curtisa

Jaycar or Dick Smith will do. I was only talking about getting another cheap one to test with, not to permanently install. Locally? Try Pro Audio in Canberra or Venue Music in Sydney. Pro Audio's online catalog isn't much, but their physical inventory is massive. They've got a freecall number, so drop them a line. I believe Venue Music have a 10 day, no questions asked, money-back guarantee on any sale. So if you go that way, at least you can return it.

The top trace looks very much like parasitic oscillation during negaitve excursions of the driver signal. Have you got any supply bypassing of the 386? Say 0.1uF + 10uF in parallel? That might help tame the parastics a little without resorting to a zobel network. This kind of stuff is pretty good actually, and is something I failed to do when I was first working on the sustainer - I never got the chance to scope the output of the sustainer circuit. I wonder how much of the fuzzy bleed of the sustainer I (and others) am currently getting with my basic setup is simply down to a horribly distorted LM386 output?

Ack! 10 bucks for a pot?!! I digress... As an example this pdf is from Alps' online catalog for one of their pot styles. If you scroll down to page 6 it shows the various types of taper you can order from their catalog. How much different? The difference at 50% rotation will change depending type of pot you have. On the graphs in that pdf, "B" taper is 50% resistance from either lug to middle at 50% rotation (as you would expect for a linear pot). "A" taper is about 25% from middle-right lugs, and 75% from middle-left lugs. "C" taper is similar at 50% rotation but the the way it changes in the first half-turn is completely different. Can you sub in a cheap Radio Shack 500K log pot and see if it works? That way at least you can eliminate the pot as the culprit.

Hehe. I bought a bunch when I built a pair of clones of an SSL mixbus compressor, only needed 6 and THAT supplied 12. And yes, they're the SIL versions, so they're easy to work with. Yeah, pretty nice chips really. Predictable response curves, low noise. Provided you can generate a DC control voltage (doesn't have to be true-RMS or anything fancy) you can do whatever you want with them. Only drawback I recall was that it needs a minimum of +/- 5V supply, which puts it out of reach of a single 9V battery application. HOWEVER, there are ways to generate negative rails to run the buggers from a single 9V source via a charge-pump DC/DC converter based on a 555 timer. No dice with datasheets here either. Big heatsinks sounds like power amp IC's. Be very unusual to find anything like low-level fancy audio jiggery-pokery going on in a chip designed to dissipate lotsa watts. Early VCA's were extremely temperature intolerant, so it'd be unlikely that there'd be any such goings on in a chip like this, not with any real degree of quality at any rate. You can buy direct from THAT, but minimum quantities do apply (eg, 25 for the THAT2181). Mouser in the States has all the THAT products in most formats with no minimum order. I have used Mouser to get some hard-to-find stuff that I can't get here in Oz. Small Bear Electronics (also in USA) carries the THAT218x and THAT4301 VCA chips for reasonable cost and no minimum order. In the interests of sustaining the sustainer development (hyuk!), would you like me to send you one of my 2181's? PM or email me if you're interested.

Not really familiar with Stewmac's parts system. Do they use a long shaft to identify the pot as being log taper? Could they have accidentally supplied you with the wrong taper? The pot should be stamped (or printed) with its value in ohms (or K ohms) plus a single letter code describing it's taper, eg "250KA". The last letter is the taper type - "A" is log, "B" is linear, "C" is antilog. The linear and antilog types could give the behaviour you describe, particularly antilog. Digi2t has good info there too. Yep Near enough is close enough Not easily, unless your multimeter has a capacitance function. Although if the cap has got just "47" written on the side it's more than likely just 47pF as you say, which is far too small to be of any use to you. You definitely want something that says "0.047" or "0.047u" or "47n" or "473" - they're all the same value, just shown in different numbering formats.

'Course, you could make the AGC circuitry more repeatable and universal by utilising the more specialised VCA chips, thus doing away with the multiplicity of trimmers required just to get the system working. Mind you the trade off in that case is cost - would you rather spend time and money tweaking the circuit once it's built, or spend more money at the outset and buy a dedicated $10 chip to do it all for you? I should really re-explore the AGC system on my setup. I have a bunch of spare THAT2181 VCA's kicking around at home doing nothing...

