Hank McSpank

Good post. I can say quite categorically here & now (& without any sense of embarrsment or shame!)...if I *ever* do get a hex driver working, then without a shadow doubt there will be six LEDs aboard the final driver. design..you can *never* have enough guitar bling!

I guess I was tripped by space's associated comment... ...he then went on to do some detective work resulting in the schematic he posted. space, could you go to the final frontier & clarify which schematic you posted a couple of pages back please?

(oops double post - can't find a delete post buttong either?) Space_ryson....tks for ID'ing Q8/9 ...I'm not familair with that variant. Also, since this is a push/pull power amp, I'd have expected the transistors to have had slightly different numbers? (one will be a PNP...eg MJE172 & the other NPN such as a MJE182)

I'd have to say, if my main flagship product was destined to go in a guitar as the Fernandes system is, I think I'd be able to model it in a fashion that it doesn't look like it was desgned/built in 1952! Haven't they ever hear of SMD & small Molex headers?! Ubelievable. Incidentally, have we seen the Fernandes schematic pass through these parts in the past 300 pages? That sustainer circuit the other day (Floyd Rose?), was really interesting...more please!

Post edited/appended - - see footnote: Something quite noteable happened this afternoon. While messing about with scores of permutatiions (driver position, VCC voltage level, signal 'drive' level, driver orientation, height from string etc) with my single sting driver (yes, still on that for now!), I established that under certain conditions, the driver can be anywhere between the bridge & middle pickup with *NO* EMI whatsoever (nada, nothing...guitar output clean as a whistle)...in fact only when I move the driver *directly* over the bridge pickup pole pieces do I then get squeal. this is quite interesting as obviously it means such a driver could be mounted wherever you want on the guitar without having to worry about EMI! (it's early days yet though...perhaps when I add more drivers into the equation such a 'win' will disappear) One other thing I've noticed, when the single string driver is positioned on the G string (& adjusted just at the 'edge of sustain' ...just to make the G sting excite nicely)....it has enough 'reach' to excite the D & the A strings too! (I'd video these scenarios for you all to see, but I've only got a simple point & shoot camera & you wouldn't be able to hear the clarity of the guitar's output - fed into a small amp I knocked up & listened to through headphones) These two observations are quite a revelation to me at least (especially in relation to my first night's testing when I could get rid of EMI with a sig gen input even at a couple of metres from the pickup!) Anyway, it's into the loft (it's after 10.00pm, so again I won't get much done tonight!) Footnote: All sorts of problems tonight (I have a bench tri-PSU, but it whacks out a fair amount of EMI itself, so I knocked up a simple little 7V regulated DC power supply ciruit, but had no ends of problems) IMHO, single string drivers are proving to be *very* handy for honing in on specific areas of Sustain-age! (if you can make one, I encourage you to do so). It's now quite clear that's it's entirely possible to make small coil sustainer & place it anywhere on the guitar & not worry about EMI ...the catch? Only the bottom 4 strings will be squeal free! On the low E through G stings, pure sustain, no fizz, no EMI...next to any pickup you care to place the driver (of course this is only a one string driver & these obs may be negated when a coiuple more are added into the mix, but like I said earlier, this one string driver has some reach!). When the EMI comes into the equation, is when trying to sustain the top two strings...those two strings need significantly more drive (well, for this 8 Ohm coil with 400 windings of 0.15mm at least). This 'extra' drive get's whacked out as fierce EMI...serious amounts of EMI. Quite remarkable really...bottom 4 strings = very little drive needed...very *very* clean sustain signal (& it'll sustain until Kingdom Come)....but sigh, I guess most folks want six strings?!! (sustainers, schmustainers). Ok, now to to Cols earlier points... Agreed. I'm not even sure how the TDA7053A appeared on the radar here - the mono variant (7052A) you mention is the one to go for. There's a couple of othe manafacturer's mono variants too (ie with DC volume control)....an LM4865 and TEA7530. >>near 180º phase - I don't know, I'd need to scope the input & output (had too many probs to get deep down & dirty with this one) >>there is a significant DC current through the driver a quick current check revealed nothing untoward. >>some sort of parasitic oscillation is causing a choking effect on the string when the gain is increased Nope...signal across the coil is is clean (just how have you guys got as far as you have without visibility of the output signal?!) So I've still not fully accounted for the high E & B string 'choking'... & there's invisible stuff here that I can't easily quantify (permananet & elecro-magnetic fields!). My theory is that it's the higher frequencies (top E & B string) fighting against the inductance of the coil, coupled with *possibly* the TDA7053A not having enough firepower for this condition. I now need to make a single coil driver with less windings (need thinner wire) Yes, & it's proving a revelation wrt revealing things like the best 'excitation points' along each string. As an aside, if you hold the single string driver over an existing pickup...the string is strangled completely (moog guitar anyone?) Yes, I'm sure the coil hasn't been flipped (I have the driver in a holder and simply move the holder across a little above each string in turn) I'm testing everywhere...like I say, the 4 lowest strings will sustain anywhere on the fretboard (open though highest fret) I'm using the guitar not a sig gen (a cheap strat with single coil pickup...I'm figuring if I can get this to sustain EMI free, every other guitar will be a doddle!) - I will revisit the sig gen thoughas input though (if for no other reason ...just to get a handle on why so much EMI) none of that made much sense...off to Google! BTW: Your idea of using a chip like the SSM2166 for the AGC/preamp is a good 'un, but it's pin count is just too high if I was going the hex route (& I'd need six of them at £5.00 each !) There'll not be much updates from me for a day or two, as some parts have now arrived for another project I've on the go ...a homemade CNC, which will really help my sustainer project a little further down the line (eg cutting a custom 6 x 'single string' driver holder from black 3mm acrylic), so over the next day or two, I'll be cracking on with that....... [everyone breathes a sigh of relief]

