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Sustainer Ideas

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Hi everybody,

There's a lot happening at the moment (simulations, hexaphonic pups, new schematics). I like to comment on some of the ideas proposed. But first I show you my sustainer.

I wouldn't advice people with less experience in electronics to build my sustainer. (No print available, need to do a bias setup - with oscilloscope-). Ofcourse I don't mean the hank mcspanks, zfrittz6, col and donovans of this world. Piece of cake for you guys :D

Steady Steed

The schematic

Info 1

Info 2

Cheers

Fresh Fizz

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Hi everybody,

There's a lot happening at the moment (simulations, hexaphonic pups, new schematics). I like to comment on some of the ideas proposed. But first I show you my sustainer.

I wouldn't advice people with less experience in electronics to build my sustainer. (No print available, need to do a bias setup - with oscilloscope-). Ofcourse I don't mean the hank mcspanks, zfrittz6, col and donovans of this world. Piece of cake for you guys :D

Steady Steed

The schematic

Info 1

Info 2

Cheers

Fresh Fizz

Actually, can't count me in that list... I consider my project a failure on hold at the moment. I burned myself out from messing with that circuit and probably won't try another sustainer circuit until I learn A LOT more than I know now. I've been reading this thread on a regular basis, hoping to get up to speed, but Col and Hank are getting into some unchartered waters. With any luck, they'll have it sorted before I break down and buy a Fernandes or Sustainiac system. :D

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Fresh fizz...thanks for posting up all the details of your build.

That's quite an elaborate (Rollys Royce?) of limiters...I wasn't familiar with it, but a bit of Googling certainly shows it's a good 'un - it doesn't suprise me that it works well (a more technical explanation of the circuit is here - http://www.geofex.com/PCB_layouts/Layouts/d&rpub.pdf )

A couple of questions...

1. Why did you choose a 12V rail?

2. What made you choose that particular output chip?

3. You say in your accompanying notes that you circuit really needs a scope to assist setting it up ...is this same scope not helping you eliminate your two string fizz? (in other words, is you fizz not visible on a scope - what does you rsignal look like across the driver if you feed a sine wave into the circuit?)

Edit: By the way...your limiting method 'after' the gain controlled amp, sort of falls into the same trap that I made with my AGC circuit (when I placed it inadvertently in the wrong part of the overall chain)...the CA3080 is essentially acting as a VCA (albeit in this case a 'current controlled' amplifier using pin 5)...the signal at output of the CA3080 is rectified & then fed back into itself on pin 5. In my opinion, the sustainer circuit will work better if the signal is monitored/assessed before the CA3080 & then the gain of the CA3080 altered to suit. Else you'll need to set the whole circuit's gain to cater for the worst case scenario (thin string/high action) & ensure the limiter is set to allow that condition through - of course, this means the thicker, lower actioned strings will likely have too much gain (which could cause probs). I guess the Ross compressor designer didn't have to cater for the fact our input can grow back into a large signal (ie the Ross compressor was designed for a standard decaying guitar signal), hence their decision to limit after the CA3080. Just my opinion of course! (& anyway, you're getting good results, so we can therorize all day long - the proof is in your pudding!). As it goes this Ross compressor circuit has intrigued me sufficiently to pickup a CA3080E chip on my way home today (my first contact with a transconductance opamp!) ...I'll have a tinker with it over the weekend & see how it interfaces with my PIC's AGC output.

Anyway, once again great work (btw: it's too high a component count for me! And perhaps a bit 'high maintenance') ....is that your first sustainer build?

It's fairly quiet my end...I've been plodding on with my CNC build (which is a real time sump too - but it's getting to the stage where I really need it,

to cut acrylic into a suitable shape to hold the multiple single string drivers I have!). Alas, the courier delivering the latest 'Sustainer' project components attempted to deliver twice...nobody home! So I'm kind of stuck for now (hopefully they'll succeed tomorrow which might allow further dabbling over the bank holiday weekend).

This downtime has given me time to ponder how to nail that 'high action' excitation problem (or lack of) & I'm now thinking that one plan of attack of attack is possibly a 'reserve coil' only to be brought into play when the AGC circuit hasn't managed to get control of the string within a set time. I'm now thinking along the lines of a sustainer 'driver' that has three separate coils (ie two strings per coil) & one coil that could be used as backup & which bridges all strings**. I can then use the PIC to decide & enable/ bring the extra firepower online on demand....hopefully the extra coil 'rowing in parallel' will quickly coax the most reluctant high strings into action. Does anyone know how the commercial units perform wrt higher actions? (or is it just a general case of "You want a Sustainer? Then you'll have to tolerate some notes not kicking in if your action is too high")

I've also just sorted my coil winder program out...which up until two night ago, I hadn't realised had a bug, which meant that the winder was miscounting the coil revs! (Oops!). Anyway, I've just wound a corker - 150 turns of 0.15mm wire...1.2mH @4 Ohms ...we'll see how that one performs over the weekend.

