Sustainer Ideas

[col]

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...

"a bunch of spare THAT2181" lol. Lucky b******

You definitely really SHOULD re-explore the AGC system on your setup with those!

Do you have the sil package ? that would be really nice.

EDIT:

Would you use another THAT chip (I don't remember which one) to rectify the control signal, or just an op-amp based full-wave rectifier ?

I found it... THAT application note 100a shows a 218x with an 'RMS detector' and what looks like standard op-amp based rectification. I'm sure we've discussed this app note somewhere on this thread in the past, but as you have the chips - I thought I'd bring it up again

---------------------

I pulled apart an old SONY tape recorder recently and it had two chunky matching ICs that I would guess do everything. By the look of the heat sinks on top they were power amps, however, they had *loads* of pins and there wasn't any thing else on the board that looked a likely candidate for the agc that is usually found on tape recorders with built in mics. Annoying thing is I can't find a datasheet anywhere... any ideas ? part number is MITSUMI MM1315B

EDIT2--------------------------------

Just discovered that I can buy a THAT 4301P in a DIP (oh yeah baby) package for £5.85 (minimum purchase of 2)

Sounds expensive, but that baby has the VCA, the RMS detector and 3 op-amps all built into the same chip, so its not such a bad deal really.

Lots of other goodies as well.... bit of a bummer that the most suitable one for a 9v battery driven sustainer is in SOIC packaging so impossible(near as damnit) to solder by hand... it has an additional built in voltage reference buffer!

cheers

Col

Edited December 19, 2007 by col

[curtisa]

"a bunch of spare THAT2181" lol. Lucky b******

You definitely really SHOULD re-explore the AGC system on your setup with those!

Do you have the sil package ? that would be really nice.

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.

I found it... THAT application note 100a shows a 218x with an 'RMS detector' and what looks like standard op-amp based rectification. I'm sure we've discussed this app note somewhere on this thread in the past, but as you have the chips - I thought I'd bring it up again

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.

I pulled apart an old SONY tape recorder recently and it had two chunky matching ICs that I would guess do everything. By the look of the heat sinks on top they were power amps, however, they had *loads* of pins and there wasn't any thing else on the board that looked a likely candidate for the agc that is usually found on tape recorders with built in mics. Annoying thing is I can't find a datasheet anywhere... any ideas ? part number is MITSUMI MM1315B

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.

EDIT2--------------------------------

Just discovered that I can buy a THAT 4301P in a DIP (oh yeah baby) package for £5.85 (minimum purchase of 2)

Sounds expensive, but that baby has the VCA, the RMS detector and 3 op-amps all built into the same chip, so its not such a bad deal really.

Lots of other goodies as well.... bit of a bummer that the most suitable one for a 9v battery driven sustainer is in SOIC packaging so impossible(near as damnit) to solder by hand... it has an additional built in voltage reference buffer!

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.

[newfuturevintage]

Hi all--

been playing around a bit with the limiter and decided to take a step back and take some measurements with the coil attached instead of either a speaker or a resistor load. The coil is the brass / steel assembly pictured a page or two back. Measures 5.2 ohms DC resistance. Works reasonably well too.

After connecting the scope, the trace looks like this (scope in parallel with the coil):

Oh my. That can't be good. It was a reminder to me that while testing with a resistor or a speaker is a good thing, it's not the same as testing with the actual coil that's going to be used. It's also a good illustration of the importance of a zobel network on the output of the 386. (I'm using a 5.1 ohm resistor and a 47nf cap)

So, on the scope, this is the output of the 386 with the zobel:

Just thought I'd share, now back to playing with the compression for the coil...

[curtisa]

After connecting the scope, the trace looks like this (scope in parallel with the coil):

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?

[newfuturevintage]

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?

Hi curtisa--

For bypassing on this shot, there was a 10uF electrolytic in parallel with the power supply, and .1uF metal film from the bypass pin (7) to ground. The trace was a bit worse without the .1uF, and without the 10uF, from battery it was a little worse still, and from an AC-DC supply, it was ridiculously all over the map.

I'm convinced you're right on the fizzy bleed. I've had little smokey amps for a half dozen years or so now. they're 386 driven, and running at or close to 200 gain (don't remember at the moment). The ramp-up and fall off of the fizz induced by the coil into the guitar's pickup in my system sounds exactly the same as the smokey when playing soft to hard and letting a note decay naturally. I think the trick is to keep the 386 from distorting, hence looking into the vactrol for limiting. Or finding a different driver amp that's got a touch more headroom.

[col]

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.

These each have thirty pins which made me think 'more than just power-amp'... they are also the only ICs on the main board.

I have seen other ICs that do-it-all for small cassette recorders. Basically you get pre-amp, AGC and poweramp all-in-one... such a shame that that tech is now ancient history (from a sustainer point of view only of course )

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.

Thanks, thats a really generous offer... I will say no right now because I can't promise to actually get around to using it - I have plenty of other sustainer related TO-DOs on my list. But if you do get around to implementing something and it works out well, I'd definitely be up for replicating it. I think one of the biggest things that has held up development is that everyone has gone their own way - so none of the different approaches have been thoroughly tested.

I've been looking again at some of those THAT app notes, and theres one really interesting thing that I didn't notice last time I read through them...

A couple of the circuits use a 'nonlinear capacitor'... its basically a fancy pants op-amp circuit that behaves like a cap with a value that changes with frequency. This means you can have a fast response at higher frequencies without the annoying distortion at lower frequencies - Seems like it might help to improve the response speed in the higher register - the low end stuff is responsive enough already on my setup, but if I reduce the attack/decay times any more I start getting distortion on the low E string.

Oh my. That can't be good. It was a reminder to me that while testing with a resistor or a speaker is a good thing, it's not the same as testing with the actual coil that's going to be used. It's also a good illustration of the importance of a zobel network on the output of the 386. (I'm using a 5.1 ohm resistor and a 47nf cap)

All you need to deal with the parasitics is decoupling cap(s).