The sudden step change in level on the volume pot sounds like you've installed a linear taper pot in place of what should be a logarithmic taper (or audio taper) pot. The tone pot not working at all sounds more like an open circuit, not a short. The continuity you're measuring from the RH lug on the tone pot to ground sounds sorta OK, but I'd say you're measuring in parallel with everything else in the circuit, hence the changing readings as you move the controls around. I'd say the key continuity points to check on the tone circuit would be the input side of the tone pot (ie LH lug on the volume pot to the middle lug on the tone), RH lug to cap, other side of cap to ground - all should read zero ohms. Also would be worth verifying if the tone pot is any good. You'll have to disconnect it from the circuit to check it though. Once you've got it out measure with your ohm meter the outer two lugs to make sure the pot's value is what it says it is, and also between the middle lug and either outer lug while twisting the shaft to make sure you can see its resistance change. The cap size is important too - it's not mentioned in your diagram what value it is. If you've installed something too small of value it won't work. Or at least technically it'll be working, but the frequencies it affects will be so far up the audio band its effects will be inaudible

Fundamentally? Not much difference at all. They're all the same value. However there may or may not be certain tonal differences between the three that some purveyors of the finest snake oil will have us believe For a buck-fifty for each style, why not just get all three and swap them out as you see fit? IMHO I doubt you'll hear any difference between the three, but it can't hurt to try. FWIW I believe the first and third options you have there are exactly the same, except that the third has a higher voltage rating.

Shouldn't need to be a company to buy from RS, I've done it myself heaps of times. Farnell is similar, but like RS their prices are fairly steep. There'd have to be plenty of other options for you locally though? Radioshack? Fans should be easy to get at almost any electronic components retailer. Other online places you could try that shouldn't cost the earth would be Mouser and Digi-key, both of which allow individuals to buy online.

One other thing to consider is cutting the slots for the slider post to fit through (VERY difficult to do neatly, especially if you're putting them in to wood). My personal preference is probably just the good old rotary knob - sliders are more expensive and more fragile, plus because the post fits through an open slot they attract more dust and crap into the innards than a regular rotary pot does, making them less long-lasting in harsh environments. You'd probably end up bumping the controls a lot while playing too.

Are you working under flourescent lights? Nearby TV or computer monitor? Light dimmers in the room? Near your soldering iron? Maybe one of the coils in the humbucker is being shorted out (loose wire, shorted pickup winding?) and it's effectively running as a single coil pickup?

To sum all the six outputs while leaving them available for MIDI processing requires use of an opamp summing circuit, basically a simple mixer - each of the 6 outputs get summed into one signal which prevents cross-loading back into the MIDI circuitry. Here you go, can't get much simpler than this. Just add a power supply: http://devices.sapp.org/circuit/mixer/ Google and ye shall find.

Assuming by "core width" you mean the distance from the outer edge of the treble pole piece to the outer edge of the bass pole piece, I still measure 57mm in mine. I don't think it shrunk too much since I washed it last

PSW is correct - it's to do with impedance mismatching. A passive guitar pickup has a relatively high source impedance. The little Champ amp was a relatively low input impedance. Think of the source impedance of a device as a car and the input impedance of a connected circuit as a trailer. If the car is under-powered (ie source impedance is very high) it'll have a hard time trying to lug around a heavy trailer (input impedance is very low). If you have a more powerful car or a lighter trailer the effort required to move the trailer will be less. Loading down a guitar pickup will usually result in low output and loss of treble. What's required is a buffer between the guitar pickup and the amp - something that will provide a high impedance input for the guitar pickup and a low impedance output to drive the amp. Using the car/trailer analogy, I guess you're looking at dropping a big block Chevy V8 into a Morris Minor to pull that trailer up the hill

The AGC will help, yes. Essentially it helps "normalise" the response of the driver a little. But my system is AGC-less and I can only get the lowest notes to sustain harmonically. My suspicions are that inductance (or lack of it) and low frequency rolloff of the driver is a a significant factor here. Serious impact how? Sorry, I missed the post you made on that topic The coil forms a simple RL high-pass filter. You need sufficient inductance in the high-pass filter in order to ensure that the lowest frequency of interest is not shunted to ground. The actual maths escapes me at the moment, but I reckon it's in that RDH chapter 5.