** The other option is two coils - one for Low E thru G strins plus a coil dedicated to the High E & B strings - which I'm beginning to think really need 'special' treatment! (especally to coax .009s into excitaition when the action is high)

Edited by Hank McSpank

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Hey guys! I've had all kinds of frustration with winding the driver. I have 32 AWG copper wire, and used a salvaged single coil pickup. Used wax candles to seat the windings in the top 3mm of the coil. And elmer's wood glue to bind it all together and I can't get a reading with my multimeter from ends of the driver. Very frustrating!!! Anyone have a spare driver laying around or be willing to make me one? I will gladly pay for the parts used and shipping! I want to get my hand in debugging and designing but i'm held back by my lack of a driver in the first place!! Grr... let me know guys! ToNy

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Hey guys! I've had all kinds of frustration with winding the driver. I have 32 AWG copper wire, and used a salvaged single coil pickup. Used wax candles to seat the windings in the top 3mm of the coil. And elmer's wood glue to bind it all together and I can't get a reading with my multimeter from ends of the driver. Very frustrating!!! Anyone have a spare driver laying around or be willing to make me one? I will gladly pay for the parts used and shipping! I want to get my hand in debugging and designing but i'm held back by my lack of a driver in the first place!! Grr... let me know guys! ToNy

Sorry I can't help you there... at this stage, I'm only winding smaller one string drivers...at the risk of appearing a little blunt....it's not that tough a task to wind a coil...why not have another go? Next time, I'd say don't bother with the glue ...at least this way, you can always unwind the coil again if it hasn't turned out as you'd imagined (once you're happy - simply pot it with wax afterwards)

Edited by Hank McSpank

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one question, what would happen if i used a home made fuzz factory clone circuit instead of a F/R (or similar) circuit?

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Hey guys! I've had all kinds of frustration with winding the driver. I have 32 AWG copper wire, and used a salvaged single coil pickup. Used wax candles to seat the windings in the top 3mm of the coil. And elmer's wood glue to bind it all together and I can't get a reading with my multimeter from ends of the driver. Very frustrating!!! Anyone have a spare driver laying around or be willing to make me one? I will gladly pay for the parts used and shipping! I want to get my hand in debugging and designing but i'm held back by my lack of a driver in the first place!! Grr... let me know guys! ToNy

Sorry I can't help you there... at this stage, I'm only winding smaller one string drivers...at the risk of appearing a little blunt....it's not that tough a task to wind a coil...why not have another go? Next time, I'd say don't bother with the glue ...at least this way, you can always unwind the coil again if it hasn't turned out as you'd imagined (once you're happy - simply pot it with wax afterwards)

Thanks Hank! Believe it or not you solved my problem! I had no idea that I didnt have to glue it until after some testing, wow! That is awesome, wax potting after testing I can handle! Going to start winding up some more drivers tonight, maybe a plethora of designs might yield atleast one that will work in some scenario. THanks again, ToNy

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So anyway been fallowing this thread for years (on andoff) just figured i might get in on it now. (even though there dosent seme to be much activity anymore) i recently sold a guitar that i did some heavy mods too this guitar was a jackson dk1 performer and it had the fallowing mods

1. pickups replaced with.

bridge-symour duncan nvader

mid-EMG SA

neck custom hex driver/pickup system

2. bluetooth pick sensor (a while back a company came out with a product that could learn your playing via a bluetooth guitar pick with a strap on your wrist that transmitted to a pedal and could tell after you playing a song several times and switching effects on and off when to automatically switch the effects based on the exact hand motions you were making i just built it into the guitar)

3. signal processing circuit to rout the hex pickups to indevidual outs via a parallel printer cord (25 pin D-sub connector)

4. custom sustainer circut base loosly on the research done here which could drive the hex drivers based on frequincy

there was a ton more done to this guitar including custom pain custom inlays and scaloping i would love to both talk about this guitar and get/give ideas on the sustainer progect because im wanting to do the sustainer thing again on one of my other guitars because i love the sounds and no i dont have one anymore lol :D

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A couple of questions...

1. Why did you choose a 12V rail?

2. What made you choose that particular output chip?

3. You say in your accompanying notes that you circuit really needs a scope to assist setting it up ...is this same scope not helping you eliminate your two string fizz? (in other words, is you fizz not visible on a scope - what does you rsignal look like across the driver if you feed a sine wave into the circuit?)