As you have discovered, it is best to have a very small cap and a larger cap in parallel. I'm not sure why this is, but it's something I've read in different places - one of those areas where practical devices can't quite match theoretical ones, so you need to learn some 'tricks' I guess.

The zobel will help there, but thats not its only purpose, so you shouldn't be choosing zobel values just to remove parasitics. The zobel is also there to "compensate for the rise in impedance at high frequencies due to the inductance of the voice coil. The goal is to try to keep the load seen by the crossover circuitry as resistive as possible".

Now this is an area that I've spent a bit of time reading up, because my intention is to try and take some of the guesswork out of driver design... If we can measure the inductance factor of the core material, we should be able to tailor the driver to be more efficient over the guitars spectrum. This will include calculating 'correct' zobel values. The idea is that if we use heavier winding wire, we can have more turns... the DC resistance for an 8omm impedence coil will be lower, because the inductive reactance will be higher. The downside of going this way is that the zobel becomes more critical as the driver load becomes more reactive. the upside is that the driver is more efficient... (or at least more powerful?).

My theory (may or may not turn out to be correct) is that Pete arrived at the 0.2mm wire 8ohm resistance coil as 'best' because thats about as big an inductance you can get while maintaining a mostly resistive load over the guitars frequency range.... If you search the thread, you'll find some of the posts I made discussing this and pointing out where it fits in with some people having more success than others at different frequencies... I reckon its down to core material giving the drivers higher/lower inductances with the same wire and number of turns...

Ideally we'd have a 'cookbook' style set of instruction for people to:

#1 test the different core materials they have to hand

#2 choose the best one and calculate it's 'inductance factor' by plugging values into a simple formula

#3 calculate the optimum wire guage and/or number of turns again by plugging into a formula

#4 construct the driver, then measure its inductance (because its bound to be some way off the intended value)

#5 calculate 'correct' zobel values to adjust for the reactance.

If we can do this, then everyone will be able to get much closer to the same 'quality' of sustainer functionality.

The current situation is that we choose the dimentions and material for the core by almost total luck - the only thing we know for sure is that it has to be something that is easily attracted to a magnet.

If we have a more standardized approach to driver design, we can more easily judge the true merits of the different circuits out there and also how different permanent magnets effect the final outcome. As long as someone can post the specs of their coil (reactance, resistance, inductance) then we can adjust the relative success they have with a circuit.. basically we know how much of the success/failure is down to the driver.

I'm convinced you're right on the fizzy bleed. I've had little smokey amps for a half dozen years or so now. they're 386 driven, and running at or close to 200 gain (don't remember at the moment). The ramp-up and fall off of the fizz induced by the coil into the guitar's pickup in my system sounds exactly the same as the smokey when playing soft to hard and letting a note decay naturally. I think the trick is to keep the 386 from distorting, hence looking into the vactrol for limiting. Or finding a different driver amp that's got a touch more headroom.

This is a conclusion we came to many moons ago

At the same time as I started to understand this, one of the other contributers posted that he got his best results by backing off the gain of his fetzer/ruby... he could get rid of most of the fizz before the gain was so low he started losing sustain.

My last circuit was designed specifically to keep the maximum output level just under the clipping level of the LM386. The LM386 is run at minimum gain of 20, the input is conditioned to keep it under clipping level. It was designed as a simulation, but turned out to be so accurate that if the battery is over 9V (new alkalines are often around 9.5v), there is some subtle fuzz. As soon as the battery drops below 9v, its all as clean as a whistle.

There are some obvious issues raised by this no clipping requirement:

It is going to be very difficult to build a sustainer with a LM386, 9v battery and no AGC that can sustain all strings but produce no fizz/fuzz. For this, the driver will have to be very efficient.

Even with an AGC, there are still problems. The response time of the AGC depends a lot on the maximum drive of the system. The stronger the drive, the more responsive the sustain will be.

My current conclusion about my own system (this changes often:)) is that the fairly slow response is mostly not down to the circuit. I think that if the driver is more efficient, the response time will drop dramatically. Thats what started me on this 'understanding the driver' quest.

I have concluded through working with FEMM that my 'bi-longitudinal' dual core driver - while very quiet and switch pop-free - is an inefficient way to drive the strings. A single core driver *should* be better as long as we can control the EM field. I think that this can be done by extending the core from an | shape to a |_|_| shape (tends to be referred to here as a 'cage'). There are differences in intent and also subtle but important differences in construction when compared with a cage intended for 'shielding'.

(EDIT: important note! in the |_|_| configuration the magnet would be between the centre | and the outer |__| - its important that the centre | has opposite polarity to the outer ones)

Extending the core in this way should increase the efficiency of the driver and at the same time focus and contain the field... IIRC think it also increases the inductance and makes the driver more reactive - bringing us back again to the importance of the zobel network (possibly why other attempts at using a 'cage' have not had much success). It is unfortunate that this is not compatible with a pickup mounted 'piggyback' driver. It's also unfortunate that it is completely incompatible with a rail style dual core driver because this lead to a failure of my first foray into 'cages' causing me to dismiss them unfairly at that time.

There are lots of other things that I am meaning to go back to and re-consider - particularly harmonic mode related stuff, but at this stage, I feel that the two most important things are to:

#1 Improve the efficiency and DIY potential of the driver through better understanding and a repeatable design process.

#2 Find a way to simplify the circuit while still retaining a good quality AGC

hmm, time to end this mammoth post. Keep it up guys - I'm starting to get my enthusiasm back, I might even build up enough momentum to actually break out the soldering iron soon - lol

cheers

Col

Edited December 21, 2007 by col

[Captainstrat]

Help! I know I made several mistakes in wiring up this circuit, could someone please point them out to me and show me the correction? Thanks!

