Hank McSpank

I have no big reason to plug the guitar into an amp at this prelimary stage ..as mentioned, this little workshop is in my loft & I don't have any amp facilities up there! (I will be knocking together a small breadboard amp circuit to do this soon)...I do have a guitar effects footboard that I could plug it into that has a headphone out (which I'll do tonight - * I might redo the video as the acoustic sound is masked somewhat by the ambient noise) At this stage I'm not using the guitar signal 'in the loop' so to speak...I can quite clearly hear acoustically that the sustained sound is clean...therefore the string isn't being overdriven (just like a guitar string sounds a short while after being plucked & as decaying). That strat will have a pickup disembowelled tonight & I'll nick the copper off it (it'll almost certainly be using 42 AWG, which is about 0.063mm...this should be perfect). I'll propbably also use the strat pickup bobbin as a donor 'six string driver' holder too! I've now got my Google hat on searching for a suitable lower gain output stage.

Well, a sine wave is the most efficient signal to throw at the sustainer ...& I've gone this route to get some handle on the power needed per string at the fretboard extremeties (& yes, under ideal circumstances). I think you're overcomplicating ....this is simply an early stage of noting down data. Phase lock didn't come into the experiment (after all, it was a free running sig gen)...& my initial experiment shows that when the power amp has too much gain, coupled with this particular coi (too many windings)....the string will 'excite' without any fuss. while gleaning this data, I don't have to worry myself about preamps, AGC, source pickups, etc. There is a preferential driving signal (I'm surprised you wouldn't know this?) a sine wave is it. Whilst I agree that a guitar signal differs from a sine wave somewhat, it would be quite wrong to dismiss 'sine wave input' data/results so early (this project needs more technical data... there's a fair degree of assumption, supposition, technobabble, myth & legend etc!). There are just too many variables initially that merely cloud the technical picture. For more 'real' world - well, once I've got sine wave results, I'll sample an open E string from the guitar into a wav file (& other strings), loop it & use that as the input signal to the amp , to see how it differs from the sine wave - I suspect not *that* much (& I just know that you're going to say "that's not real world, phase issues etc"...but we're just going to have to tolerate each other during my avenues of exploration in these early days!). Don't take this the wrong way, but it really is just stabbing in the dark without adopting - at least in part - a lab like approach (eg use a controlled input, monitor the output ....both audibly, visually *and* with test equipment.... observe/digest results...modify accordingly etc). Once I have something as a 'base', I'll obviously move over to the guitar as a real world signal (I can then just focus on the AGC aspect of the preamp) I just checked, but the photos have gone....I'm figuring that 5 years is more than can be expeted of any website to hold on to the photo! (I can clearly state now...in the year 2014, I will not be referring anyone back to my youtube video below!) My 'first run' single string driver is about 8mm wide & 10mm deep. I'll wind a smaller one once I get some thinner wire. (& yes, I know thinner wire = more resistance! See the video below) Here's a unedited short video clip, showing the initial basic setup and the driver (taken on a simple little point & shoot still camera, therefore not exactly high fideility...also it was raining hard & I was in the loft - so I call this one "guitar sustain sounds accompanied by rain on slate")... http://www.youtube.com/watch?v=ICa8zgd5Vp8 The point to underline, is that even though the signal across the coil is ugly the string does sustain cleanly (though I can get the string to oversustain by simply upping the sig gen signal). Also worth noting that even though I'm using a DC blocking capacitor at the input, it looks like there some sort of inbalance to do with the LM386, as initially there's only half the sine wave, until I crank the input signal up[ a lot. Since we're talking about 800mv of (ugly) sine wave across this 8 ohm coil...(therefore we could use a 1.5V AA battery for a sustain circuit!)... back of the fag packet calculations suggest (ie for this particular coil @at 330hz)... 800mV peak signal 565mv RMS current = 70mA power needed to sustain string one string 'just at the edge' = 112mW That said...it's been a while since I had to use such calculations & I'm sure someone might be able to pick holes in them! Having slept on this overnight - I'm now reasonably convinced that the LM386 chip is not the best chip to use here. Sure, it's cheaps as chips (no pun intended) & it'll get you your sustain (& plenty of it)...but if you want more control/granularity of the sustain across the guitar's frequency band (including harmonics), then it's gonna need a different output stage ...a voltage gain of 20x is just too much. For example, Put in a small 50mV signal & you've instantly got 1V across the driver, which in my opinion is too much drive for the string. Far better to use the preamp to 'control' the guitar signal, matching it with a lower gain output stage to ensure that the peak signal needed (whatever it is for your own driver) is capped & arrived at smoothly Edit: Just found a supplier of 0.063mm diameter wire (ordered some)...this should allow me to get the turn count down to meet 8 ohms.