Since you're referring to me - just one point of order (& just what is it with you, we're never more than a post or two away from contention) ...when I said "it matters not a tot", you need to put it into the context ...ie at that particular time, I was collecting technical data (specifically about power levels to drive each string at different points along the fretboard)...in this instance, the EMI on the guitar output (that you're relating my quote to) did not "matter a tot" - that doesn't mean I think the issue is insignificant....I just feel it's insignificant when measuring power levels. To use my boat analogy ...I'm stress testing to see if the engine is up to the job ...sure, there may be a hulking great whole in the hull ...but at this point 'it matters not a tot' ....I'll get to it - you can be sure I won't I won't put the boat out out to sea until I do. [Hank retires to the poopdeck to ponder how this analogy might be twisted] I'm aware of all the hurdles, but I can't tackle them all in the first few nights of testing ...hence my "I'll tackle that later" quip. You're very quick to jump in prematurely, steering my early findings in such a way that you prop up the bar at the "The Sustainer Arms" & spout off to the new customers (whether they want to hear or not!) - but relax, I will get to each of these hurdles in turn ....we can discuss/debate those particular points when I do. I've covered a lot of ground in a short time - I'm already & starting to hone in on some possible circuit 'solutions', but give me a break! (remember, I'm only about 4 nights into this project & @2.5hrs per night - that's just over one man day...I've got a few years 'breathing space ahead') Not much more to report on the experiments today...I did a little bit more testing earlier this evening, which revealed the TDA7053A (the 'A' here is important - it's the variant with two DC Volume control pins) to be quite a capable power amp chip (Col you might want to hold off building that push/pull output stage - unless you've decided to go that firmly route anyway of course - & would you believe I only went & bought some TIP122/127s trannies this afternoon - doh!). Anyway, with the TDA7053A, I adopted the role of a 'Hank AGC' & tweaked the DC Volume control to the chip while moving between strings & in differnt fretboard position - it worked brilliantly on the Low E to G strings (at all fretboard positions). I saw some HF ripple sumperimposed on the signal as scoped across the driver, but it's worthing noting that my workbench is not a particularly scope friendly enviroment & the HF could be coming from the fluorescent bench lamp, my soldering iron, sig gen RF artefacts etc. The high E & B string proved to be very hard to coax into excitation...& weirdly, cranking up the TDA7053 volume control actually choked the plucked string (& this is with the driver orientated the same way as when exciting all the other just fine)...there's definitely something unique about these two particular strings that'll need a lot more investigation...my gut feeling is that it'll likely need a bespoke driver &/or circuit dedicated just to those two strings (I'm thinking a coil with less impedance, therefore less turns of wire...which obviously takes the DC resistance down...I need to see what i can get away with wrt the TDA7053 in this instance)