Yep, that's one driver, one neck pickup (Virtual Vintage 2.1), one middle pickup (Virtual Vintage Blues), one bridge pickup (Virtual Vintage Heavy Blues) and an extra pickup (HS2) wired out of phase to the amp circuit so it's in series with the Heavy Blues to provide a hotter signal to the circuit. Looks like a H-S-H configuration, plays like a S-S-S in non sustainer mode and like a Humbucker in sustainer mode ... or at least in should. What I'm currently getting is a dull sould in non sustainer mode (real ugly when you use that tone control); and a lot of radio-like whine in sustainer mode...tap the 4PDT switch a few times and I get a bright humbucking sound and no sustain...

[col]

What I'm currently getting is a dull sould in non sustainer mode (real ugly when you use that tone control); and a lot of radio-like whine in sustainer mode...tap the 4PDT switch a few times and I get a bright humbucking sound and no sustain...

If 'tapping' a switch a few times (I assume you mean physically hitting the switch?) makes a difference, then it sounds like at least some faulty soldering or even bad components.

Maybe the diagram is good, maybe not, until you fix the wonky implementation, you won't know for sure.

If possible, its best IMO to post circuit diagrams in true schematic format rather than the kind of ad-hoc 'easy' wiring diagrams you get with diy kits... otherwise there can be ambiguities about connections (not all functionally equivalent switches are physically the same - sometimes the pins are in different arrangements! sometimes its not obvious what is connected to what e.g. in your pic, the 'hot' wire from the bridge pickup comes in contact with the 'power source', it then goes into the 'amplifier board' and loops back terminating in what looks like a connection to earth... theres a dashed line from the amp board to the mode switch, what doeas that mean - it's certainly not standardized electronics notation )

Have you verified that everything works when you set it up as a basic 1 bridge pickup + sustainer driver system ?

That is the first thing to do.

If you've done that and also checked that all the other components are functional, one thing you might want to try is 'continuity' testing the circuit while switching between different modes. For each mode, make sure that all parts of the circuit that should be connected are connected, and that parts that should not be connected are not.

A good place to start would be testing the neck and middle pickups. When they are switched out (supposedly), are they really out of circuit?

Is there an unintended connection between their common ground and the ground of the other components ?

Is there an unintended connection between either of their +ve wires and any of the other components ?

once you've fully tested the mid and neck pickups, how about testing that the bridge pickup is connected to what is should be when it should be (and not to anything else)...

You should be able to use any basic multimeter for this task.

Working this way you should help you discover any errors you may have made constructing the thing and also any design errors you might have made. Even if this doesn't get you all the way to a working system, it will certainly allow you to verify which parts of the switching and wiring are functioning correctly.

good luck

Col

[Captainstrat]

What I'm currently getting is a dull sould in non sustainer mode (real ugly when you use that tone control); and a lot of radio-like whine in sustainer mode...tap the 4PDT switch a few times and I get a bright humbucking sound and no sustain...

If 'tapping' a switch a few times (I assume you mean physically hitting the switch?) makes a difference, then it sounds like at least some faulty soldering or even bad components.

Maybe the diagram is good, maybe not, until you fix the wonky implementation, you won't know for sure.

wiggling it a bit too ...

If possible, its best IMO to post circuit diagrams in true schematic format rather than the kind of ad-hoc 'easy' wiring diagrams you get with diy kits... otherwise there can be ambiguities about connections (not all functionally equivalent switches are physically the same - sometimes the pins are in different arrangements! sometimes its not obvious what is connected to what e.g. in your pic, the 'hot' wire from the bridge pickup comes in contact with the 'power source', it then goes into the 'amplifier board' and loops back terminating in what looks like a connection to earth... theres a dashed line from the amp board to the mode switch, what doeas that mean - it's certainly not standardized electronics notation )

I'll try ... this was the one schematic simple enough for this simple mind to comprehend ...that being said, the original of that schematic isn't too clear as far as where the bridge pickup's ground is supposed to connect ... me think that's the root of my tone problems.

Have you verified that everything works when you set it up as a basic 1 bridge pickup + sustainer driver system ?

That is the first thing to do.

Yep - with a simple driver / mid pickup / bridge pickup config I got my brights in non sustainer mode and some sustain in sustainer mode ... (not bad considering that my prototype driver was built using too thin a wire - .160 instead of .2 and using hot glue instead of PVC glue for potting) ...I'm taking a second stab at the driver, using .2 mm (32 AWG) wire and carpenter's glue.

If you've done that and also checked that all the other components are functional, one thing you might want to try is 'continuity' testing the circuit while switching between different modes. For each mode, make sure that all parts of the circuit that should be connected are connected, and that parts that should not be connected are not.

A good place to start would be testing the neck and middle pickups. When they are switched out (supposedly), are they really out of circuit?

Is there an unintended connection between their common ground and the ground of the other components ?

Is there an unintended connection between either of their +ve wires and any of the other components ?

once you've fully tested the mid and neck pickups, how about testing that the bridge pickup is connected to what is should be when it should be (and not to anything else)...

You should be able to use any basic multimeter for this task.

Working this way you should help you discover any errors you may have made constructing the thing and also any design errors you might have made. Even if this doesn't get you all the way to a working system, it will certainly allow you to verify which parts of the switching and wiring are functioning correctly.

good luck

Col

I'm giving it all another stab after work ... thx Col!

[gaul23]

Hi, I'm new to this sustainer topic.

I actually have the Fernandes 401 kit in front of me and I am trying to figure out how it works.

Does anyone know what the transformer is doing in the circuit on the underside of the board?

Thanks

James

I might not answer your question... The transformer may be a signal splitter (like this circuit: http://www.jensen-transformers.com/as/as014.pdf ). A signal splitting transformer would send the listening pickup's audio signal to two outputs, while ensuring that the two outputs cannot see one another. If the two outputs could see one another, they might communicate with one another instead of communicating with the listening pickup as you intend.

Here's how i'm hoping to build my sustainer:

1) Unaltered guitar pickup circuit (Strat).

2) Short guitar cord from the guitar jack to a box clipped onto the guitar strap.