Ok, people....we have sustain! My first trial run tonight..... Conditions... An 8 ohm ohm single string driver coil potted with paraffin wax (about 400 turns of 0.15mm around about 1cm of 4mm mild steel 'core', a reasonably powerful ferrite magnet attached on one end, ). The input signal - my PC, running a Function Generator program(test tone generator - http://www.tucows.com/preview/240287) - Sine wave preset at 330hz (open top E string's frequency). This signal is feeding into a bog standard LM386 circuit... Results...... Well, in my humble opinion, the LM386 sucks. Firstly, it has a native gain of 20 (ie no resistor between pin 1 & 8) which I reckon may be too much for this particular coil. Observations... When I feed the LM386 with a stupidly low input signal (less than 50mV as shown on the scope - at this low level, it's even hard to see the input on the scope in amongst all the extraneous junk/noise), it still easily drove the string to excitation without needing me to pluck it first. Interestingly, the power amp worked best at about 5.5V rail. At this level there was no fizz' heard on the guira's output...below 5V fizz came in, about 9V a different type of distortion was heard (similar to the so called fizz...but slightly different in its characterstic) IMHO, if I can't get a sweet spot using a signal generator as an input (ie controlled conditions - no feedback loop to worry about), then I reckon there's not a cat in hells chance I'll be able to use the string as an input signal & have any degree of control ...ie to find that 'sweet spot' (the sweet spot being where no sustain is present until the guitar is plucked then the string sustains nicely). It seems to be a binary outcome...either no sustain, or self sustain. Next steps... I now need to find a driver output stage with less gain (initial thoughts are along the lines of a simple preamp feeding an amp supplying a 'constant current'...as per what Col touched on of late) I need to make a single sting driver coil with less windings (therefore even thinner wire than .15mm I'm using to meet 8 ohms) Use weaker magnets! Less magnetic material (steel) in the driver core! Oh yeah...as I said in one of my earlier posts...I knew I'd know very early on in my testing whether a cheeky 'card up my sleeve' would work or not - well it didn't. What was the card? Using Lorentz's force to displace a magnetic field with the signal feeding into the driver (the idea being to waft a magnetic field back & forth in the same way a plectrum applies force to a string). Have a look here, you'll see that they put the magnets on the side of the coil, *not* underneath... http://ccrma.stanford.edu/~sbacker/empp/what.html there may still be some mileage in this approach, but I now think it only works well in that scenario because they're chucking a *lot* of power at their coil (& don't need to bother themselves with EMI worries) I took some video footage of the guitar sustaining (& the what was seen on the oscilloscope). I haven't got time to upload tonight (it's late here in the UK)...hopefully tomorrow.