You may be right, but I've got the stuff in my hands (whereas I haven't any 0.2mm or 0.31mm)...from my one string test, the amount of power needed to drive a single string is remarkably low...it'd be interesting to see how the power requirements scale up. Yeah, but I'm a bloke in an uncoverted loft with a few spare components, a scope, a DVM & about a day's PIC programming experience .....in other words at this stage in the game, any 6 channel PIC system &/or SMD is totally out the question! (as I'd imagine it is for most of those passing through this thread ...so I'd not listed it as an option!)

Well, the TDA7248 has been struck off my list (it's lying in the bin next to it's new buddy ...an LM386!) ...it's *awful* ....when feeding it a pure sine wave via a small Opamp based preamp (TL074) - the sine wave is clean as a whistle out of the TL074 ...it then it feeds into the TDA7248...it comes out of that awful, just awful. End result? (when used with a sustainer & fed with a guitar signal). Fizz & distortion (nicely controlled at that though!) Folks, we're going to need a proper AGC circuit** that yields an output that's as pure as the driven snow...and definitely a threshold circuit too (because the AGC simply will simply try to amplify the background noise when your playing softly...which ends up with a very messy signal being fed to the driver) & I'm now figuring that any such 'proper' circuit it will need too many discreet components to make 6 channels (hex) viable. Therefore at this relatively early stage, it's looking like Hex may have to be 'parked' (& before Pete has a 'told you so' fit...it's not because of the driver...it's down to the high component count likely needed just to get a nice clean signal for *one* channel!). If I can nail a good end to end circuit for one channel, this circuit might scale up to hex using SMT. My 'parking' doesn't mean aborting (it's still the end goal, but I need to see physically small a one channel circuit can be made) And Pete - that doesn't mean I'm going to copy your driver...far from it! I've heard you say on many occasion it must be 0.2mm wire ...well, I have a load of 0.15mm lying around & look forward to proving it needn't be 0.2mm ;-) I'll also be developing my own circuit...as the LM386 is truly terrible (BTW: I don't think it's a valid argument to say the LM386 is a good solution because it's cheap ...here in the UK an LM386 costs about 50p, but a proper class B output power amp is only likely to be £2!) I like your line of thinking...(I've not had time to read the datasheet...but I will read it later, & will have a bit of a Google too), after just a few hours of 'sustainer experimenting', it's quite clear that there's not a whole lot of options here ..... Have a low tech 'budget' sustainer (with possible distortion & fizz) Have a rolls royce sustainer (no fizz, even sustain but high component count...therefore probably a chunky cct board) Some hybrid(!) solution - ie going discreet component where no ready IC solution exists, but utilising suitable ICs where we can (the absolute goal .....pure sine wave in = sine wave out ...if this scenario, we can ultimatley feed a guitar signal through the circuit without fear of fizz. Oh dear, I'm going to have to wind myself a larger six string driver now! **Edit: Just cleaned up most of the obvious the bad grammar & typos (that'll be speed typing for you!) I'm just pondering this a little more - perhaps what we need is more of a limiting circuit rather than an AGC circuit - the power amp & driver are essentially a gain circuit - if we limit/control that gain (by limiting the guitar signal fed back into the the power amp), well we've got an AGC by proxy! The signal into our sustainer circuit will always be quite chunky in the great scheme of things & the AGC just raises the moise floor - we might be able to dispense with the threshold if we don't use AGC?

