Jump to content

Entry for May 2020's Guitar Of The Month is open - ENTER HERE!

psw

Sustainer Ideas

Recommended Posts

Col-

What do the little red X's mean on your schematic with regard to the power input/outputs on the opamps? I assume you are connecting power to them in those locations, or do you not have to?

the little red X's are to show that that op-amp is already getting power - it is part of a dual or quad amp and one of the others on that chip is wired to the power rails

Share this post


Link to post
Share on other sites
Hi guys, not done much new as far as coils and circuits go's yet, not had the time, but i have installed my first sustainer, its the 2x16ohm parallel wired fullsize humbucker

I would say up to now that this is the way to go driver wise. two parallel 16ohm coils will - due to the relationship between, current, coil turns, impedance and magnetic pull - give roughly twice the magnetic force while keeping everything else about the same - so that's twice as efficient !

Unfortunately, my driver was wired in series because I'd not worked this out until a little later.

Since then I've don't a bunch of other pencil pushing that suggests it may be possible to use a wide variety of drivers, and that the success will depend on the circuit used to drive them ! we'll have to wait and see, but all the stories about pickups being used as drivers may be perfectly true, and the idea of using a pickup as a driver just needs some refinement on the circuit side!

Here are some thoughts I've had on this - this is not an area I've spent a lot of time mulling over, so there may be other problems e.g. losso due to temperature etc.

A pickup has a very high resistance, so there will be a very low current through it - maybe 100 micro ohms - when driven by a 9v battery circuit.

However, a pickup has a LOT of windings around it, and therefor a very high inductance - in the region of 2.7Henries

the magnetic pull of the driver is directly proportional to the square of the current (so we lose out there) and to the square of the number of turns in the coil (where we lose on the current, we gain here).

The inductance is also directly proportional to the square of the number of coil turns, so we can look at the ration of inductances and currents and draw some (rough) conclusions about the magnetic pull we might get from that pickup when driven by a small circuit.

my working single coil driver is 7.5ohm and 1.2mH(milli-henries)

my half a humbucker rail is 5.69kohm and 2.9H....

5690/7.5 = 758.666...

758.666.. x 0.0012 = 0.9104... interesting

more interesting is that when I substitute my 8ohm 1.2mH inductor in my simulation with a 5.69k 2.9H inductor, the current through it comes out at about 183microAmps.

2.9 / 0.0012 = 2416.66...

2416.66 x 0.000183 = 0.442

e.g. it gives us about the same magnetic drive as our 8ohm 1.2mH driver does with 442mA going through it (which is lots)

What I'm suggesting is that the loss we get due to the high impedance of the pickup as driver is more than made up for by the increased inductance of that driver.

Downsides:

Major one is that with a big inductor, there is a big discrepancy in impedance over the frequency range of the guitar. (This is the reason (IMO) that Pete ended up with his 'thin' driver config. any more turns of wire or core mass would make it's effectiveness much more frequency dependent.)

Another is that I'm not sure ho well an LM386 is going to work when driving such a high impedance. If it doesn't handle it well, we'll have to find another solution...

It seems that it might be pretty simple to go some way towards solving the first issue with some clever circuitry. This is what Sustainiac call 'current source amp' (I think?)

I have seen it better described on the web as 'current mode feedback'

the idea is that with a tiny resistor after the driver, we can use feedback to 'tell' the amp to work harder (or not) depending on the current at the other end of the driver - so it will balance up the frequency dependency of the system.

Even if we can't use a pickup as a driver, we should be able to use drivers with much higher inductance, therefor get much better efficiency.

In simulations, this works pretty well. Still to try it out for real :D

cheers

Col

Share this post


Link to post
Share on other sites
Hello,

I'm new here. What an awfully complex project you guys have been trying to solve.

Would it not have been easier to clone an existing commercial design?

Probably not.

And it would have been no fun.

And it would have been more expensive than buying one and installing it, so why bother ?

If you really want to build a clone, just download the Sustainiac patents - I'm pretty sure its legal to build one for your own private use?

Good luck though :D

I've heard its not an easy job building a class-d amp from discrete components and getting it tuned and stable - your layout design will be critical...

Oh and how are you going to find out exactly what alloy is used in their driver core? and when you do, where will you source it from? etc. etc. etc.