I see you're in the UK ...Farnell have 35swg listed as 0.2mm... http://uk.farnell.com/pro-power/ecw0-2/wir...5swg/dp/1230974 As it goes, 35SWG is quite difficult to source, 36swg is 0.19mm (& as near as dammit) & marginally easier to find, http://www.rapidonline.com/Cables-Connecto.../62484/kw/36swg http://www.maplin.co.uk/module.aspx?moduleno=44 (though I'm actually using their 0.15mm variant, I can vouch for the maplin wire ...the enamel comes off with a soldering iron's heat relatively easily)

I know this isn't a PIC thread (but they offer a lot to the hobbyist!)... but I can confrim the programmers aren't expensive at all. Here's is a full get you started PIC kit - complete with PIC, Programmer & software ...http://www.rapidonline.com/productinfo.aspx?tier1=Electronic+Components&tier2=Integrated+Circuits&tier3=Pic+Microcontrollers&tier4=PICkit+2+Starter+Kit&moduleno=77048 ...or you could just buy a Clone (uses the same software/firmware as the original http://cgi.ebay.co.uk/Clone-Microchip-Deve...p3286.m63.l1177 ...to be truthful, knowing what I do now, I'd probably just buy a clone, grab a PIC chip off Ebay & a little bit of breadboard (you only need six connections from the header on the programmer to the PIC chip. Any, I digress...but once you have a dabble, there's a world of possibilities open up to projects such as sustainers. Plenty of free PICBasic Lite type programming apps about to.

As it goes, I'm at the early stages of buying SMD related kit (or more to the point...making it where possible - eg a reflow oven out of a toaster oven - http://www.sparkfun.com/commerce/tutorial_...als_id=60!) Veroboard & breadboard is so last millennium! I completely agree about AGC being needed ...my initial tack wil be with a stereo AGC bestowed preamp (obviously 3 of those needed for Hex).For simplicity (there's that word again!) & to get me up and running fast, I'll likely use an LM386 as the power amp - I'll then get a string moving 'just the right amount' at each fret position & use a scope to get some handle signal characteristics across the driver coil - ultimately hoping to glean a power figure (for each string in turn)...I can then revisit the circuit design to tweak accordingly. You latest path is in synch with some thoughts I'd had myself - it strikes me that we should all be forcusing on current through the driver, not voltage across it. But it's a niche area & I'd be the first to throw my hand up & say "Dunno much about that guv"....but thankfully nowadays...there's a world wide reference library at my fingertips! (I completely agree about that recent comment - just how did anything get invented before the internet?!) The pursuit of hex opens up all sorts of *very* exciting possibilities. I'm not sure how much time I can actually dedicate to this (certainly not 5 years!), but I've all sorts of things in mind...which would *only* be possible with a hex driver. And with Hex, I'm very consicuous that 'fade' when bending a note will be a problem, so I'm envisaging a selectable 'solo' mode, where the note being played is fed to it's own string driver & the next lowest string - then when I player bends up & it moves away from the driver...it'll move into the zone of the next driver - since it'll be only solos, this oughtn't to be a problem. Also as I quickly mentioned... totally controlable harmonics 'on demand'. If nothing else great fun trying! PICs aren't in the least bit expensive - they're only about 2 quid apiece - for example, here's perhaps one of the most used variants http://uk.farnell.com/microchip/pic16f627a...equestid=404273 (but being a cheapskate, the PIC I'm using is a PIC16f690...it comes bundled with the Manafacturer's learning package ... http://www.rapidonline.com/Electronic-Comp...048/kw/pickit+2 ..I can heartily recommend it, though I now know that the PIC they bundle with that kit is not exactly a 'starter chip' - too many whacky 'gotchas' that a learner shouldn't have to get bogged down with so early on). It's taken me a fortnight to wrap my head a round the whole end to end process (which language to use, how to code it, what apps to use, how to program the PIC, header cards etc). I'm still at a fairly elementary stage - barely enough to get my coil winder going - but it has wet my appetite...I can see massive potential here (not necessarily for Sustainers).