My only objection to using that chip and others like it is that it's obsolete, so it will get harder and harder to find. Col Agreed, it wasn't so easy to source (but I only needed a couple)...are there an other alternatives? Using such a device obviously keeps the component count (& complexity) low ..After posting, I gave it another 15 mins & did get the chip to work using a sig gen as an input (proving my theory, it's no good for direct connection to a mag pickup),....one alarming aspect is that it really did markedly as some distortion on to the sine wave as seen on the output (again it was late & I might have slipped up)

Aaah, I just revisited your post... there wasn't enough detail! - but in series makes complete sense now! My only thought here is that we're trying to fight EMF that was created using 200+ turns on the main driver - is a simple one or two turn reversed loop up to the job? (also, it's not exactly the most concise, aesthetically pleasing solution ... but nevertheless worth spending a short while toying with) I've had a totally frustrating night dicking about with a chip with AGC built into it (a TDA7284 - another one of zfrittz6's circuits...I do rate some of the stuff he came up & I'd like to eliminate them from my enquiries first) ...I can't get a peep out of it when I feed it a guitar signal. I now suspect it needs a a buffer opamp between the guitar output & its input (it's actually meant for a tape recorder AGC....the datasheet is awful...also, I feel I should be wearing big flares, with massive hair & listening to music by Howard Jones as I construct the lash up). It's the most embarrasingly simple of circuits too... http://www.ea4nh.com/articulos/alc/fig06.htm....some Google-ated translation splurge about the chip from a user too... http://www.tinyurl.com/c5azq7 hey ho.

I should quantify... I can locate 0.2Rs but only in larger wirewound 3-5W varieties (Farnell have some in 0.5W, which are SMT, but since they'll be bigger than normal, they're likely to be useable) Re the blocking coil (or active shield, if we want to go all Trekky!)....it's not clear what's being fed into the bell wire? what you've decribed would obviously have a very low DC resistance & therefore pull a whacking amount of current! Also was there any inverse driver signal being channeled into it? Thanks for the heads up wrt placing cores between hex coils...I'm still a way off observing how several hex coils interact yet, as I'm still dicking about trying to get the approximate 'starter for 10' coil (I'm hoping to get the windings down to something in the order of 150, as it's seems the 0.15mm wire at 400 turns on my bobbin - to make 8 ohms - results in a coil to 'perky' for its purpose)....smaller seems to be the name of the game here - & not easy to get bobbins for what I'm intending doing. (* my previous attempts at winding have illustrated all too clearly that some form of bobbin is needed to wind a coil!)

Like most things in life, there'll not be one simple solution...but likely a combination - a hybrid outcome. Putting out power only when it's needed is good (& I raised this point after the sustainer circuit was posted up yesterday), but I'd say that applying only the bare the miniimum of power and only when it's needed is even better - see .....a hybrid in it's embryonic stages! This is why I'm more focused on getting some meaningful data down (power required per driver, per string etc). I tried sourcing some 0.2R resistors today (to no avail!), as I do think a constant current through the driver coil approach is a better than trying to compensate voltage vs frequency using filters earlier in the circuit...hey ho, the hunt continues. PS Re reversing the signal to the coils (for harmonics) ...well, I'm on breadboard & at this stage don't have a switch in cct (& being late, couldn't be bothered to reverse the wires manually!) - I did notice that when I flipped the driver coil a full 180°, the bridge output squealed like a good pig with a septic trotter. Harmonic switches are way further down the line (& 'if at all' - as my approach to harmonics will likely take a different tack). I actually seek clean fundamental frequency sustain evenly applied across all the strings over all else. ....especially in these early stages. PPS I'm not presently geared up to make your standard issue prescribed driver on my pickup winder - yet. My traversal system feeds copper wire onto metal rod held/turned by a drill chuck holding arrangment. I'll need to make a bobbin holder to go into that holder (which I will do soon, as it gives me more options)

Hmm...I'm not convinced that any of those should dissuade further investigation (yet!) Re needing power... the EMI 'level' obviously drops off as the distance from the driver increases...therefore it shouldn't need as much current (in comparison to the power in the driver coil - which isn't that much anyway!) Re the blocking coil putting out it's own EMI ...well, that's the whole point!. If you get the balance/ratios right, the EMI eminating from the driver should exactly be cancelled by the blocking coil. RE 'cancelling forces in the driver', again, the blocking coil should be at such a low EMF level (& sufficient distance from the driver) not to figure in this equation. Since there hasn't been that much exploration down this avenue, I'll put this one for the 'to try' soon list. (btw, I can prove/disprove zfrittz6 switching solution sometime over the weekend hopefully) Please, you need to gather some facts before you start finding 'flaws'. My intention (at this stage - until proved otherwise) is never to have the sustainer driver active when the the neck or middle pickup are selected ...hence the driver's position relative to the neck/middle pickup matters not a tot ...what does matter of course, is the driver's position wrt to the bridge pickup....but last night I established that the EMI is sufficiently low up until about 1cm from the middle pickup...at this point squeal from the bridge pickups erupts (as it goes, that video is out of date...the neck pickup was taken out of the guitar early last night & the 0.063mm wire peeled off the pickup pending further driver coil experiments!)