Edited by col

Share this post


Link to post
Share on other sites
If you really want to build a clone, just download the Sustainiac patents - I'm pretty sure its legal to build one for your own private use?

Good luck though :D

I've heard its not an easy job building a class-d amp from discrete components and getting it tuned and stable - your layout design will be critical...

Oh and how are you going to find out exactly what alloy is used in their driver core? and when you do, where will you source it from? etc. etc. etc.

Patents are intentionally misleading / omit information, so that's not an option.

Designing a layout is just what is avoided when cloning. Just copy the original. Or does it use integrated circuits not available to the public or are they just too small to solder? Anyway the class d amp is just to save power right? Maybe it could be exchanged with something more traditional while retaining the rest of the circuit. The driver core looks like laminated transformer metal. Unlikely to be an issue.

Personally I think building a clone would be rewarding and fun also.

Share this post


Link to post
Share on other sites
Personally I think building a clone would be rewarding and fun also.

You don't have to go that far. All you need is a compressor/limiter, a small poweramp and a driver.

For the poweramp even the F/R (lm386) will do - I use a tda7231A - has a little bit more power.

Pete has optimalized his drivers for these run-of-the-mill (13 in a dozen, we say) ICs. So build according to Pete's instructions and it'll work. No need for phase-compensation or stuff like that. I think my sustainer performs as well as the commercial ones. Not as energy efficient, though. :D

I think that Pete is reluctant to post and endorse a compressor/limiter is because so much tweaking is required. If he says, this is what I use he can expect a 1000 questions about compressors and how to do the setup. Even if you explain it well enough the person has to test with an oscilloscope and design the print layout by himself. For an experienced builder this is not a problem but for the inexperienced one a design is needed that works out-of-the-box.

Even if you clone a sustainiac you have to test it with an oscilloscope. You just can expect to solder everything error free.

Fizz

Share this post


Link to post
Share on other sites
Personally I think building a clone would be rewarding and fun also.

You don't have to go that far. All you need is a compressor/limiter, a small poweramp and a driver.

Fizz

If that setup works, it would be great news! I was wondering about compressors myself and why they have not been advocated more here.

Compressor/limiter

http://www.thomann.de/gb/behringer_cl9.htm

Compressor/sustainer

http://www.thomann.de/gb/behringer_cs100.htm

What's the difference? Is it the limiter I definitely want?

Share this post


Link to post
Share on other sites

This thread has much talk about agc. Compression ratio, threshold, attack and release are pretty understandable to me but how does automatic gain control differ from compression? Might a compression sustainer pedal work by agc? Here's a schematic of boss cs-3, of which I do not understand all that much.

http://www.dirk-hendrik.com/images/cs3.gif

Edited by jporter

Share this post


Link to post
Share on other sites
If that setup works, it would be great news! I was wondering about compressors myself and why they have not been advocated more here.

There have been some contributions by others. But it's logical to see the F/R amp and the driver as step 1 in building a sustainer device.

Inserting a compressor could be seen as the next step to improve performance.

What's the difference? Is it the limiter I definitely want?

Limiting or compressing, both will do.

Using a stompbox makes a lot of sense to me.

A. You could do some outboard testing

B. Out of the box solution

C. Is designed to work on 9 Volts. Small circuitry. Could be transplanted into the guitar.

D. If info/schematics/print lay-out found on the internet it could be cloned. (Here is where the trouble starts)

And we need a design without exotic parts.

The CS-3 is not a good example I'm afraid. No info on the That2159 available. Difficult to buy I guess.

Fizz

Share this post


Link to post
Share on other sites
And we need a design without exotic parts.

The CS-3 is not a good example I'm afraid. No info on the That2159 available. Difficult to buy I guess.

Fizz

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 :D )...

http://media.digikey.com/photos/Analog%20D...M2317-EVALZ.JPG

http://search.digikey.com/scripts/DkSearch...SM2317-EVALZ-ND

Edited by Hank McSpank

Share this post


Link to post
Share on other sites
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...

Of course I want it! Thanks, Hank.

So you caught me telling the untruth. :D

I've been looking for that THAT before, today I did only a quick search and I couldn't find it.

Share this post


Link to post
Share on other sites

AGC is just a general term for something that varies the output volume depending on the input volume.

This can be a compressor, a limiter an expander or some combination thereof.

And we need a design without exotic parts.