I am not sure why they have the design they do, but I suspect they are made in some transformer winding company with standard technology. As we have discovered winding elongated coils around a thin core is problematic while their dual bi-lateral coils fit a more typical coil winding model. I would think that the reason why they use laminated cores and larger coils is for the same reasons you need to do so for making efficient transformers. Laminating the core reduces eddy current losses in the core and makes the transformer much more efficient. Also helps push up the inductance too. Winding lots of turns on increases the inductance and also directly affects the lowest frequency you can pass through the transformer. More inductance = better lower frequency response. The classic old Radiotron Designers' Handbook has an excellent chapter on transformer design: http://www.gyraf.dk/schematics/RadioDesign...ransformers.pdf This could also be a significant reason why the thin driver tends to be a little hard to get going on the lower strings in fundamental mode. With only 100 or so turns on a solid steel (or 6 pole pieces) core you don't have sufficient inductance to drive the lower notes in fundamental mode and the lower notes tend to always want to start harmonically (or not at all). Also, the thinner strings are more difficult to drive probably because of a combination of their smaller surface area and the tension of the string. Having a more efficient driver would make them more responsive. As simple and as effective as the thin driver is, I suspect that Sustainiac have the right idea, and have done so for reasons other than just because a transformer winding company can produce it for them. For example, I measured my driver's inductance as 1.97mH and a DC resistance of 13.8 ohms. Using the forumlas in the RDH handbook for calculating low frequency rolloff I get 2.2KHz, which is incredibly high. Fundamental tone in a guitar's low E string is 82Hz - I'm a long way short of being able to drive the low E string fundamentally. According to RDH I need an inductance closer to 31mH in order to have sufficient low frequency response in the driver (assuming we aim for a coil resistance around 8 ohms), and the only way I can do that is to use more turns of thicker wire, or change the core material.

Good news on your coil winding trials, Pete. Something that just struck me after reading the last couple of posts: Have you thought about offering the sustainer as a one-piece pickup cover replacement option? It may be considered a problem by the user that the driver sitting under the existing pickup cover sinks the pole pieces by 1-1.5mm. What if you pre-installed the driver into a pickup cover that just swaps out the old one? Maybe use a "blank" cover (looking like EMG's) , permanently install the driver coil under the top. Maybe even mould a custom cover with the driver built in (would help solve the problem with setting the coil) and the wires secured down the side of the cover to prevent them breaking off when installing. The cover could even incorporate a secure termination point for the driver wires. Would it be possible to "practice" with a bunch of replacement SC pickup covers - cut off the top and re-set a new top using epoxy or plastic moulds with the driver built in?

It will be veeeeeery small. But why not wrap 10 turns of enamelled copper wire around a string, measure the inductance and work out permeability by substituting the inductance and turns into the usual equations? In fact, from the veritable Wikipedia: http://en.wikipedia.org/wiki/Permeability_...tromagnetism%29 ...the permeability of nickel (guitar strings are mostly nickel?) is 125 micro mu. Steel is about 7 times greater. That should give you a band of figures to try out in your calculations

AC would be my guess. I believe polarising any transformer circuit with DC is a bit of a no-no unless it's designed to take it. Pickups may not like it if you burn a DC current through the winding for a long period of time. But I'm only really going on my experience with input and output transformers in pro audio gear, and industrial current transformers in my day job. Pickups may not matter either way. Still, AC current would be my preference, just to be certain. However, you'd need to watch how much current you're passing through the coil to make sure you're not over-heating the coil. The last thing you want to do is build a perfect driver coil, burn it in, and in doing so soften the insulation on some of the turns and cause a shorted winding, rendering the driver useless. If you were super careful (and I mean REALLY super careful - epoxy is highly flammable) you could bake the assembled coil in an oven on a low temperature, say less than 100 degrees C. I baked my driver that way, but I was using PVA as the curing agent.