Hmm...convinced that any of those should dissuade (yet!) Re needing power... the EMI 'level' obviously drops off as the distance from the driver increases...therefore it shouldn't need as much current (in comparison to the power in the driver coil - which isn't that much anyway!) Re the blocking coil putting out it's own EMI ...well, that's the whole point!. If you get the balance/ratios right, the EMI eminating from the driver should exactly be cancelled by the blocking coil. RE 'cancelling forces in the driver', again, the blocking coil should be at such a low EMF level (& sufficient distance from the driver) not to figure in this equation. Since there hasn't been that much exploration down this avenue, I'll put this one for the 'to try' soon list. (btw, I can prove/disprove zfrittz6 switching solution sometime over the weekend hopefully)

Just a thought...in the previous 300 pages, has anyone experimented with 'Y'-ing off the power amp input signal ....& then feeding this duplicate signal 'inverted' to a say a 'blocker' coil placed somewhere between the driver & the middle guitar pickup? (& at a slightly lower level towards cancelling the EMI)

We need 'MAN' terms here ....eg inductance, resonance, distortion, EMF, EMI, flux ..........but 'fizz'? (I'm jesting here....ok?!) It is if you've got [dons a skirt] 'fizz' & you can't figure out where it's coming from! [parks girlie 'fizz' jokes for the foreseeable future] Yes it is....and it has storage capability too (handy for transiential sounds like guitar strings) - but have you ever scoped a guitar magnetic pickup signal? It's very small & certainly on the scope, not all that 'clean' to look at. I'm fairly convinced that fizz is reasonably easy to identify across the driver...to replicate I cranked VCC both up and down & could hear it on the guitar output - for the fizz I'v heard, the signal across the driver either visually clips or changes it's attack/release element (when VCC drops below the chip's normal operating range) They're all plausible, but it the light that I have no fizz when the VCC is set for correctly for a decent output stage (ie not an LM386!), then we can probably place less significance on a good few of those. The wind does seem to be quite blustery. Completely agree...rather than try & work it out on paper, I'm just gonna have to suck it and see... & yes, wasn't my auto coil winding machine was visionary?! lol !!

My reason for going 'non real world' initially, was purely to get a controlled enviroment. I'm actually quite shocked at the night & day results. ...I certainly cant account for why feeding a standalone sine wave into the driver vs the guitar string (which very soon morphs into a sine wave anyway!) should yield *massively* different amounts of EMI. I'd really like to be able to explain that one away! Non patronising tone gratefully accepted! I'm viewing it the other way...once I have all drivers in place, each 'tuned' for minimum current...there ought to be less 'reach'/sprawl of EMI. Yes, there'll certainly be more EMI activity in the immediate vicinity of the driver...but like I say...I'm hoping its reach will be less. This could be the one massive kick in the pants...all this work I then eventually assemble it together down the line only to find & it's EMI Central! to be truthful...what I got was a false negative...the sig gen was much *much* worse (like 100 times) than using the guitar signal as an input (& who'd have thought?!) It was so bad, I was genuinely puzzled how anyone could have a working sustainer without EMI! I was getting EMI with the mini driver located up at the machine head lol. This is troubling me, but I haven't got time to investigate this right now ( I've only so many CPU cycles in my head I can dedicate to the issue-ettes this project throws up!). If you get a minute & want to have your head messed up, download test tone generator...plug the output of your soundcard into your driver circuit's input...prepare to don radioactive underpants due to the shear amount of EMI bounding about!