The CS-3 is not a good example I'm afraid. No info on the That2159 available. Difficult to buy I guess.

[this isn't a reply directed at Fresh Fizz, just at this discussion ;)]

Yes it is important that we don't use parts that may be difficult to obtain.

FWIW, the THAT2159 is a voltage controlled amp it's not an AGC chip.

You still need to supply it with a control voltage, and thats where most of the work in an AGC is anyway.

e.g. in the AGC approach I've been using, the voltage controlled amp is one op-amp, a FET and a few resistors and the ood capacitor - no big deal really. The complexity is in the circuitry to supply the control voltage - this uses 2 op-amps and a whole bunch of caps resistors and diodes - maybe two thirds of the AGC is to create the control voltage.

There have been DIP package compressor limiter AGC chips in the past, but they went out of production when tape recorders bit the dust.

There was a cracking chip of this type that had two channels of AGC - we could have used one channel as a compressor/limiter to level out the input we wanted to use, and the other channel as an expander (squelch) to kill and input below a threshold to prevent un-tamable feedback from low level signals. Unfortunately this is another obsolete out of production item - it would be crazy to base a new design on something like that.

There were also others that had input buffer, AGC and a power-amp all on the same IC - think 'instant sustainer driver circuit'. Again these were intended for radio cassette recorders and are unavailable these days.

We discussed this whole topic a long time ago in great depth.

Afterwards, a number of AGC approaches and circuits were proposed. The one I ended up with works very well for the purpose. It is maybe a little over complicated, although to put things in perspective, my whole circuit including input, AGC, harmonic modes and output amp is less complex than that cs3 circuit.

Its possible to create a pretty good AGC for our project using 3 op-amp sections, 2 diodes, 9 resistors, 1 capacitor and a FET (give or take a few resistors)

Thats pretty good value and no esoteric parts required.

As for cloning a sustainiac - GO FOR IT. When you get it up and running, it would be great to hear how you got on and see some documentation on how to do it.

cheers

Col

Share this post


Link to post
Share on other sites
Yes it is important that we don't use parts that may be difficult to obtain.

FWIW, the THAT2159 is a voltage controlled amp it's not an AGC chip.

You still need to supply it with a control voltage, and thats where most of the work in an AGC is anyway.

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.

Edited by Hank McSpank

Share this post


Link to post
Share on other sites
Its possible to create a pretty good AGC for our project using 3 op-amp sections, 2 diodes, 9 resistors, 1 capacitor and a FET (give or take a few resistors)

The problem with your design is that fets are not that consistent, specs can vary a lot. That's why I haven't posted my design, based on the Ross compressor. Fet needs to be biased properly, not all ca3080s work exactly the same(bias, transconductance), transistors have different hfes.

What we need is a design where all the calculations can be made based upon component values like with the THATS.

Could be as simple as this one

Looked it up in the dictionary, still think I ment exotic :D

Cheers

Fizz

Share this post


Link to post
Share on other sites
Its possible to create a pretty good AGC for our project using 3 op-amp sections, 2 diodes, 9 resistors, 1 capacitor and a FET (give or take a few resistors)

The problem with your design is that fets are not that consistent, specs can vary a lot. That's why I haven't posted my design, based on the Ross compressor. Fet needs to be biased properly, not all ca3080s work exactly the same(bias, transconductance), transistors have different hfes.

What we need is a design where all the calculations can be made based upon component values like with the THATS.

Could be as simple as this one

Looked it up in the dictionary, still think I ment exotic B)

Cheers

Fizz

My circuit worked as I expected first time with the first FET (J201) I tried.

If you're having trouble, buy a handful (they're pretty useful for all sorts of guitar effects circuits anyway - so worth having a bag full), and go here for a very simple method for measuring their gate-source cutoff voltage (that's what we're interested in here).

If someone isn't willing to put in that amount of extra effort, then this project probably isn't for them, what with all the driver coil construction, magnets to try, selecting and testing core materials etc.

There are loads of tasty JFET based AGC circuits all over the net to experiment with. (Thanks to this latest discussion, I found yet another that looks like a really good bet - might give limiting over a wider range of signal voltages than the others I've seen.)

You ment exotic. I however, meant esoteric :D.