Just a couple of minor points (my loft beckons!). I wasn't suggesting for one moment you'd approached your sustainers will nilly (ie with my "Nike T Shirt - just do it" quip)....the comment came from your line... " I'm still not entirely sure why you don't just make a test coil of a known design and see how that goes, if only for a reference" that's my point...I'd rather think it through ad infinitum (beside my loft is too cold to "just do it"). Such is the written format - open to misinterpretation. (I also regret the boat analogy as it's allowed you to go overly wordy! lol) Re , your tele switching photo (which shows an awful a lot of interconnections). Well, without sitting down with a wiiring diagram & going through it wire by wire (& I've no intention of doing that even if you scanned one!), the more interconnections/wires, the higher the possibility for grounding problems....which might well have resulted in a failed simple micro switch scenario. Re the simplicity & my pursuit of hex...don't muddle the two towards scoring points! I've no wish to get complicated where simplicity will do...but from the outset, I've said there are major synergies with Variax & midi guitars...both of which I'm into in a big way (I also have a sexy little concept I wish to try which will yield any harmonic on demand ...3rd, 5th, 7th, 12th but this definitely necessitates a hex driver...all will be revealed once I've tried & failed!) - therefore my pursuit of hex, overides/negates the pursuit of a simple mono driver - I will however pursue simplicity whenever possible but only if it dovetails with my own particular requirements. Anyway ...thermal underwear & gloves on....to the loft & beyond. (on tonight's menu - getting my coil winder to drive some 7 segment LED displays, which aren't striclty need as the PIC turns off when it reaches a user predefined figure...but I'm @n@l that way...& you can never have enough LEDS - 7 seg or otherwise - on any project!)

Here's a quick attempt at a possible explanation of what Pete is talking about. First, go here and read about why star grounds are used in valve amps. Now consider Petes 'piggy-back' driver design. A driver coil with relatively few turns in very close proximity to a pickup coil with thousands of turns. The two coils act as a transformer, the current in the driver coil inducing a current in the pickup coil (the pickup coil will develop a relatively high voltage). With the pickup coil connected only at the ground, any current induced will flow through the ground connection. Surely it's possible that, depending on the driver circuit, ground layout, quality of components and construction etc. this could add noise and potentially cause parasitic feedback? Think about the river analogy on that web page... cheers Col Those are my bolds - it seems we're trying to conceptualize why a simple switching solution won't work! (& I thought we're all chasing simplicity?) I think Pete needs to clarify (or anybody come to that) ...has the switching idea that discussing, actually been tried out under test conditions? Because Pete pretty much disregarded this simple concept idea a couple of posts ago. (and zfrittz6 said it worked) The reason I'm labouring the point, is because it's an important issue. When choosing a sustaining device, a electric guitarist (or come to that a designer), has few options... 1. Remove the neck pickup (not good - you lose the pickup that was meant to be on the guitar!) 2. Buy a sustainer combined/integrated with the manafacturer's pickup (again not that great an option as your getting a pickup 'bundled' ...ie it's not your first choice) 3. Keep the Guitar's original pickups, then integrate a small sustainer driver & get 'creative' with the placement and/or switching! 'Creative' here being - simply disabling the sustainer when any pickup other than the bridge pickup is selected. Beautiful in its simplicity? Of course the compromise here is that you can only sustain notes sourced from the bridge pickup...but in my opinion, for most guitarists, this would likely be the lesser of all evils. We can all come up with plausible "what ifs", "mights" & "perhaps" theories (but presently, I'm not swaying - ground potential is ground potential :-) - & unless someone has tried this out under decent test conditions (proper earthing layout within the guitar, decent guitar cable etc), it would seem quite wrong to dismiss one of the few options open wrt keeping the original pickups on a sustainer bestowed guitar.