but that wouldn't be the case when the battery is dying (when youve said fizz is especially prevelant) You get fizz when there's hard clipping. This occurs with too much gain. It also occurs when the battery is very low - As the battery drains, the voltage drops and the headroom is reduced so clipping occurs with lower voltage signals than when the battery is fresh. cheers Col I'd say that fizz could possibly be better defined as distortion as seen on the signal across the driver vs the input signal .....this could be either Hard clipping (driving the output signal past VCC) or soft clipping (VCC is fading away below that of output stage's normal working 'region)....OR any other other form of interference on the driver signal. In short it's distortion...but even though fizz seems a bit of a girlie description...it's very apt! Re the 330hz - a different tack tonight ...& a whole different ballgame...no matter how I tried last night (using a sig gen as an input), I could not rid the guitar output of the most dreadful EMI (just an overpowering sound of the sig gen's frequency). Out of desperation, I quickly knocked up a TL072 based preamp...fed my guitar bridge pickup into that...then onwards to a TDA7053A (stereo amp with DC volume control).....sustain was sweet, with EMI relatively easy to eliminate. The outputon the scope was as pure as the driven snow too...none of the ugliness of the LM386. I want to revisit the sig gen approach, as it's the best way of control conditions, but for now, I need to crack on & start taking some reading. Sadly, I ran out of time again...but with my 8 ohm single coil, driving the Low E, A, D, G strings was very easy - the B String was troublesome, the high E just about do-able. This is a conundrum...why should the B string be such a problem (it's thicker than the high E...& the high E sustains - anyway needs further pondering! Tonights obs... 5V-6V seems fine as VCC ...certainly into 8 ohms at least...though I intend knocking up a variety of coils with different impedances to test (I had my missus peeling an old pickup tonight to get me enough 0.063mm wire!) The TDA7053A seems viable - I like its elegant DC volume control, which could be ganged to control all 3 ICs needed for 6 strings (ie for sustainer intensity), there's also no visible distortion on the scope trace - but being two channels, it's not really an obvious choice for the single driver clan though! I'm noticing that a fundamental frequency is easier to 'excite' with the driver near the middle pickup location (I can get about 1.5cm from the edge of the middle pickup, before squeal becomes a factor)...the harmonic is the most predominant 'excitable' frequency between the neck & the neck pickup (but I'm sure you all already knew this!) One quick number, for this 8 ohm coil (400 turns of 0.15mm ...1cm deep, core of 5mm mild steel), there's 300mV peak to peak needed for the G string to 'sustain' just past what I call 'the edge' (about 25mA AC current measured with my DVM). This figure tails away as the strings get thicker (eg the A String at the 12th fret needed approximately 180mV & 15mA This last point is where I personally think a major win of the hex approach lays....tailored coils (& current) per string. I also very much like the idea, of having tailored the coils to each string, a circuit which will yield a constant current into the coil. I could be wrong (& I'm sure Pete will chime in that he's already tried & the reusults weren't good), but I'm hoping with the right 'tailored' coil per string, coupled with the absolute minimal but constant amount of current needed to get the string sustaining *just* past the 'edge', that inter string driver interference will not be a major source of problems. Imagine each strings driver wielding supreme control of its own string...strum a chord & hold...no dominant string...bliss. Anyway, bed beckons.

Perhaps it's my terminology - I mean definable/controlled harmonics on demand. eg "I want a fifth harmonic?" seventh harmonic etc? At the minute, you can get the fundamental, octave (& fifth?) quite easy - flick a switch & wait for it to arrive'...but it's not exaclty controlled (vs fading in/out a desired harmonic with say a footpedal)...that's what I mean by 'on demand'. Well, if we're all to row together in the same direction...we need to agree a common name for each bad by-product, agree it's cause & then we can work towards treating it. I don't think it's good to simply bundle fizz in with 'general EMI' it' might be getting into the guitar signal via EMI, but it s derivative thereof...if we know what's causing it, we can 'handle' it. I'd already noticed that there's more fizz below 5V, a different type of fizz above 9V - this fizz can be heard in amongst the other more predominant EMI. Yes, but other than a general observation that the fizz creeps in more as the battery fades...what's the technical explanation? but that wouldn't be the case when the battery is dying (when youve said fizz is especially prevelant) I'd noticed the string 'excites' way differently to the way a string moves when it's plucked - this does indeed yield a different timbre. Well, there's now one less LM386 in operational use - it's been retired in this household for the foreseeable future...I may come back to it after I've carried out some experiments with dual rails output stages, but for now....it's filed under "euuuugh".