1. Intended for or understood by only a particular group

2. Of or relating to that which is known by a restricted number of people.

3. Confined to a small group

any electronic component that fits the above definitions isn't going to be easy to get and isn't going to be around for long - the THAT chip in question fits nicely :D

Edited by col

Share this post


Link to post
Share on other sites

This is all sounding a little deja vu...in fact such discussions have occured more that twice...

This post from page seven (access by the pink arrow at the top of the quote) shows that LK was as usual getting to much of these points...

OK, now I understand why you've been hung up on the phase issue - I just spent a couple of hours wading through some of the most obfuscated natural fertilizer that the best legal minds in the US can produce, and I'm probably, as the guy in Billy Madison said, "..dumber for having heard it...". :D Let me spend some time digesting it.

It looks like a simple all-pass filter (the basic building block for a phase shifter) should take care of any real-world problems with phase lag (if they actually exist), but of course that wouldn't be patentable, since it would be reasonably obvious from prior art.

The"non-linear square-wave amplifier" touted in Hoover is a Class D (or digital) power amp - it basically pulse-width modulates an ultrasonic signal at a fixed frequency above 40 KHz and passes the result through an integrator to retrieve an audio signal, much the way a one-bit Sigma Delta D/A converter does. Probably overkill for a DIY stab at this, but it could be made extremely efficient.

At any rate, the one thing both patents seem to have in common are the basic signal chain:

<span style='font-size:12pt;line-height:100%'>Pickup=>preamp=>current amp with gain control feedback=>driver coil(s)</span>

I think the trick is in the gain control - you'll need a compressor/limiter so as the string falls into phase lock and the input rises, the driver current is reduced to avoid overdriving the string itself and banging it into the frets. Simply clipping the pickup signal and then lowpassing it might give you enough gain reduction to bring it under control, or you may need active attenuation driven by the output signal. I'd be tempted to try a simple op-amp pre driving a diode clipper in front of one of Ansil's LM386 mini amps to push the driver coil, maybe with a phase reversal switch on the opamp's input, just to see how the simplest possible circuit would perform. OK, enough blathering - I'll try to find a simple phase compensation circuit (just for the sake of argument B) ), and report back.

Oh, just one more question - if you're using a permanent magnet as a core, wouldn't it make better sense to orient the north and south poles vertically, since you're making a electromagnet rather than a pickup? Just a thought, and as always, I could be completely wrong about any/everything, so always check my math. :D

BTW, dude, an excellent job on getting all that together and making it presentable - I know you put a lot of effort into it, and I for one appreciate it! udaman.gif

Page Seven is also known for my post linking a lot of the major patents directly, to which this post refers.

The one thing that proved to be false I believe, was the clipping square wave signal to be preferable to a clean signal...an idea that more than a few of us have thought and tried along the way.

I had forgotten how quickly I jumped into the hex things as well..by this page I was well into this.

Any outboard gear seems to cause a lot of problems...even something like what we were going for in the mid 30 pages proved to be impractical...but beautiful in design...

boxHH2.jpg

Quite a lot of work went into these ideas...I even made mock ups and circuits for Tim's lovely design. The idea was to make all the circuit and battery parts into a kind of tail piece. I even built special knobs and switches for the project. For instance, the drive also activated the sustainer if you pushed down on it with the heal of the hand for sustaining selected notes on the fly. But the wiring (particularly the bypassing) was fairly extensive. This is the aspect that needs to be considered with any outboard gear, remote power or stompbox kind of affairs that people may contemplate.

...

Anyway...not a lot more that I can add to the discussion that hasn't been said, speculated, researched or tried before. Col's circuit also introduced the concept of the "forward feed" compressor (hope I have that right) and the discussions around that are fairly instructive and convincing (in the end) and I believe is expressed in col's design. You are not going to find that in an average compressor.

My attempts at AGC in recent times is a nod to this, but nothing like as sophisticated.

...

As far as cloning a sustainiac...well, it might be possible to build or something similar...this is the direction dizzy took, and although his circuit was never revealed, he did tell me that the driver was bi-lateral (and I saw a picture) and the circuit did have phase compensation (of his own design) and he did reveal that the amp was based on the LM386.

As far as a comparison...LK always owned a fernandes or sustainiac and being a bass player, wasn't really interested in building one but took a very active interest in the thread while he was around. It was his influence, often by personal email, that made me reassess my concerns over many of these issues and concentrate on the driver things.

