatically compensates the frequency related amplitude response and phase response of drive current OK, so there’s a smattering of the current state of play, except for the ubiquitous (just wanted to use that word) Ebow patent Ebow Patent Now, this is a lot to digest I know. I don’t have much experience in electronics (been teaching myself for this project) nor do I have a background in physics or the heavy-duty mathematics that I'm running into. What I hope to do is defeat this with guile, ingenuity, creativity and a lot of luck. ..oh and your contributions ....keep them up Hope this helps further our discussions psw Link to comment Share on other sites More sharing options...
darren wilson Posted June 10, 2004 Report Share Posted June 10, 2004 Good article on Michael Brook... not too many people have heard of him, but you've almost certainly heard the Infinite Guitar on U2 and Daniel Lanois recordings. I believe his "black box" is more than just an EQ... i believe it's an external amplifier used to drive enough current back to a standard pickup to drive the string. He's quite amazing to watch live... he manipulates loops in a most ingenious way. Link to comment Share on other sites More sharing options...
psw Posted June 10, 2004 Author Report Share Posted June 10, 2004 Now that took some doing and satisfies some for a while I'll just divert the subject... I'm hoping to add graphics to my posts (the colors aren't enough for me!) so lets try this... OK, so if that worked you should be able to access a jpeg (or will it just show up?) of the cross section of the CP5x coil design Yes it does work in a fashion In fact I was so enthused I went ahead and built a hex version with a wiring fault...well that wasted 2 days!!!!! Intrigued to know what you think... psw Link to comment Share on other sites More sharing options...
lovekraft Posted June 10, 2004 Report Share Posted June 10, 2004 OK, now I understand why you've been hung up on the phase issue - I just spent a couple of hours wading through some of the most obfuscated natural fertilizer that the best legal minds in the US can produce, and I'm probably, as the guy in Billy Madison said, "..dumber for having heard it...". Let me spend some time digesting it. It looks like a simple all-pass filter (the basic building block for a phase shifter) should take care of any real-world problems with phase lag (if they actually exist), but of course that wouldn't be patentable, since it would be reasonably obvious from prior art. The"non-linear square-wave amplifier" touted in Hoover is a Class D (or digital) power amp - it basically pulse-width modulates an ultrasonic signal at a fixed frequency above 40 KHz and passes the result through an integrator to retrieve an audio signal, much the way a one-bit Sigma Delta D/A converter does. Probably overkill for a DIY stab at this, but it could be made extremely efficient. At any rate, the one thing both patents seem to have in common are the basic signal chain: Pickup=>preamp=>current amp with gain control feedback=>driver coil(s) I think the trick is in the gain control - you'll need a compressor/limiter so as the string falls into phase lock and the input rises, the driver current is reduced to avoid overdriving the string itself and banging it into the frets. Simply clipping the pickup signal and then lowpassing it might give you enough gain reduction to bring it under control, or you may need active attenuation driven by the output signal. I'd be tempted to try a simple op-amp pre driving a diode clipper in front of one of Ansil's LM386 mini amps to push the driver coil, maybe with a phase reversal switch on the opamp's input, just to see how the simplest possible circuit would perform. OK, enough blathering - I'll try to find a simple phase compensation circuit (just for the sake of argument ), and report back. Oh, just one more question - if you're using a permanent magnet as a core, wouldn't it make better sense to orient the north and south poles vertically, since you're making a electromagnet rather than a pickup? Just a thought, and as always, I could be completely wrong about any/everything, so always check my math. BTW, dude, an excellent job on getting all that together and making it presentable - I know you put a lot of effort into it, and I for one appreciate it! Link to comment Share on other sites More sharing options...
ansil Posted June 10, 2004 Report Share Posted June 10, 2004 Now that took some doing and satisfies some for a while I'll just divert the subject... I'm hoping to add graphics to my posts (the colors aren't enough for me!) so lets try this... OK, so if that worked you should be able to access a jpeg (or will it just show up?) of the cross section of the CP5x coil design Yes it does work in a fashion In fact I was so enthused I went ahead and built a hex version with a wiring fault...well that wasted 2 days!!!!! Intrigued to know what you think... psw hmm thats similar to what i was doing although i used lead as a deflector instead of metal.. but mine wasn't as pretty as that one.. Link to comment Share on other sites More sharing options...
daveq Posted June 10, 2004 Report Share Posted June 10, 2004 psw - I read the first post again to try to understand better what you're attempting. You mentioned that sustainers don't work effectively. Can you explain what trouble you have been experiencing with them? What types of sustainers have you tried? I only have experience with the Sustainiac model C (the one that clamps on the headstock and actually vibrates the neck). It is incredible - very effective for my needs. Maybe it doesn't do what you are looking for so that's what I am trying to find out. Is there something about existing sustainers that you don't like or are you just having fun tinkering or ... ? It looks like you've done a ton of research on this - great work. I'd be very interested in seeing what you come up with. dave Link to comment Share on other sites More sharing options...