OK, not "zilch" as such, but the pickup cover on the Pac112 is a pretty snug fit from side-to-side, and you'll have to run the 0.2mm winding wire down the inside of the cover to some secure point so that the wires aren't easily damaged either during manufacture, installation, and everyday usage. In my situation you couldn't make a termination board on the driver itself and then run thicker wires down the inside of the cover, it'd bulge-out the side of the cover. I guess the guarantee that has to be made here is that the coil really con be no bigger than 1mm thick under any circumstances! And for Col: Using that inductance calculation page, with my driver I calculate 1.97mH inductance at 2KHz. I also tried it at 440Hz (was that the frequency you used? I can't remember...) and got the same result. Pretty small inductance, and not surprisingly either - A core consisting of a solid steel blade will have a pretty low permeability to start with, and 100 turns of 0.2mm wire will give a pretty low inductance. My driver also has a DC resistance of 13.8ohms, which is almost double what the apparent ideal is. Just for shits 'n giggles, I measured the inductance on the single coil pickup winding that the driver is attached to - the DC resistance is 4Kohms and I calculated an inductance of over 3 Henrys. Given my original results on the driver that must be pretty close, as the pickup winding will have thousands of turns (as opposed to my 100 turns in the driver), and inductance goes up exponentially in relation to number of turns. All results measured with a Fluke true-RMS multimeter. I've been out of the loop for too long - do we want a high inductance at a given resistance or a low one?

What about using modelling cement as the curing agent? The other thing I thought about when I was at Bunnings the other day, there is some two-pack product they have there in the craft section that comes in tiny little bottles all the way up to big 2 litre tubs. It's called Glasscote or Gloss coat or something like that. It's really meant to be used to pour over flat surfaces to give a super high glossy clear finish without brush strokes. It's also super hard wearing. And mine on my Yamaha Pacifica 112 are the following: 1. 5mm 2. 57mm (outer edge of bass polepiece to outer edge of treble polepiece) 3. 15mm 4. Zilch, see number 5 5. Don't care either, but the design of the Yamaha pickups are such that the polepieces are flush to the top surface of the pickup with the cover in place, so anything under the cover will make the polepieces disappear under the surface of the cover. The cover also has a fair bit of slop in fitting over the pickup so you could easily get some small guage wires between the bobbin and the cover to make the external connections. The only drawback is that the cover is aligned properly over the pickup by the polepieces which then stop it from wobbling around when the whole assembly is put together and held by screws. So raising the pickup cover by even a small amount by putting the driver underneath will put the whole thing out of alignment and it will allow the cover to move around over the pickup. The resulting "sunken "polepieces, which don't bother me much aesthetically, may bother other users. Also the fact that the polepieces are below the level of the pickups may cause dirt and gunk to enter the pickup/driver and cause rust and damage. Looking at the construction of the Pac112 single coil pickup it looks identical to the pickup I used to make my original sustainer (pickups were from an early trashed Yamaha RGZ). On that one I hammered out the 6 slugs and cut a new slot into the bobbin to accept a taller steel blade, so I didn't have to worry about sunken pole pieces or misaligned pickup covers. I think the idea of being able to universally fit the driver under a single coil pickup cover may need to be rethought as not everyone will be able to drop in the driver under the cover without some major re-working of the pickup itself - say replacing the stock picup slugs with longer ones. Complex numbers, vector numbers etc. The "2" bit is the "real" part of the number. The "34i" bit is the "imginary". It's a way of experesing vectors in one mathematical "term". Think of the two parts as the "run" and a "rise" or a triangle - the 2 is the horizontal base of the trinagle running from left to right, the 34i is the vertical side of the triangle running from bottom to top, both lengths being at right-angles to each other. The hypotenuse of that triangle (ie the third line joining the start of the 2 on the bottom-left, to the end of the 34i on the top-right) is the value given by the expression "2+34i". When talking about impedances the "2" is the DC resistance and the "34i" is the reactive impedance. Volts and current can also be expressed in such ways, showing amplitude and phase shift. You can also re-write the expression in more useful ways by working out via trigonometry the angle and amplitude of the hypotenuse of the triangle. So by trig, 2+34i would equal 34.06 at an angle of 86.63 degrees. Errrrr...dunno if that really helps or not... I'll do the impedance measurements on my driver today and get back to you.