No...the ground should stay clean...no matter what. As much as you;'re struggling to explain, I'm struggling to see how any EMI can interfere with the guitar's ground path. A good ground should never deflect from what it is ....a reference point which isn't deviated from. That reads like you're overcomplicating/fogging the issue Did you try out zfrittz6 idea to see how it performed? Like I say, I can't think of any reason why it wouldn't work. I mentioned earlier, that anyone adding a sustainer to their guitar should be able to keep their chosen original pickups. His idea is certainly elegant in its simplicity...& I'll be investigating this path (that'll be the final stages though!). before I even lift a soldering iron, I want to ponder the issues time & time again...of course, there's a danger you can get yourself into a recurring loop, but it's much quicker to think through (again & again) designs, to foresee & address the problems in 'grey matter', than to have to react to them after just putting your Nike T Shirt on and "Just Do it" (because 'making stuff' is *real* time sump) I can't speak for David, but there's little point in me making a test coil of 'known design' & then trying to use it for a totally different setup (& I'm not sure there is a 'known design' for a one string driver?). That's a bit like saying "why not build a rowing boat - plenty of known designs out there"...but what if the designs out there aren't suitable for my journey? This thread has obviously evolved into the 'mother thread' for those who want a cheap (?!!), fun project towards building a mono sustainer (& as you've suggested, why reinvent the wheel if that's all a visiting dabbler seeks) - but surely the mother thread still has the capacity to dock mono sustainer 'offshoots'....or do you want to keep the thread 'pure' to those following your thin driver? PS As an aside, I recently bought an awful 'catalogue Strat copy' off Ebay (for me to hack the hell out of)...I was quite shocked at how much even awful Strat copy variants are getting bid up to on Ebay - so much for there being a credit crunch when a chipped, awful strat copy sells for £25+ postage!

But you've not given a technical reason how ground can be anything else but ground? With your antenna analogy...it's the 'hot wire' that picks up any radiated signal ...not the ground (the ground is merely a reference). Like I say, if you have good grounding internally throughout the guitar & a good quality cable to the guitar...there's no way that ground can be anything but ground, so lifting the hot from the deselected pickups ought to be sufficient. (is it possible that when you tried some EMI was still being picked up by the active pickup & this was assumed that the deselected pickups were interfering with the setup?) Of course, I've certainly considered that they might not work...but I don't consider the time/effort I've put into my coil winder as wasted. I now know how to write programs for PICs (& I've a whole load of other niggles needing a solution around the house that could easily be solved use a PIC!) In between all of this, I'm about a 3rd of a way into a DIY CNC machine build (no hacksaws & CD cases this end!) - this bit of kit will be essential for making a decent bobbin (my 'mother' bobbin needs to hold six bobbin-ettes). I've always hankered after a CNC machine (every shed should have one!) so this has made me get off my backside & build one. The 'X' plane is finished...two more planes to go! (to get an idea, what a boon this will be from about 4m33secs in ...imagine that thing cutting out a bobbin from acrylic!) Yes, the negativity does permetate through a bit! We're all coming at this with different skillsets & knowledgebases. I realise this is going to be a tough nut to crack. This is another reason why I've gone the way of an automatic pickup winder (& diy CNC) ie once finished, it'll piece of p1ss to knock up a new hex driver design. Since I'll be able to crank out drivers quickly/bobbins quickly, it's then just the law of averages wrt getting the right driver design!

I'm a little puzzled over that statement ...perhaps you've tested the idea & had problems? In my experience ground is ground.... sure, the unused pickups will stilll have their ground connection 'starred' back to q common ground, but I'm puzzled as to why tsuch a mini switch would be a problem in practise? (ie if you have very good quality guitar cable & excellent star wiring in your guitar, the driver EMF shouldn't be discernible via the unused pickups' ground path. Well, I've been in radio silence wrt driver construction here, as I had to go off on a tangent to spec/design/build a hex coil 'automatic feed traversal' system. For this, I had to learn about basic PIC Programing (and for me, that was painful!) & then knock up a circuit to support the PIC (ie PIC -> stepper motor electronics etc). Anyway, my PIC program duly finished I tested it out roughly last night on a breadboard lash up - it seems to works! (ie I can now instruct the PIC .."after 60 turns of the main motor, then reverse the direction of the wire feed traversal helix motor" the idea being to have some form of flexibility & replicatability ...which is obviously important when you need six of them! I now just have to neaten the whole rats nest up & give my coil winder its first dry run (probably Sunday night now). At last, I'll then be ready to start experimenting with hex driver circuits (and hey, here in the UK the clocks go forward this weekend ...meaning it must be nearly warm enough to spend more than 30 minutes in my freezing loft!)