I did have a brief encounter with an actual sustainiac equipped guitar about a year ago. It worked very well with a very even response, no switch noise concerns, and this one had an extra "mix" control knob that seemed to be some kind of filter that was very effective.

In comparison, mine is a lot more primitive...or at least a different response and sound. The circuit board is at least 4 times smaller and the guitar is completely passive when the sustainer is off (unlike the sustainiac and fernandes). The pickup/driver on mine are also passive and allows greater choice...the size of stand alone drivers such as on my tele can be very small and fulfill the "low mod" criteria that I had set myself.

As LK said above..."Probably overkill for a DIY stab at this"...with a lot of this project, it is a matter of how far you are prepared to go. It was this kind of thing that "turned me" from looking for complex circuitry solutions and concerns and look for other ways...the only thing left was the driver I guess. But that shouldn't stop anyone discussing or building or cloning or doing whatever they desire. Actualy cloning may be hard...there seems to be some protective epoxy on a secondary board on some (maybe the sustainer) and I would assume that there may be SMD's involved.

I have convinced myself sufficiently that it can work without a lot of fuss...but to make it "better" is going to require attention to these kinds of things to get that little bit more of an "improvement". What is actually an "improvement" may also be subjective. There are lots of ways this thing could go.

Installation, regardless of approach is still a much neglected subject IMHO...there should be at least some mind to this aspect I believe.

...

I guess what I have built is a "controlled feedbacker and harmonic generator"...and that's what it sounds like to me. There is a bit of anarchy in there. It isn't as smooth and even as the sustainiac, but then the sustainiac lacks the power of the unrestrained basic version. There are auxiliary reasons for choosing the more basic approach...simpler much smaller circuits, smaller drivers or combos with pickups that add no extra magnetic pull on the strings, more installation options, cheaper costs, lower mods...these were always a concern in my ambitions...but that may not be others...

Anyway...carry on though...

pete

Share this post


Link to post
Share on other sites

Well...it all went suddenly quiet....hope I didn't kill off the discussion...actually I hope that you are all off tinkering away and going to come up with something amazing that will blow me away!

Anyway...still a lot of hits and we have gone well over the 200,000 view mark recently so clearly there is still a little interest

pete

Share this post


Link to post
Share on other sites

Okay, dunno if you remember me from a few pages back, but I got my sustainer working.

I used a bit of steel about 3mm thick, 10mm high, and about 60mm wide. Clamped it in a vice, about halfway, and wound about 150 turns of .315mm wire around it, drenching the thing in PVA glue while i did so. After the glue had dried, I popped a pickup magnet under it, put it in my neck pickup space, and hooked it up to my Ruby amp circuit.

Well, it sustains the A string, and the G, and sometimes the low E. Does anyone know why this is? Something to do with my wire being .315mm instead of .2mm?

Also, I'm getting distortion, acoustically. I'm guessing this is because my circuit's maxed out on gain and volume, so the sustainer coil is distorting the shape of the strings' vibration. How might I go about solving this? If I turn down the gain much, I cant get anything to sustain, not powerful enough, again i suspect its something to do with the wire size. Or perhaps I need this "Fetzer" thing everybody talks about - but I cant find anything about it from googling. Perhaps I need to search these forums, I shall do that in just a moment...

Overall, not bad. About £20 I've spent on this so far, and after reading this thread I was a little concerned it wouldnt work at all. So, as you can imagine, I'm rather pleased so far :D

Cheers,

Akula

Share this post


Link to post
Share on other sites

Ohhh...

after reading this thread I was a little concerned it wouldnt work at all. So, as you can imagine, I'm rather pleased so far

hmmm...

well...you got something out of it. Of course I maintain the need for the 0.2mm wire specs on this design, and your results seem to support that. I'm not clear on the amplification you are using, but the less efficient the coil you need to try and drive the thing harder...my "theory" is that with some specs it wont be able to work fast enough to drive those high strings...but hey, could be wrong on the reasoning, but the results are evident.

The 3mm steel is what I use typically...generally about 3mm deep for hand winding with 0.2mm wire and a suitable magnet attached (like a typical single coil ceramic or equivalent kind of thing.