3) Inside the box, a signal splitter like above. Input from the guitar listening pickup. One output goes to a jack, connected to an amp by a guitar cord. The other output goes to the Fetzer/Ruby connected to the driving pickup.

4) Driver pickup taped in position under the strings. (driver must be very thin.)

Advantages:

1) Guitar not altered.

2) Sustainer can be swapped to another guitar in 2 minutes.

3) Amp gets a clean signal.

Disadvantages:

1) ??

(I haven't gotten the driver pickup to work yet, so i've no idea what other problems might pop up.)

[col]

...The transformer may be a signal splitter (like this circuit: http://www.jensen-transformers.com/as/as014.pdf ). A signal splitting transformer would send the listening pickup's audio signal to two outputs, while ensuring that the two outputs cannot see one another. If the two outputs could see one another, they might communicate with one another instead of communicating with the listening pickup as you intend.

Thats certainly one possibility.

It may also be just to isolate the driver signal rather than to split it....

another alternative is that it could be to in some way tweak voltage/current to make the driver more efficient....

No-one seems to have a definite answer.

Of course, there is one big problem with using a transformer - it adds more EMI to the system, any setup using a tranny will have to be very carefully designed, and the positioning (angles and distances) of the transformer from the pickup will be crucial.

Here's how i'm hoping to build my sustainer:

1) Unaltered guitar pickup circuit (Strat).

2) Short guitar cord from the guitar jack to a box clipped onto the guitar strap.

3) Inside the box, a signal splitter like above. Input from the guitar listening pickup. One output goes to a jack, connected to an amp by a guitar cord. The other output goes to the Fetzer/Ruby connected to the driving pickup.

4) Driver pickup taped in position under the strings. (driver must be very thin.)

Advantages:

1) Guitar not altered.

2) Sustainer can be swapped to another guitar in 2 minutes.

3) Amp gets a clean signal.

Disadvantages:

1) ??

(I haven't gotten the driver pickup to work yet, so i've no idea what other problems might pop up.)

here are a few problems you may have to solve:

# The lead from the amp back to the driver will be carrying a pretty hefty signal and will produce a fair amount of EMI. it will be difficult to stop some of this getting to the pickup, particularly if the lead is going close to the pickup. One thing you might want to look into for this is 'inter-8 weave' wire - this is designed to prevent magnetic radiation as well as electrical radiation - the commercial stuff has a sheild of some high mu material. I made my own though by looking at the diagram on that web-page . It's actually pretty easy to make, and should help to reduce magnetic radiation.

# Driver must be very thin - depending on your intentions, this might be a bigger problem than you realize!

Pete's driver is very thin, but in one way it is not thin at all ! Pete's driver is not a complete driver it is just a coil and partial core - it relies on the core and permanent magnet from the pickup it is attached to - without these it is not functional.

Making a driver that piggybacks a pickup and is also stable and easy to swap in and out quickly will not be a trivial task.

Making a stand alone driver that is thin enough to sit beneath the strings on its own and still has enough power to sustain will be much more difficult - it will probably require special materials for the core (nickel steel alloy with high permeability) and a custom permanent magnet (rare earth, but not a load of little ones in a row, it must be a single bar or the flux won't get to the strings!)

# 'packaging' the system so that it looks good, works well and is mechanically robust (even when jumping around) will be tricky. Using tape for experimental stuff is one thing, but when you've completed the project and you're happy with the functionality, you're going to need something a bit more permanent than a roll of tape to mount the system. Personally I'd want it to look good as well, but thats a subjective issues I suppose. Strap mounted boxes are a total pain in the behind!

I would urge you to first build a simple sustainer system with 1 driver, 1 pickup and a simple on board circuit. That way you will get a feel for whats possible without raising your expectations too high. When you have this working, you can extend it - maybe try a long cable and box the circuit to see if this works as well/better/worse.... then you can try building a thin driver and again compare the functionality...

Good luck and please post your results and thoughts.

cheers

Col

Edited January 3, 2008 by col

[gaul23]

Two drivers built so far..

One is an old single-coil pickup with all the wire replaced with 30gauge magnet wire (9 Ohms). The other is a homebrew ugly thing (8 Ohms of 30gauge wire + rare earth magnets). They are behaving similarly. When plugged into the speaker-out of a cheap stereo, they each can power an acoustic guitar to a create sound apparent at 5 feet. The stereo must, however, be turned up to 50% of full blast to get this volume from the driver -- I find 10% of full blast adequate for casual listening when the speakers are connected.

Are my drivers underperforming?

[Captainstrat]

I'm just about to throw in the towel ... the Dimarzio HS2 is a whispy POS compared to the Virtual Vintage Heavy Blues...and I'm still getting a dull, lifeless tone in non sustainer mode...and in spite of rewiring the driver with .2mm (32 AWG) wire and potting with wood working glue ...still no sustain!

Sigh, I'll see if I can't strip things down to the bare bones minimum...I really don't want to have to replace the Heavy Blues with a full sized 'bucker ... see if the driver/VV HB combo on its own yields the anticipated results ...

Questions: the 4PDT switch is used to take the unused pickups (hot & ground) out of the circuit; as well as to disconnect the battery; thus where does the bridge pickup's ground connect to?

I'm just trying to reason through this: if you connect the bridge ground to common ground; in sustainer mode the amp circuit's (-) also connects to the common ground (or is that wrong?); could that explain the load down sound I'm getting?

Would connecting the bridge pickup's ground to the amp circuit only solve that problem?

[col]

Two drivers built so far..

One is an old single-coil pickup with all the wire replaced with 30gauge magnet wire (9 Ohms). The other is a homebrew ugly thing (8 Ohms of 30gauge wire + rare earth magnets). They are behaving similarly. When plugged into the speaker-out of a cheap stereo, they each can power an acoustic guitar to a create sound apparent at 5 feet. The stereo must, however, be turned up to 50% of full blast to get this volume from the driver -- I find 10% of full blast adequate for casual listening when the speakers are connected.

Are my drivers underperforming?

Its impossible to say from the information you have provided.