Interesting. I've been toying with the idea of winding a coil around the whole driver perimeter (hard to describe without a diagram - ie where a normal pickup mount would be wrt its pickup!). Then, when the sustainer is active....apply a small voltage to this coil - you've then got a non-alternating electro-magnetic field (this coil won't generate an EMI itself ....except when first energised - I need to think about that one!), this electro-magnetic field ought to stop some EMI spilling outside of the driver's immediate vicinity & into the other pickups. Needs some experimentation! I'm working on the basis that I don't think any sustainer solution should force the guitarist to sacrifice a pickup (as with the commercial offerings)...& surely the simplest way around this is to locate the driver as far away from say the bridge pickup as possible & only allow the sustainer to work when the bridge pickup is selected (ie disable the sustainer in any other pickup position). This can be achieved by use of a micro switch on the pickup select lever ie underneath the scratchplate mounted on the pickup selector switch (which has been previously suggested by a Spanish chap on here - Juan) ...or a simpler offering with a bespoke switch mounted to the face of the guitar which would be made/broken by the 5 position pickup selector

Two 9V batteries in series... -ve term 9V +ve term ....<-Common (Ground) point ->.... -ve term 9V +ve term. Mid point is 0V.....or did I misread your question? The problem with using two batteries to supply your opamps using the above method, is that they may have slightly differing potentials, therefore without extra regulation circuitry, they'd possibly not bias the opamps symetrically. Using a resistor divider network off a single supply battery, will ensure the mid point voltage is always mid point.

Nowhere at present! (this is just one of many projects I have on the go!) I did manually make a 'one string driver' & then quickly realised I need an easier, more precise, repeatable way of winding the six needed! So I'm now knocking up a 'automatic wire feeder' (for my pickup winder seen in a photo I posted up a page or two back)....it's loosely based on taking a winding motor 'tach pulse' to trigger a monostable -> into a PIC (programmed as counter), driving a stepper motor turning a threaded rod. The wire will feed onto the driver bobbin over the threaded rod - here's a youtube video of something similar- Sure, it's certainly overkill (& has taken me off on a short vector), but I'd like to learn about PIC programming anyway .....& you can't beat having an end goal to help get you learning!

I'm still waiting on some parts arriving (I see a lot of trial/error ahead, towards establishing a suitable hex circuit!). One of the chips I've ordered to expeirment with is a TDA7284 - a stereo preamp with AGC - I believe a Spanish chap did pass through here who had some degree of success using that particular IC?

Aye it is indeed ..but one of my lines of thought goes - rather than chasing the elusive 'perfect AGC' circuit - which certainly for a mono driver the circuit would have to try to be all things to all strings (a bit of a tall order bearing in mind the variety of string tensions, string diameter, string material, frequencies etc), why not just use a footpedal to supply a Control Voltage to the VCA? Why? Well in much the same way a guitarist *wants* to be in control of his other effects, why not have an expression type pedal that controls the amount of sustain applied on the fly! A foot pedal would make for much easier dynamic control of the amount of sustain required by the player. For example... Wimpy .009s on the upper frets which makes the sustainer's effect a bit weak? ...no problem sir, just push that expression pedal down a a bit further. An overpowering sustained open G string? ....back off on the expression pedal. This concept beds in well with my pursuit (goal) of hex sustain ...ie one CV voltage across all the six amps.