:-) nice to have your input. The negative feedback is indeed a clever 'workaround' I'd overlooked wrt to the crossover distortion (I was focusing on the 0V DC at the emitters under quiescent conditions - which is another important purpose the negative feedback fulfills - I've since ripped that crossover part out of my post, as like I say, bad info is worse than no info!). I'd love spend some time & get a handle on that SPICE sim - is it intuitive to use?

I'm not sure I understand what you're getting at. Their solution is essentially a string driver...it needs an input (ie there is no pickup circuitry in their device). This is why they're saying their device must be connected 'first in the chain' of effects ...so they can send the unadulterated guitar signal to their driver coil to stimulate the strings. It really is a very clever workaround/solution to all the nasty by-products that sustainers have. Crayon indeed! The DC resistance of the driver is only 9.8 ohms! How do I test inductance? I'm not taking the driver apart, since I don't want to jeopardize it working, but there is some info on windings, etc. in patent 5,123,324. In a prior post in this thread I took shots of both sides of the circuit board, which may be of some help Excellent...just found it http://www.tinyurl.com/clbrhu (I can see they've used a TL074 for U1 & a TL064 for U2)...I can't make out the power transistors Q9 & Q10 though (it'd be helpful if you could eyeball their casings to see what characters they have on them) Since the transformer doesn't work now anyway, if push comes to shove, you could always desolder it & on the damaged side start unwinding it (presumably one side's coil is reading open/short circuit), - keeping a count of the number of windings get a micrometer to establish the wire gauge ....once you have the number of windings & the gauge info to hand - rewind it with replacement wire! Don't laugh, my wife used to do this for a living...& it's as low tech as that!

Thanks for that David....I'd never heard of the system. Their approach is quite innovative. I joked just yesterday that what's really needed is a way of moving the 'point of sustain' (tracks & rails on the guitar!)...but that's essentially what they're doing (albeit the guitar is doing the moving!). Also with mounting it off the guitar, it eliminates 80% of the problems....phantom power, EMI, the guitarist get to keep the original pickups etc. It's a great implementation & a bit of a slam dunk for the competition methinks (though the price is a bit chunky!) I see they're also releasing a harminic footswitch in May. No doubt this will allow the guitarist to select which 'harmonic' he wants to fade in (something I'm hoping to be implementing along the line)...this is quite revolutionary as sustain with "on demand harmonics" are the holy grail ...yet are bit of a lottery at the moment!