30gauge is ambiguous, there are different numbered gauge standards - which one is this wire using?

in SWG, 30 is 0.315mm in AWG 30 is 0.254... that 0.06 can make more of a difference than you might think!

What Impedence does the amp expect to see?

How much current can it supply before it craps out?

What material did you use for the driver cores?

Acoustic strings use an alloy that is less magnetic than electric strings, so test with an electric.

Subjective perception of the sound level should no be trusted - particularly at such close range

I'm sorry to say that '50% of full blast' is meaningless without knowing the specs of the amp, and even more so when compared with a subjective notion of '10% of full blast' being 'adequate for casual listening'.

It's difficult to say if your drivers are under performing, but it should be easy enough for you to find out which one works best. setup one of the drivers and tweak the controls so that one (choose any single note - damp the rest) note on one string is only just sustaining. Any lower on the volume and sustain is lost!.

Then swap drivers making sure that the position is the same and that the distance from the strings is *EXACTLY* the same (as precise as you can within 0.1mm if possible!). if the second driver needs extra volume before it will sustain your chosen note, you know the first is better - conversely, if you can lower the volume for the second driver and still get sustain, you know it is the best.

There are of course caveats. One driver may be better at some frequencies but worse at others. Also, this will only tell you which one works best with the amp you are using - so don't make assumptions based on a cannibalized 'cheap' stereo.

The main thing is that it IS working

The next step would be to construct an amp circuit for your driver - if you use one of the common designs like the fetzer/ruby, you will soon find out how your drivers are performing when compared with the results of other intrepid sustain seekers.

I'm just about to throw in the towel ... the Dimarzio HS2 is a whispy POS compared to the Virtual Vintage Heavy Blues...and I'm still getting a dull, lifeless tone in non sustainer mode...and in spite of rewiring the driver with .2mm (32 AWG) wire and potting with wood working glue ...still no sustain!

Sigh, I'll see if I can't strip things down to the bare bones minimum...I really don't want to have to replace the Heavy Blues with a full sized 'bucker ... see if the driver/VV HB combo on its own yields the anticipated results ...

Questions: the 4PDT switch is used to take the unused pickups (hot & ground) out of the circuit; as well as to disconnect the battery; thus where does the bridge pickup's ground connect to?

I'm just trying to reason through this: if you connect the bridge ground to common ground; in sustainer mode the amp circuit's (-) also connects to the common ground (or is that wrong?); could that explain the load down sound I'm getting?

As the bridge pickup never needs to be completely out of circuit, you connect its ground wire to common ground.

Depending on the design of the sustainer amp circuit you're using and the pickup, you will get different levels of loading.

Assuming that the input impedance of the circuit is nice and high, the loading shouldn't be too bad - particularly when the sustainer is switched off. It may be that you are very sensitive to small changes of this kind, in which case you should consider adding a buffer to your circuit - this will give you a tone that is better than before - better than with no sustainer circuit! there is a downside though - if your battery runs out, you get no sound from your guitar.

Make sure that your guitar cable is in good condition, high quality and as short as possible - this may counteract the loading effects somewhat.

If the sound is *really* bad - so that a non guitarist could tell the difference, then maybe there is something wrong with the wiring or the circuit - a bad component or some such. How old were the capacitors that you used ?

Would connecting the bridge pickup's ground to the amp circuit only solve that problem?

If you don't have the bridge pickup ground connected to the common ground leading back to the shielding on the cable (assuming theres no fancy isolation circuitry), the sound quality will be terrible.

don't give up

cheers

Col

[curtisa]

I'm just about to throw in the towel ... the Dimarzio HS2 is a whispy POS compared to the Virtual Vintage Heavy Blues...and I'm still getting a dull, lifeless tone in non sustainer mode...and in spite of rewiring the driver with .2mm (32 AWG) wire and potting with wood working glue ...still no sustain!

Don't forget that the amp you're driving the sustainer with needs to have sufficiently high input impedance to prevent loading down the source pickup. That could be the reason why you're experiencing such a dull sound - the amp is loading down the pickup signal making it much more weak and muddy sounding. This will also affect the amp's ability to effectively drive the sustainer, which could account for your lack of sustain.

With any circuitry designed to interface with a passive guitar signal there should always be some sort of buffering in place at the input of the amp, something with an input impedance >1M ohm will do. Simplest one I can think of is a JFET source follower run off the 9V sustainer amp battery supply. Maybe a buck or two of components. Google should turn up a few schematics.

[psw]

There are a few people who have been in contact, and I have been a bit busy, so I have missed posts. As always, people are reluctant to try the basic formula and underestimate it's importance...also, they are too ambitious going straight to installation before testing outside the guitar and trying to use the fetzer part of the circuit for a dual purpose guitar buffer and sustainer...amongst other things...

The bottom line for me is that this was designed to run from a small LM386 amp and there really is no excuse for trying it out with HiFi amps, computer speakers and the like and expecting performance...or even effect...and then looking to the driver for the explanation.

The point of this thread was to help people get there...not try to troubleshoot failed installations so much.

My advice has been consistent. Make the device and circuit as specified (0.2mm wire especially) and test it with the bridge pickup over the strings...preferably with the other pickups cut out, or even removed from the guitar. Make sure the thing works... If any doubt about the circuit, test with a speaker to see what is coming out of it.

The, install and add back the other components according to a plan. Before that though, pictures and a drawing of the plan here is a good idea.

In a recent installation BTW, I found that a volume pot of 1Meg or more was excellent for the guitars tone and to open up the signal to the circuit. I used a 2Meg Audio on the last one and it sounded great and the taper was fine...worth a try for the cost of a pot...

Some of these problems are classic loading problems. Using any Hi Fi am has potential problems due to loading as well...acoustic guitars, although they work...have the problem that the bronze is not magnetic so can only work on the internal steel...the d string is particularly problematic then, for the same reason that the high strings can be hard to drive...

Stick at it and return to the essentials as the frustration of tinkering with something can be a little much. Go back and do one thing at a time and you will find the problem and be away...