What a small world! One of my other (multitude) of ongoing parallel universe project-ettes, sees me working on a faulty Digitech footboard (RP14D) .....& the intermittently faulty Wah circuit on this Digitech footboard has a suspect THAT2159 VCA! As you say, there's no info on the net, so I emailed' THAT' and received their THAT2159 datasheet within the hour! I've uploaded the datasheet here for anyone that wants it... http://freepdfhosting.com/6239f0ff86.pdf Here's an extract from their email... "We have the Design Note 137 which explains how to upgrade circuits using THAT 215X series VCAs, http://www.thatcorp.com/datashts/dn137.pdf Direct replacement for the now obsolete THAT2159 (fairly cheap too).... http://uk.farnell.com/jsp/search/productde...jsp?sku=1354168 Since then, I've been pondering how this very VCA might fit in to a sustainer context! Re Class D amps......hmm, here's an interesting ic - a 3W mono class D amp with Automatic level control (preset by just one external resistor!)... http://www.analog.com/static/imported-file...ets/SSM2317.pdf The catch? It's absolutely tiny! And therefore needs to be used with this evaluation board (which is quite costly at about £42+VAT )... http://media.digikey.com/photos/Analog%20D...M2317-EVALZ.JPG http://search.digikey.com/scripts/DkSearch...SM2317-EVALZ-ND

Humour me here ....who/what are ROG?!!

Humour me here ....who/what are ROG?!!

My first creation - no, not a sustainer, but an individual hex string driver winder. Bits needed include an old DC cooling fan, a 10mm drill keyless chuck, a little Pulse Width Modulation Circuit to control the motor speed (a cct based around a 555 timer - http://freecircuitdiagram.com/2009/02/01/p...ontrol-circuit/ ), a reed relay (as a rev counter) & this guy's pickup winder program... http://pickups.myonlinesite.com/programs.php , a rod to support & allow tensioning of the wire - Oh yeah, and lots of hot glue.... (sure, it looks ugly ...but it's very functional!) The above 'proof of concept' PWM motor speed controller mash up, has now been migrated to a somewhat more permanent stripboard! Also the pot you see will be going in a volume footpedal, to allow me to control the motor speed with my foot. Total cost - just £3.00 (for the keyless chuck) most of the other stuff, I had lying around (John Noakes would be very proud) I've nicked a mini thread bobbin from my missus's sewing machine kit (she'll not be happy, but needs must!) along with a small bit of 5mm diameter mild steel rod....ready to roll soon! What does everyone else use to wind their drivers?

Wow...I'm impressed you've honed your circuit without access to at the very least a scope! (genuinely!!) They're actually not that expensive nowadays - I paid about £110 for a dual trace Digital USB storage scope ...this is an external box solution which is hosted by my PC ( http://www.darkwire.com.au/html/dso-2150_usb.html ). You could always buy a secondhand one for the project (they're about £50 on Ebay for a Tektronix 40Mhz model) & then flog it on afterwards - that way there'd be zilch in the way of financial loss. I'm fortunate to have picked up a HP Sig Gen that my work were literally throwing out...but again, you can get software to run on a PC that serves as a sig gen (using your soundcard). I can't even begin to imagine how anyone could dedicate the amount of time needed to get results without test tools. Sure, you can get quickly the generic results by following the blueprint by many on here, but it'd be rather difficult to take this project down any new avenues easily, without at least seeing what the signal levels are across the driver (along with seeing if the signal is distorting etc) - without a scope you're literally are stabbing in the dark (or at least stabbing in a very low light room!). How else are you going to see the frequency response of your amp/driver - see what phase changes there are between input & output...& so on? Is anyone on here using one?