These photos of my telecaster driver may give the best indication yet of the kind of thing as it shows the essentials of the construction. Of course, I used a method that did away with the bobbins and used epoxy to hold it all together...that's not advisable to try and replicate first off...

th_SMparts7.jpgth_SMparts6.jpgth_teleblue2.jpg

It's a bit more "compact" than waht most will be able to do on their first go...but the design is the same as the original pickup driver that was hand wound with bobbins on a 3mm steel core with a pickup under it and the magnet below that...

PD3a.jpg

or the prototype I made just before that seen here...

driverphoto1.jpg

resting on the strings...the bobbin was made with cardboard in this case! The driver pictorial shows the actual making of the original (see link in signature).

...

Clearly...I believe that the specs for this design are crucial to success. There is enough leeway in there for DIY, different poles and such...but the recipe of 0.2mm wire, thin (say 3mm deep) coil, and well potted with something like glue and wound reasonably tightly and clamped in while drying and wound to about 8 ohms should produce a reasonable to excellent response when coupled with a basic but stable amplifier circuit that does not load the guitar.

It is a balancing act...more efficient drivers mean less power required and less EMI out...running it effectively with the least power should be an aim, if only for battery life, but for all the other potential problems as well. More gain only tends to make things worse...more headroom (clean power) may well be a great advantage.

0.3 over 0.2 is half again or out by 50%...this is not a "DIY tolerance" that this project would accept...but the fact that you got any response at all should give you some hope to try again...

pete

Share this post


Link to post
Share on other sites

Oky. I'll try a design with .2mm wire. I'm also trying to make a scratchplate out of aluminium, so I'll have some of that lying around, which could be useful for making bobbins. Its non-magnetic, so it should be ok, right? The plastic i used for my current driver was taken from the trem cover of this guitar lol, and its not particularly sturdy. And the first driver I made, well, it kinda got clamped a bit too hard when the glue was drying, and it ended up about an inch tall. Oops.

Wire's cheap. I'll try again this weekend

Share this post


Link to post
Share on other sites

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?

Share this post


Link to post
Share on other sites
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?

Yes...we seemed to be having some translation problems...but even with a translator it started to sound weird...a lot of bravado. To the extent even that he posted a circuit, then pointed out that it was full of errors and not actually what he had done. Some interesting drivers as I recall with tin can magnetic sheilding. No audio was presented and he disappeared without trace...as seems often the case! But who knows, perhaps it was perfect and he didn't need to do an more with it.

so I'll have some of that lying around, which could be useful for making bobbins. Its non-magnetic, so it should be ok, right?

Well, you might want to consider eddy currents in any metal, it might not be magnetic, but it is conductive. I have even read that sustainiac strongly advises against such metal pickguards with their more evolved and much envied systems.

And the first driver I made, well, it kinda got clamped a bit too hard when the glue was drying, and it ended up about an inch tall. Oops.

Really with proper preparation, and with not that much practice...it should take 10 minutes to wind a coil as shown in my extensive pictorial on it (bear in mind that this was the first installed version and it took perhaps 15 minutes, but only because I was taking pics at the same time!)

All extensive changes to the basic design, and any flaws in the coil will show up in performance. You don't want to clamp things tight, you want to squeeze the air out, wrap it in tape and hold it there till it is set enough. I am sure it shows that the sides are pushed in every now and again with an ice cream stick or similar just to be sure. The finished coil is protected with tape to hold it in place even though the glue may not be fully set after clamping...

Preparation is the key...no use thinking of these things after you get gule everywhere. How you were able to get something an inch tall when you are winding on a 3mm deep bobbin or blocked up coil I don't know. However, you are free to try your own ways, if it produces a similar result it will probably work...but if you want an "easy" way...follow the instructions before deviating to such extents...and don't be surprised if it doesn't work as expected and then suggest that the device doesn't or couldn't work as I have presented. It's worked for me, it's worked for others...in fact I have had emails of thanks from a couple of people who did the whole thing successfully without ever joining PG, contributing to the threads and with complete success simply by following these guidelines...

0.2mm wire, 3mm depth coil, glue potted neat and non-aerated windings around a magnetized steel core or something equivalent...and a stable non-loading amplifier.

...

Good luck with the Hex circuit...how are the drivers going?

pete

Share this post


Link to post
Share on other sites
Good luck with the Hex circuit...how are the drivers going?

pete

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!