As for my progress...I am still trying to get my head around the whole installation process....I did a nice 2 pickup guitar recently...but I am having trouble with a typical strat. If anyone has their own ideas of how this could work out please let me know or post here. I am on the verge of attempting digital switching as the whole "nest of wires" to the 4pdt switch worries me...anyone with ideas or links to achieve this...same also...

pete

[Wish1527]

hi to everyone!

first post in this forum and in the EPIC sustainer thread!

i followed this topic for ages, and now here i am trying to contribute somthing!

hi psw! can i suggest this schematic for switching in a 3 pickups guitar?

( hope is not too large and that everyone can understand it )

this was made using a 4pdt switch

the snapshot of my circuit show the switch in the "guitar mode", you can see that the driver is shorted, and that

every connection is just like your average strat-like guitar

when you flip the switch

1) the neck pickup is shorted

2) the sustainer circuit is connected to the driver

3) the bridge pickup is connected to the sustainer circuit

4) the sustainer circuit is connected to the battery

you may notice that there's " a large cap " connected from sustainer supply and ground

this is my midnight idea to eliminate pop and clicks ( is a bit late here in italy so please forgive me )

when you connect the circuit the voltage level from the battery have to charge the cap, so it's like a soft start

and when you disconnect the battery, the circuit keep drawing power from the cap, dischargin it in a slow way

so there's not a sudden change in the circuit alimentation

this is also nice because thanks to this slow start maybe the circuit will give you time to " forgive "

the switching of the other components that are changing when you flip the switch

the only drawback that i can think of is that if you are using the neck pickup and switch the sustainer on

you'll be completely shut down because you're shorting out that pickup.......

maybe could be seen as a side effect killswitch?

what do you think? it is madness or could you put it to some use?

thanks again to everyone contributing to this thread!

p.s.

i promised to psw to post some pickup measure but i forgot! sorry psw!!!

i'll do it soon

edit:

i almost forgot!

wiring could be simplified if there's no need to short the driver or the neck pickup

but i made it this way because IIRC when the sustainer is on and the pickup is not shorted

it behave like an antenna/tranformer and there's EMI all over the places, bad bad noises,

something that is not desiderable, maybe the driver can be left hanging open,

if this can be done ( leaving the driver not shorted when in guitar mode )

i think that a 3pdt will suffice!

( i'll start to work on that to see if it's possible, but maybe tomorrow )

goodnight!

Edited January 6, 2008 by Wish1527

[psw]

Hmmm...some very interesting ideas there...wishy!

However...all the pickups are still permanently wired to ground this won't do...when I say disconnected...I don't mean simply shorted out, you need to lift both the hot and ground/cold of the pickups and preferably short them together (not to ground)

You are also using valuable switching power where it is not required...like the driver (although this could be of benefit) and the bridge pickup.

What I have tended towards is lifting everything including the selector and grond and shorting them together, but not to ground, if not required for the system. The bridge pickup is permanently wired to the input of the circuit and so when power is applied, it will turn on. The driver too is permanently wired in...no need to lift it if it is connected to the back end of the circuit when it is off!

The soft start though is neat...I would be wanting to add a jack socket battery disconnect though as I suspect that cap leakage will result in a slow drain on the battery.

In particular though...and the problem I have with a 3 pup guitar is that you have made no attempt to isolate the middle pickup at all! Which is kind of the point right? This, like the neck needs to be completely disconnected, so even in your scheme you are out of switch poles.

Installation on such guitars does get extremely complex and difficult and as none of has done too many, gets the least attention. Hopefully this post will add more towards this vital part of the project. It is probably more important an endeavour than building the "perfect" driver and is where all my attention is presently spent.

I have got a lead on some of this digital switching stuff...does add a bit to the size of the circuit though...but I think it is doable. Am considering a CD4053 triple gang multiplexer x2! This may result in an electronic 6pdt switch and would ultimately be cheaper and smaller than such a switch, if they made one. The other benefit is that it could be used with a simple spdt or dpdt switch...another chip and you may even be able to get a single 3 way to do on off and harmonic functions...other possibilities may include having a pot sweep through the drive and harmonic functions and/or adding a flip-flop to allow the use of momentary switches to trigger the digital switch chips back and forth.

One attraction of working some of this stuff out is the possibility that somewhere down the track, you could replace selectors, maybe even program the wiring scheme of a guitar...but that would be yet another project....hmmmm

In just breaking news...I have started on a bass version using a musicman like copy...should be fun and uses some misshapen coils from the "commercial" thing I am working on. Any thoughts on this would be appreciated...basically I beefed up the output cap from 100uF to 470uF and am going to use some honking great magnets in the stand alone surface mounted driver...it is well on the way with a circuit and coil already built. Quite what the musical application of such a device is, I am not sure...but you could do some synth pedal type effects and maybe even some jazz tones. We'll have to see...I am trying to enlist the services of a real bass player for some input, but I suspect it really is more of a guitar toy...

Otherwise...am working on a few guitars, there is one in the works for a typical strat like guitar with sustainer which will have to have solved all these installation problems. This has a huge control cavity in the back, so is ideal for testing digital switching if that is where I have to go with this.

I am also refining the test-bed guitar...basically a strat with single volume and tone and no pickguard. This allows for pickups to be screwed in under the strings in a universal total route and connected via screw blocks. I even intend to stick a mini circuit board thing to allow the circuits to be designed and tweaked on the actual playing guitar. This guitar was bought to finish the last prototype to a "professional" level and I found it invaluable. Now that I have finished that, this concept will be refined further to test out anything in a playable instrument...nice playing guitar too, shame really...but a good cause...