Just out of curiosity...how many on this thread have access to test kit? (an oscilloscope & signal generator, etc) There seems to be a lot of discussion about circuit design, phase, bandwidth .....but little mention of measuring it. I still think to get in the 'initial' ballpark circuit area (amplification wise), it'd needs an approach something the following... 1. Knock up a basic power amp (LM386 etc or whatever) ....connect it to your driver mounted on the guitar (or 'guitar plank' test rig!) 2. Inject 82.4hz (Open E string) from a sig genny into basic LM386 power amp. 3. Crank up the power amp input via the Sig Gen until the open E string starts vibrating sufficiently - measure the input to the power amp. (& the power amp output across the driver - just for reference, power levels etc) 4. Repeat steps 2 & 3 for the other string...right up to th 24th fret for the high E string & then finally doubling to ensure you capture the required harmonic content) 5. Construct a circuit to provide the right input level for your LM386. 6. Refine circuit accordingly!!! Sure it's step 6 where all the magic happens, but to get you to a good basic stage for your own particular driver, I can't think of any quicker way?

And what about potting with paraffin wax? (apart from chance of air pockets)

For anyone reading in the UK....Maplin has a good variety of sizes of enamelled wire, which was surprisingly hard to find on their site (ignore the photo...that's their large diameter stuff!)... http://www.maplin.co.uk/module.aspx?moduleno=44 (you'll see that they have 0.19mm diameter - product code YN90X - which will suit those going for Pete's well R&D'ed design) (it's not necessarily the cheapest source, but nevertheless they have some of the thinner stuff that I couldn't even locate on Ebay, Rapid etc). Handy if you'd be placing an order over £35 as it's free delivery then (don't forget Quidco too!). For magnets, I ordered some small ceramics from Ebay (on the basis they're still quite strong but can be chopped up to suit). There are plenty of ceramic magnets to be had on Ebay, for example.... http://www.tinyurl.com/d6lwvd (if you have kids, they can have some real fun with half of them! Not recommended for reall small kids under 5 though) One thing I've not been able to source, is pure iron rod (I'm pursuing the dark side - hex drivers, so I'm not looking for a long thin driver core like most)...so it'll have to be mild steel for the time being.

Most of those - whilst obviously being variables - are arguably sufficiently within certain real life 'givens', so shouldn't impact the power figure *that* much ...but I guess I'm coming at it on a per string basis (ie hex vs the mono solution pursued by the majority on here). It'd have been great to see info along the lines of... 'Individual string' coil - 400 hundred turns of 0.15mm wire totalling 24 ohms, driver handheld approx 5-7mm above an open E string (10 gauge) immediately adjacent to the neck....this scenario needs an output signal of 8V peak to peak (measured across the driver) to excite the string sufficiently. Once we have such data on a per string basis (open string thru top fret), then we have something to shoot for ...and can design a circuit to suit (whether mono or hex). What I'm reading often throughout the thread is "tried driver design MK27...the open G string was fine, but couldn't get E to sustain" Without wanting to belittle the research that's gone on hitherto, I'd say to get even results, the driver circuit is *very* important ...certainly as important as the driver itself IMHO. I'd say certainly, just so long as the power figures are quoted with all the associated pertinent info....else it means anyone wanting a stab at taking this further, either has to fall into line & adopt the same mono driver as everyone else (with perhaps some of their own tweaking of the circuit to suit) - & where's the progress in that? Or else start from scratch! That said, I guess not everyone has access to a scope or Sig Gen (fwiw, I'll be using a sig gen set the same at each string's frequency extremeties to see what input/output the LM386 power amp needs for the driver to get each string rocking) Thanks for the info (but I do relent that info for a mono driver perhaps has too many variables, ie wider frequency range, wider variation of string thicknesses & construction, material etc) - & thanks for the link. Anyway, my parts are arriving bit by bit...I reckon I have all the components to crack on ... the breadboard, the wire (not 0.2mm - but finer at .15mm), the coil core (in various diameter mild steel bars), some magnets...I've even got a custom cheapskate pickup winder in the offing (parts needed being a 48VDC fan, a 10mm keyless chuck, an old wah wah pedal & a variable bench power supply!)...just need the weather now!