Hello once agin Col (been a while!), I used this site when I custom-wound some multi-tapped inductors for an EQ I built a while back: http://et.nmsu.edu/~etti/fall96/electronic...uct/induct.html You will need access to a sinewave signal generator and an AC voltmeter that can read 1KHz accurately though. However, you don't need to worry about permeability of different cores and air gaps to get an accurate reading, just measure what you see and plug in the numbers into the formula. If I get any spare time over the next few days I'll do the measurements on my driver and see what I come up with. Same here Pete - I'll make some measurements as time permits on my SC pickups and report back.

I haven't posted in this sustainer thread for quite some time, but given that Pete has been generous enough to ask me to be one of his beta testers, and the amount of criticism that has been flying around in the last couple of days, I thought it might be time to pipe up a bit. Firstly, I really must thank Pete publicly for giving me the opportunity to be one of the select few to trial out his latest sustainer ideas. If it weren't for me stumbling over the Project Guitar forums, and also bumbling in to his original Sustainer Ideas thread, I doubt very much I would have even bothered to attempt to build the DIY sustainer. I had toyed with the idea of a DIY E-bow for a little bit beforehand, but always arrived at the conclusion that it was too complicated and not really worth the effort - I probably would have just gone out and bought the commercial alternative. PSW's original experiments, and the consequent contributions by many others involved at the time, gave me the drive (no pun intended) to go out and build a sustainer from the information contained within the thread. Over the period of about a month I was able to build such a device and also provide some of my own knowledge and experiences to others in order to hopefully refine their experiments with both the driver and the circuitry. Eventually I had a sustainer-equipped instrument that I felt suited my needs well enough for me to just leave it be. I figured that one day I might be able to return to the project and refine it further if it took my fancy, but for the time being it was working for me as well as I needed it to - I was using the system with my band, both live and in the studio, and it appeared to work reliably, even if it still had a couple of quirks. I always thought that the whole intention of the DIY sustainer thread was just that - it was Do-It-Yourself. Originally Pete's experiments appeared to be quite radical and his original posts regarding the construction and implementation of his then-hexaphonic system were quite cryptic and closely-guarded. I can fully understand why he chose to keep some of that information close to his chest, especially seeing as he felt that what he was developing and experimenting with was so unique that it warranted protecting. Eventually PSW's sustainer reverted to the more usual electromagnetic driver circuit that some of us have built ourselves. As the whole principle of operation of this device is quite obvious (just physics, the driver is essentially nothing more than a back-to-front guitar pickup) and in the public domain (via the many publically available patents), I figured that was the reason why Pete decided to move his experiments into the open, and for more people to experiment with it as they saw fit. Some of the suggestions offered worked, some didn't. We ALL learnt along the way by other peoples successes and failures. Some of my suggestions were trialled out and experimented by a few people. As I was posting that information on a public message board, in a thread entitled "DIY Sustainer Ideas" I felt that any information I was freely giving was being offered under the full proviso that ANYONE, either here on this board or third parties on the "outside", could use that information as they saw fit for ANY purpose. I also thought that by offering my help in a thread "owned" by PSW that I was freely helping him develop his product. To put it somewhat bluntly, I was giving assitance and information publically, and I couldn't give a **** how it was used. Personally I am glad and extremely grateful that Pete (and all other regular contributors - Onelastgoodbye, Lovekraft, Col, Spazzy etc) has been generous enough to guide this thread to where it now and provide information along the way in order to build my sustainer. Don't forget also that the information I obtained to build mine is in this very thread. There's absolutely nothing that can't be found in this very public thread that would stop anyone from building a system exactly like mine. And if you can't find it here, there are many other sites around the net that will tell you how. If PSW want's to take the information he's collected over the years and make the next move and potentially develop and market his new-and-improved device, I have absolutely no qualms whatsoever in him doing so with information that I may have contributed in this thread. By freely offering information and discussing our ideas in public, we open ourselves up to the possibility that our ideas and information will be used by others. This is not a private forum. I also regard Pete as the "granddaddy" of this whole DIY sustainer device, and I consider the information I gave in my experiements going to him first and to others if they wanted it. I don't believe Pete wants to make a living out of selling sustainer kits, nor does he want to rip people off by stealing their ideas - his entire perogative for marketing his device is to put a simplified system in the hands of people who couldn't possibly afford the commercial alternatives. Much like many new pieces of software springing up these days, it's an open-source project. Consider it like a piece of uncrippling shareware - You can either chose to pay nothing and get a version with a silly "pay me now" nag screen (the DIY sustainer from the pages in this thread - it'll work, but there's no gurantees how well). You can pay the licencing fee and get the full version of the shareware (Pete's proposed kit - it's ready to go, just follow the instructions). And just like the software equivalent, you can pay the big bucks and get the big manufacturer's version instead (Fernandez = Microsoft). Either way, whether you chose to pay for the kit or not, if you've got a small amount of manual skills at your disposal you can still churn out a DIY sustainer for yourself. Finally, I thank you all for helping me get my sustainer guitar off the ground in the first place. Pete may have sparked the initial interest in me to build the sustainer, but it was many of the other contributors who helped me refine it further. I am grateful to you all. I wish Pete every success with whatever he decides to do with his sustainer project. Cheers, Curtis.