I may soon have some guitar "building" threads elsewhere in the forum. While I still have a lot to do with this project, I have had a lot of other ideas and have decided that this year I want to explore those a little more than the straight electronics side of threads like this. All of these instruments that I have lined up will have interesting tweaks and be based on cheap instruments. In the last two weeks I have discovered even more about how to take these POS guitars and at least make them a nice guitar to play! Some of the ideas include tuning mechanisms and bridges, so if you are mechanically minded or have a POS guitar you want to mod out...there could be something in there for you!

anyway...hope the new year is good to all...

p-dub

[Wish1527]

at psw

hey! quite a long post!

i do not understand completely what you're trying to do,

maybe because i haven't taken in consideration how many

things you want to control with just a flick of a switch

i've seen your " uber pushpull + 4pdt " switch and i don't

think that my sleepy idea would beat that!

however to solve challenge like this it would be useful to

know just how many switches and pot you want to use and

how many feature you want to control at the same time

for example:

1) you surely have a 5way switch to do the pickup selector duty

2) if it's a strat like guitar you'll have 3 pots ==> there are 3 POTential pushpull pot

3) if it has a pickguard you can add just a swith if you do not want to put too many holes in there

so lets see

we have 3x dpdt and a minimum of one 4pdt, it is a lot of soldering!!

keep in mind that i think about " normal " pots and switches

nothing custom like yours

if you do a list of things that you want to include in your

switching circuit just write it down and post it or send it

so we can work this out! ( just putting out ideas would help i think

, and having a target is always helpful! )

wiring is not so simple, but if i understand what's the goal and

what are my tool to reach it, i find it a nice challenge! given the right

amount of time maybe you can find an analog solution to it!

the next circuit is a slightly improved version

( it takes a 3pdt instead of a 4pdt ) check it out

improved circuit

and i have a circuit that maybe you'll find useful, it uses a push pull

and give you a volume pot when pushed in when you pull it out

it become a tone control ( with vol on max ) sorry for the poor quality

i'll redo that with a decent software soon

push pull volume tone circuit

psw please, if you can explain better what you mean when

you're talking about " disconnecting the middle pickup "?

why you have to disconnect it? you want to take the pickup

out of the circuit to be sure that the middle pu

doesn't receive the driver signal? to avoid bad feedback and squealing?

hummm....

this would be a nice feature to have

maybe shorting it out would be the same?

food for tougth

now i'm really going to bed.......

keep on rock

edit:

afaik

bass sustainer would be a nice addon for many bassplayer

it would add a " fretless " feel if used in the right way

and isn't sustain one of the major issue of fretless bassplayer?

fretless bass + sustainer = gorgeous

Edited January 6, 2008 by Wish1527

[Wish1527]

slight update!

i've done some measurement to my pickups,

to add some data if someone need a coil making cookbook

for my sevenstring i got these

pole piece 5,5 mm wide in the neck, just a bit bigger than 5 mm on the bridge pickup

pole span 65 mm

bobbin width 15 mm

they are humbucker so i have not a cover to do the other measure

for the strat i got

pole piece 5 mm wide

pole span 57 mm

bobbin width 15 mm

clearance from inside bobbin and cover about 1 mm ( a tad more actually )

i got staggered pole piece on my strat

and i noticed that

on the neck pickup the poles are taller than the middle single coil

if i put a sustainer coil of about 1.5 mm under the pickup cover in the neck position

it would make the pickups equal as far as we talk about the pole piece lenght that come out from the cover

so

adding the driver coil in my situation is no problem !

i've upgraded my schematic for the 3pickups switching with tips from psw

here we go

a bit of explanation about the jfet in there

from what i understood there is the need of a complete disconnection between

the pickups and the circuit so i took out the big guns

the switching short out the pickups and connect the sustainer circuit

so that

when the sustainer is ON

every other pickup is shorted and NOTHING would come out from them

for me this could be a good solution

because when you short a coil there's really no more reason to consider it's effect in the circuit

the only thing to remain would be the magnetic field radiated from the pickup magnet

and that couldn't be removed!

but i wanted to take it a step further

so i added the jfet between the pickups ground and the guitar ground

how do they function?

if i remember well JFETs act like a normally open switch

so that if there's no signal at the gate they can be considered like a very small resistor

20ohm? 10ohm? i don't think it will affect pickups operation at all

normally pickups are in the order of Kohm

something thousand times larger than that

but when you turn the sustainer on the battery voltage put JFETs in " closed switch " operation

so you have the biggest resitor you could think about between that coil and ground

somthing like 10^12 IIRC

so it will surely isolate them from the ground

i tryied to keep the number of poles down ( and i used 3 )

so this can be done with a 3pdt switch

and like i was saying in my previous post

if you like to have switch you can stil throw in 3 pushpull to control any kind of modes

your sustainer would need

hope to find a reel of wire to do some coil cooking!!!!!!!

[Captainstrat]

All right! After two driver prototypes, two amp prototypes; one mega mistake in trying to boost the sustainer output and fixing a major grounding problem; I've got the darned thing at a stage where I can hear it trying to sustain and not quite cutting it ... I think string pull's an issue here. I can definitely hear the screwy harmonics and distorted sound past the 15th fret.

I might be stating something that's already been said (or that is an already well-known fact) but string pull and sustain don't work well together ... the clean tone is there in non sustainer mode, now I need to fix pickup height and see if it makes a difference...

[col]

All right! After two driver prototypes, two amp prototypes; one mega mistake in trying to boost the sustainer output and fixing a major grounding problem; I've got the darned thing at a stage where I can hear it trying to sustain and not quite cutting it ... I think string pull's an issue here. I can definitely hear the screwy harmonics and distorted sound past the 15th fret.

I might be stating something that's already been said (or that is an already well-known fact) but string pull and sustain don't work well together ... the clean tone is there in non sustainer mode, now I need to fix pickup height and see if it makes a difference...

What makes you think string pull is the culprit ?

If the string pull from your pickup is enough to have a significant effect on sustainer functionality, then your tone (without sustainer) would have been terrible !

As long as your pickups aren't close enough to the strings to give you 'wolf tones', you should be OK.

There are lots of things that can cause 'screwy harmonics' and 'distorted sound'.