psw Posted June 10, 2004 Author Report Share Posted June 10, 2004 Oh No... I had this really good response last night but lost contact with the server and it appears to have gone...doh! The jist of it was that I keep coming around to LK's point of view. That I think that the resonant frequency of the coil may play a bigger role than the phase shift since then there's been a few more posts so briefly... Daveq I can't say that I have had access to any sustainers down here in oz. The model C was the first sustainer that I heard and was featured on a Guitar Player flexidisc and was incredibly impressed and got my balls rolling For those who dont know, the model C attaches to the headstock and uses a mains powered stomp box and the leaverage of the neck to kind of vibrate the whole instrument. I imagine the effect is a little like the trick of pushing the guitar head against the amps speaker baffle or cab to elicite feedback. It does involve a few extraneous wires, etc. It is the only system that allows you to patch effects into the drive signal...wayy cooll... which gets you into the natural synthersizer concepts I talked about. What I'm exploring is the more common electromagnetic drivers such as the sustaniac stealth system (see Links post above). These do have shortcomings...tone, battery life, predominace of notes over others, limitations o pickup choice, extensive modifications to the instrument... They have the advantage of being more an intregal part of the instrument and I like that idea...plus I like tinkering...and I don't like it when I can't get stuff to work...and I don't think it should be as complicated as the patents make out (witness the ebow)...and there's still alot of avenues left to explore. I really do believe that someone will take something like this, make some amazing music, and change the whole guitar scene...(oh Jimi, where art thee now in our hour of need) Ansil - CP5x uses metal to direct the power up and over the string. Measuring the strings position with my hall detector thingy, this is exactly neutral. This means no string pull, no dampening, no adverse tone effects and remarkable EMI control. The changing field is altomatically attracted to the opposing identical change in the other coil and the power of the magnet, which can be substantial can be added to because both poles are actively involved in moving the string. The motion of the string is indeed from side to side or circular like it would be naturally, not up and down which CP1 for instance did exclusively - less distortion and more control for the next step. Remember also that this thing is tiny 5x5x12mm. In fact, the deflector is made from common staples...now thats DIY ...there goes another secret Now youv'e let on that you have trided to replicate the ebow...tell me more I retried it with CP1 and realize now that I had the driving amp earthed to the guitar so it was not completely isolated as the ebow obviously is...still working on that. I seem to have some success driving a string with miniture ferrite inductors and that is where I'm heading at the moment...cheap...consistant...tiny...and I don't have to wind them . I still think there are merits to ferrite cores as they transmit but don't hold a permanent magnetism too well so should therefore be more responsive...or so i'm thinking Lovekraft...what can I say...I'm honoured . Don't back down though as you may indeed be the voice of reason! Andreas I know you're out there! With your physics background...what is the effect of vibrating a string from it's end (say bridge) on the propagation as the waves travel down the string...will it amplify, as in small waves become bigger? Obviously vibration is transmitted through the bridge to the instrument, what is the effect of the reverse? This may relate to the model C which vibrates from the nut end. Anyway...got to run...great stuff all psw Link to comment Share on other sites More sharing options...
lovekraft Posted June 10, 2004 Report Share Posted June 10, 2004 Lovekraft...what can I say...I'm honoured . Don't back down though as you may indeed be the voice of reason! No, don't misunderstand me, I still think the "phase issue" is smoke - but I understand after reading the patents why it worries you. However, this section from the FRS patent makes me think otherwise (and keep in mind that the full fundamental range of a 24-fret guitar in standard tuning is >80Hz to <1400Hz): With straight through circuit 78 engaged, the drive signal is in phase with the pickup signal, and hence the drive force lags behind the string motion by an amount equal to the lag caused by pickup 34 and driver 52. In this mode of operation the efficiency of the sustainer in reinforcing the fundamental vibration of the strings is less than with variable lead network 82 engaged. However, this effect is most pronounced at relatively high fundamental frequencies, above about 300 Hz and particularly above 600 Hz. Thus, the sustainer will provide a useful sustain action for relatively low frequency fundamentals when straight through circuit 78 is engaged. Moreover, when the straight through circuit is engaged, the sustainer does not tend to lock in on the frequency of only one string. It sounds like they're simply having to compensate for the inherent lowpass nature of the inductive driver and the fact that a shorter string takes more energy to drive it, but I still think it's a frequency response issue only peripherally related to phase shift. However, after wading through most of both of those patents, I'm convinced that the complicated systems described in each are just hedging their bets. I seriously doubt that either patent holder is implementing all of their "innovations" in the current incarnation of their commercial product - the rest is padding and hedging to make their claims look more innovative and therefore patentable (shades of Randall Smith!!). I'm convinced ( at least until someone proves me wrong ) that simple equalization just like that used to compensate a speaker (another inductive transducer) for flat response will more than take care of any problems that may result. Moreover, if you're using a separate driver for each string, you only have to make the response flat over a two octave range, further simplifying the necessary EQ. Digital amplifiers and frequency-dependent phase shift both sound good in marketing literature, but I'm not at all sure they add anything more than mystique to the final product. I would concentrate on gain control/compression and frequency response, designing a driver coil that works best as a driver (ie., don't try to use a pickup-style coil, think more along the lines of a diaphragm tweeter driver), and isolating the driver system electrically and magnetically from the signal path to avoid any timbral interaction. Of course, that's just my opinion - I could be completely wrong. Link to comment Share on other sites More sharing options...
psw Posted June 10, 2004 Author Report Share Posted June 10, 2004 LK...now we are on the same page This is exactly my thinking and in my lost reply, I detailed just such a system. With a hex driver, it should be looked at as a six way speaker system with each driver tailored specifically to the power and frequency requirements of the string it is trying to drive. I built such a system but am having trouble getting the details right...more later Now, for something real stupid... I thought, what the hell, I'll just wind a driving coil around a single coil ith some steel wire between, running completely separate from the instrument. Turns it into a transformer...got the same result that you would get putting a transformer near a guitar...terrible hum from about two feet away... Well, perhaps that was a little too nieve...time to get cleaver again cheers psw Link to comment Share on other sites More sharing options...
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