Edited by Hank McSpank

Share this post


Link to post
Share on other sites
Well...it all went suddenly quiet....hope I didn't kill off the discussion...actually I hope that you are all off tinkering away and going to come up with something amazing that will blow me away!

I'm still checking in regularly. I have concluded I need a better driver and so I picked up a bunch of tiny neodymium and ceramic magnets the other night to experient with. I have some steel flatstock to use for a blade and I am in-process with making a nice bobbin, but I am ditching the whole "use a pickup" idea for good.

I did do some testing last week injecting lots of different effects, one by one, into the signal chain to feed the LM386 circuit and see if anything positive would happen. I fed reverb, delay, compression, chorus, phaser, flanger, tremolo, rotary, wah, auto-ya, and envelope filter in, but nothing at all got positive results. Chorus did give a pulsing effect to the strength of the sustain, but nothing useful really.

Share this post


Link to post
Share on other sites

I wanted to play around with PIC programming and such, but learning curve and motivation...and life being too short and complex as time goes on prohibits. I thought that the thing it could really help with would be potential switching problems...and potentially open up other areas of exploration not necessarily sustainer related. They may have some use for complex fequency dependent phase shifting perhaps, or maybe some neat filtery kinds of effects...but the pic is only the brain, it still needs circuitry to control.

Stepping back a little, I personally decided to try and go the opposite direction to sustainiac and things like the Moog...hence my different perspective. Way back (probably about the 30 ish pages) we tried to work out a list of ideals and goals to work towards. The end result was things like low or no permanent mod, less complexity, small size, cost, ability to convert an existing instrument without compromising it, stealthy...I forget the whole list.

This may help in understanding my personal abandoning of the Hex things (that very quickly become extremely complex, the interaction of the magnetic fields and separate hex signals or processing is some of the more obvious factors)...despite some successes in it and being "married" to the idea.

If you look at things like the pickup driver and my more recent tele driver...these fulfilled almost all the criteria that was set way back them and motivated their development. On those criteria, while performance may not be "equal" to the commercial units, they surpass them on the criteria set back then.

The tele driver for instance, surface mounts...except for the rewiring and the hole for the mini toggle on of switch...it has no mods and is reversible. The driver can be seen, but is small and unobtrusive...in the new ultra thin pickup conversions for strats, it is literally invisible and adds no extra magnetic pull and lowers the cost as well!

So...this might help people put into context where I am coming from and my comments. There is nothing wrong with pushing things in different directions, hex designs or multi coil drivers, etc. However, as soon as you remove the neck pickup to put a driver in there, you are diminishing the performance of the stock instrument.

The hex things became quickly apparent that even if I did crack it...it would be well out of the realms of DIY and was becoming very costly to experiment with.

...

Some of the more recent experiments were in control systems. I tried to work out ways to make unobtrusive controls that would operate the sustainer. One of these are what the GuitarNuts2 forum dubbed Uber-switches...hehehe...

switchpot1.jpgswitchpotknob1.jpg

Someone like Donovan may be interested in this idea. These are converted push pull pots. They combine the dpdt push pull function and a 4pdt switch (equivalent to an S1 switch or the kind of switch power required to turn on the sustainer as it stands) and a pot. I even transplanted the guts of a 1k pot into the push pull to get the value required for my circuits drive control.

The result is something fairly stealthy and low mod...certainly no drilling into the front of the guitar!

Of course this is not limited to sustainer control. On my strat (still to be rewired because of the complexity) I have three of these things! The middle control is the sustainer, pot for drive, pull for harmonic and twist the bass (like a car radio thing) to turn it on and off. I still have the equivilent of two S1 switches and two dpdt push pulls in there and two pots! So, the wiring is intended to have a series parralel thing to switch between a strat and brian may like series wiring. I also can add coil splits to the bridge HB and perhaps even phase switching as well. I even have switching let over to add a piezo in there...and all of it virtually "invisible"...

So, you can see how I branched off in more recent times but that the "criteria" that I set myself was in focus throughout and succeeded in one way at an approximation of most of those goals! But other's might have different criteria than mine. I would encourage people to do such a list and really soul search this question though when branching out to keep focus. I certainly feel that I had some "lost years" for not doing it, and if you wanted to be come a sustainer thread "historian" I think you can see where I finally started to see the light...hahaha...though I somehow don't think I admitted it at the time!

pete

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...