Screwy harmonics:

coil potting not sufficient

parasitic oscillations... caused by

bad circuit design

faulty component(s)

poor layout of system

squealing feedback caused by interference between driver and pickup (most likely)

Distorted sound:

too much gain in the pre amp

too much gain in the power amp

circuit is heavily distorting the signal in some other way

poor layout - e.g. components/cable carrying large signal is close to pickup

driver and pickup combining to form an unintended transformer causing voltage multiplication and clipping

feedback loop between driver and pickup (as above - before the squealing kicks in, you will get a nasty distortion)

These are just the things that come to mind right now. If your system is 'nearly' working, but you're getting squeals and distortion kicking in before there is any decent sustain, then look to your driver and circuit.

Make sure that your circuit is working cleanly by testing with a speaker. When using it with a driver, lower the gain - you might find that you were just trying to use too much?

I remember when I first tried the fetzer/ruby, very low gain settings were required to prevent instability. In my later circuits, I used minimum gain on the poweramp side at all times!

As far as the driver goes, be prepared to build a few!

There are so many driver variables - even if you use the 'standard' specs for wire gauge and turns, you should still try different core materials magnets etc. and also remember that better quality construction will make a big difference.

cheers

Col

[Captainstrat]

All right! After two driver prototypes, two amp prototypes; one mega mistake in trying to boost the sustainer output and fixing a major grounding problem; I've got the darned thing at a stage where I can hear it trying to sustain and not quite cutting it ... I think string pull's an issue here. I can definitely hear the screwy harmonics and distorted sound past the 15th fret.

I might be stating something that's already been said (or that is an already well-known fact) but string pull and sustain don't work well together ... the clean tone is there in non sustainer mode, now I need to fix pickup height and see if it makes a difference...

What makes you think string pull is the culprit ?

If the string pull from your pickup is enough to have a significant effect on sustainer functionality, then your tone (without sustainer) would have been terrible !

As long as your pickups aren't close enough to the strings to give you 'wolf tones', you should be OK.

There are lots of things that can cause 'screwy harmonics' and 'distorted sound'.

Screwy harmonics:

coil potting not sufficient

parasitic oscillations... caused by

bad circuit design

faulty component(s)

poor layout of system

squealing feedback caused by interference between driver and pickup (most likely)

Distorted sound:

too much gain in the pre amp

too much gain in the power amp

circuit is heavily distorting the signal in some other way

poor layout - e.g. components/cable carrying large signal is close to pickup

driver and pickup combining to form an unintended transformer causing voltage multiplication and clipping

feedback loop between driver and pickup (as above - before the squealing kicks in, you will get a nasty distortion)

These are just the things that come to mind right now. If your system is 'nearly' working, but you're getting squeals and distortion kicking in before there is any decent sustain, then look to your driver and circuit.

Make sure that your circuit is working cleanly by testing with a speaker. When using it with a driver, lower the gain - you might find that you were just trying to use too much?

I remember when I first tried the fetzer/ruby, very low gain settings were required to prevent instability. In my later circuits, I used minimum gain on the poweramp side at all times!

As far as the driver goes, be prepared to build a few!

There are so many driver variables - even if you use the 'standard' specs for wire gauge and turns, you should still try different core materials magnets etc. and also remember that better quality construction will make a big difference.

cheers

Col

At this stage I'm tempted to say that either the driver circuit isn't powerful enough or that the bridge pickup's output is too weak, likely why Fernandes uses an actual humbucker in bridge position. The Virtual Vintage Heavy Blues was giving me some sustain, but as soon as I tried to wire it in series with a HS2 (don't ask) the sustain was gone. I tried to blame string pull, but I think I screwed up the "sensor's sensitivity" by wiring a hot pickup with a weaker one.

More and more I'm tempted to just stick a Kent Armstrong PAF in bridge position and be done with it! I'm just concerned I'll lose the Strat sparkle if I do that!

[Lachlandavis]

Im new, and i want to build a sustainer pickup on an old trashed out guitar.

What is the information i need to get started? Theres 230 pages and ive read about 70 of them but i dont want to miss anything, so if someone could help me out. My dad was an electrical engineer and will help me with that side of it.

[psw]

Check the threads linked at the bottom of this post to get a better smaller version on just how to make one...with out the chat and development.

I think the string pull is not an issue...I still don't have a picture of your driver, but if it is on a convnetional pickup, it must be fine...if you put huge honking neodyminum's in there...well you are asking for trouble!

As for pickup strength, obviously, an HB puts out more output and can safely be adjusted very close to the strings...but the original strat had extremely cheap stock Chinese made pickups in them, very low output and lots of chime. I did use a preamp with more gain than the fetzer, but all those sound clips were done with it and there are pics of it on the other threads and the driver making pictorial shows it's pickups revealed.

No...you have to test the circuit as an amp with a speaker to make sure it is working...you may have to have several attempts at making a driver to get a best quality...but even a badish one to specs should work if the instructions are followed.

I note that you have not shown any drawings or photos of what you have done...don't be shy, this really does help. If you are trying out a secret plan (as you were with the fetzer whole guitar preamp/sustainer thing) then you have to expect trouble. The least you can do is just try it stock and from there mod all you like. These kinds of plans are not necessarily bad, some that prove ill advised, obviously seem to be a good idea at the time (much higher hifi amps to drive it...more power does not equal more sustain, or higher powered magnets usually equals less sustain and loss of intonation.

The whole device is one of balance...just enough power, no more...magnetic strength to make it work, no more. It is more an exercise in efficiency and a curious one at that. As a kid I built model planes as a while...my elder brother once said, well, with a big enough engine, a brick would fly...and I guess that rockets prove that too...but they don't handle that well.

I hope you have taken the advice to get back to basics, test the components outside the guitar and worry about the installation later...that is where I am at and frankly, I find it much harder than making the device itself...but I have made an enormous number of failures...I will post a pic of my bucket of duds to show what you have to go through to get "the best" quality and consistency...would give some a laugh and others some heart I'm sure...

pete