Not quite. I'm using two transformers because I didn't have a proper multi-secondary transformer handy to start with. All I did was use a 240/12V transformer to step down from the mains, and then feed the 12V output into a 240/20V transformer wired backwards - so you step down the voltage and then step it back up again. This yields a secondary voltage of 144VAC, which is then fed into a voltage doubler circuit, giving about 400VDC for the plate supply. The step down-step up technique is quite common, retains your galvanic isolation from the mains (important!), and cheaper than getting a custom transformer made. The only drawbacks are you should never exceed the rated voltage on ANY winding, you can't expect much current from the HT winding (so it's only good for preamps), and you need the space to fit two transformers. The 12V output of the first transformer also feeds the heaters, which are DC regulated for low noise. I'll have to dig out the schematic I was working from and hand draw the modifications I did to build mine - I sorta designed it on the run. Leave it with me for a few days and I'll see if I can draw it up. Fundamentally the third channel was built as is. It's the "clean" channel I added that required the changes. If you want true independant operation (eg separate gain, bass, mid, treble and output controls) you're better off building the X88R as it is presented than building mine.

Be careful here - just because the amp is cathode biased doesn't automatically mean it's operating in class A. In fact given the cathode resistor in your schematic and where it's biased at (25V thru 210 ohms gives 120mA, each tube shares this at 60mA), I believe your amp is running class AB1. Given that the amp supposedly belts out "14W Hifi" it's highly unlikely to be running class A. The class of operation is a function of how "on" the tubes are under no signal conditions, not the fact that it's cathode biased. Check the datasheets for the EL84 for more info. However Geo is right - it is self biasing and you won't need to worry about tweaking it when changing tubes. You may find that your amp will stay pretty clean sounding right up to the point of clipping. The power stage is not likely to clip nicely as it is configured ultra-linear (pin 9 of each EL84 is connected to an extra tap on the output transformer). Most guitar amps run the output stage in regular pentode or triode-connected pentodes, ultra-linear output stages are pretty uncommon and are more a Hifi thing. This may be what you're after, but you could also consider disconnecting the ultra-linear taps and either running the EL84's as triodes (connect pin 9 of each EL84 directly to pin 7), or as regular pentodes (pin 9 is connected to the plate supply via a dropping resistor, say 100R-1K 5W - The schematic for the Vox AC30 shows the placement and value of a suitable screen resistor). Some of these tweaks may make massive changes to the way your amp sounds, especially under high volume, so experimentation is recommended!