That's a great little schematic (but it looks like it was drawn by someone with a crayon!). I'd love to have had some readings for the associated driver coil ...inductcance, DC resistance, wire gauge etc. (DC resistance would be a start....do you have a way of measuring this space_ryerson) Ok, here's my take -the transformer 'T1' is *only* used to crank up the driver coil signal level it can also be utilised as a traditional magnetic pickup - it's not used in the sustaining aspect of the circuit at all. Therefore if you're saying your sustainer doesn't work because of transformer 'T1' being faulty - then T1 is *not* your problem...ie you have a fault elsewhere. If you're saying your system doesn't work with the driver being used as a traditional guitar pickup coil...then yes, space_ryerson, you'll need a 25:1 step up transformer (that said, if it's also not sustaining too, it'll likely be be the driver coil - have you have done a DC resisiatnce check?). Here's how I interpret it *roughly* - The normal guitar signal comes in from the bridge pickup, it is then buffered/split by a high input impedance/low output impedance unity gain circuit (Q3)...the original bridge pickup signal is then fed out of the 'out' leg.... the signal to be fed to the driver coil, then start's it's journey up into U1A. They've used a lot of components, but essentially here's the chain.... bridge pickup -> unity gain (non inverting) buffer -> non inverting preamp (though the phase compensation looks a bit lightweight) -> driver signal 'strength' & AGC circuit -> harmonic mode switch (ie reverse polarity of signal feeding driver) -> Class B push/pull power amp -> driver coil. (BTW: the 'busy' switching going on around S1, is just because they have so many permutations (eg coil 34....can be used as a sustain/driver coil or traditional pickup coil) - we don't need anywhere near as many switching permutations! In fact S1 can all but be eliminated for our basic sustainer (we just need a power switch & harmonic switch) Some observations They use dual rail ...something which after my experiments last night, I'm now beginning to lean towards myself (I think it's pretty essential to have 0V DC on the +ve driver connection in the absence of an input signal...this isn't the case with an LM386 output, therefore blocking cap needed - bit it's better to have 0V there in the first place) They use a bit of 'threshold' circuitry, both to conserve power & stop EMI when the bridge pickup input signal falls below a preset level (makes complete sense & I've not seen much reference to that aspect on here) Probably the most significant part of the design for me, is the fact they've used dual rail with a Class B push/pull design for the power amp. Also, it's worth noting they've not gone overboard with trying to lock the phase of the input signal with the driver signal. A lot of their circuitry is bordering on overkill for hobbyists & can be removed for replica test purpose. For example...do we really need a battery indicator?!(it's useful, but not essential...when the sustained signal goes weak/feeble...change the battery!) Also, in a workshop enviroment - if, like me, you have a dual rail bench PSU - you can obviously bin the bits in the top left - & if you don't want to utilise the sustainer driver as a pickup, you can bin T1 & all its associated connections (inc the S1 aspect)! space_ryerson - is there any chance you could note down what characters the following components have on their casing... Chip U1 (it's a quad opamp...just like to know which variant they used) Chip U2 (ditto) Transistors Q9 & Q10 I'm still not totally clear what the battery connections are (it looks like two batteries are being used - 2 x 9V PP9s?)...VCC is the positive rail & VEE is the negative rail. Well, after a further night's experimentation, I'm starting to really hate that LM386...it truly is a pig of a little chip. It distorts the signal terribly (which I reckon accounts for the 'fizz' many speak of on here). I've revisted & edited my test results from two nights ago (specifically about disregarding distortion - bad info is worse than no info!). I did use a TDA7053A power amp chip to drive the coil ...the output was *much*, much better as observed on a scope...but ran out of time. By the way, it'd be nice to have us all the same language, so here's my take (& once agreed it should be in a FAQ) EMI = Electro-Magnetic Interference (audible hum induced into the bridge pickup from the sustain driver magnetic field - same frequency as the signal being applied to the driver ) Fizz = Audible distortion (sounding like ...erhm fizz!) as heard on the guitar 1/4" jack socket output ...cause unknown (though Pete mentioned that he thinks it's the sound of EMI being mixed in with the pure note? I don't think it's this) String flux (maybe I have the term wrong here) = The idea that the metal guitar strings themselves are acting as a 'conduit' for the driver's magnetic field back into the bridge pickup. I have an open mind on this one - at one stage last night I was thinking about knocking up a unique string 'metal metal string...fishing gut...metal string' (the fishing gut being inserted between the neck pickup & middle pickup to break the possibility of magnetism travelling along the wire to the bridge pickup!) I think it's important we all talk the same language & make sure we can account for every one of the above (else how can we elimante them) RE the Fizz... well, using an LM386, I noticed that when I had fizz, if I took the VCC down from 9-12V to about 5.5V it disappeared....below 5V, the fizz changed timbre. I reckon the fizz may be down to high frequency distortion as produced by that nasty LM386. Comments?

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 Thanks...I only chose 330Hz, just as an initial test frequency, because it's conveniently the frequency of an open top E string (& I started that trial run at about 10.30pm last night & didn't have a whole lot of time). I will be going further up the frets tonight capo in hand (but need to muller a donor guitar pickup for its thinner wire & make a smaller coil first). I'll be carrying out test at all the guitar's extremeties (while supervising the kids bathime tonight, I'll be knocking up a guitar note/fret to frequency mapping table!) Impedance issues aside, I'm also thinking here the difficulty in driving the top strings is more likely to be the fact they're a lot more physically 'taught', but perhaps just as significantly, as we approach the higher regions of the fretboard, we aren't applying the 'drive' near the middle of the string....it's going to be a lot harder to stimulate a fundamental note just for that reason alone (I sound like Duncan Ballantyne! "& for that reason alone...I'm out") ...in a perfect world, the driver should relocate itself to be in the exact half way point of the note being played - some type of track & pulley system on the guitar face for the driver eh? (just kiddin'!)

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.