Edit: By the way...your limiting method 'after' the gain controlled amp, sort of falls into the same trap that I made with my AGC circuit (when I placed it inadvertently in the wrong part of the overall chain)...the CA3080 is essentially acting as a VCA (albeit in this case a 'current controlled' amplifier using pin 5)...the signal at output of the CA3080 is rectified & then fed back into itself on pin 5. In my opinion, the sustainer circuit will work better if the signal is monitored/assessed before the CA3080 & then the gain of the CA3080 altered to suit. Else you'll need to set the whole circuit's gain to cater for the worst case scenario (thin string/high action) & ensure the limiter is set to allow that condition through - of course, this means the thicker, lower actioned strings will likely have too much gain (which could cause probs). I guess the Ross compressor designer didn't have to cater for the fact our input can grow back into a large signal (ie the Ross compressor was designed for a standard decaying guitar signal), hence their decision to limit after the CA3080. Just my opinion of course! (& anyway, you're getting good results, so we can therorize all day long - the proof is in your pudding!). As it goes this Ross compressor circuit has intrigued me sufficiently to pickup a CA3080E chip on my way home today (my first contact with a transconductance opamp!) ...I'll have a tinker with it over the weekend & see how it interfaces with my PIC's AGC output.

Anyway, once again great work (btw: it's too high a component count for me! And perhaps a bit 'high maintenance') ....is that your first sustainer build?

Thanks for the kind words. But if you have your system up and running it will be a cathedral compared to that shed of mine. :D

1. There's a highboost preamp built in my guitar that operates on 12 volts.

See the first image

R1 and 4.7uF cap are built into my guitar preamp, the MPF102 in the guitar

The 12 volts power supply I built can also be used for my guitar preamp. For that purpose I use a gutted Boss flanger with only 2 resistors and a cap inside. There is an extra resistor that grounds the cap (without the resistor that side of the cap "floats").

2. Apart from the LM386 the TDA2731A was the only one I knew! When I started thinking of building a sustainer the TDA was mentioned on the diystompbox forum to be used as headphone amp. I have actually built a headphone amp with 2 TDA2731As. Performs really well. The sound quality equals my old Pioneer amp. I only had to weaken the output signal, that was way too loud! Mind you, I use a 120 ohms - 1 ohm voltage divider. I did some tests with the headphone amp at max volume through two 8 ohms loads. Headroom (clean output power) was pretty close to what was expected. The ICs got hot but were still touchable maybe thanks to the chameleon tongue shaped heatsink. I have to say that the first time I tried my headphone amp one channel didn't work at all. After some investigation it appeared that one of the TDA7231As was dead and had to be replaced. It must have been dead when I bought it! My soldering skills can't be that bad!

I read that you are a bit disappointed in the LM386's performance, it could be you have problems with a lousy LM386, a bad apple.

I have plans to build the LM386-BS170 thingie with some modifications, see how that works out.

@ hank mcspank & zfrittz6 as well

I don't know if you're familiar with this. The sustainer device's output is inverted (180 degrees phase shift). That will improve stability, it's mentioned in the sustainiac's documentation as well.

If your grounding is not ideal (not zero ohm) there could be some output signal fed back into the input which could lead to oscillation. (The output impedance is very low, 8 ohms - in case of a non-inverting sustainers output there is a positive feedback loop).

I once thought of inserting a resistor to diminish the risk of oscillation (& fizz). For fizz it didn't make a difference and the oscillations were caused by emi (and solved with a new driver). The resistor is still in my guitar but it could be the cheapest mojo on the planet!

http://i268.photobucket.com/albums/jj18/Ma...er_earthing.jpg

3. Maybe I shouldn't have called it fizz in the first place. This is what I think is happening. When I pick the E and A string both strings want to build feedback. But you know that in the end only one string will feedback. Maybe is a bit like sumo wrestling, each of the two signals wants to push the other from the mat. It's not static fizz, there's a bit of dirt on the tone. Like when you hit your fat E-string and hold the tip of your finger close enough to the strings to touch it slightly but not close enough to dampen it.

It could be that my setup is too aggressive (much compression, 1 Watt output) and in your edit you mention something important, namely the equalization of the signal. With humbuckers the signal is too bass heavy. In the original Ross compressor there is some treble boost applied. I have removed the high boost because it introduces phase shifts that will diminish sustaining efficiency at least for the fundamental mode. I think that purely for the sustainer's functioning it would be best to slant the pickup (close to the strings on the treble side, further away on the bass side). But soundwise a slanted pickup doesn't combine well with the high boost I use. Maybe a hexaphonic pickup is the way to tackle this particular problem.

I prepared another document how to do some testing:

Steady Steed Info 3

What other sustainer devices I built?

Drivers:

magnetless see below

copper wrapped around bar magnet - flux gun - lots of EMI

hexacoil humbucker 6 rod magnets in N-S-N-S-N-S orientation - no EMI but insensitivity spots in between poles

amps:

class B powertransistor for magnetless driver - the idea: as soon as signal is being applied to the transistor half of the signal will be sent to the driver and the iron core of the driver will magnetize. No revolutionary breakthrough, no nobel prize. :D

sustainers with an overdriving preamp - not too bad for the overdriven channel but too fizzy when playing the clean channel

Old but not so gold

Cheers

Fresh Fizz

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Hi everybody,

Actually, can't count me in that list... I consider my project a failure on hold at the moment. I burned myself out from messing with that circuit and probably won't try another sustainer circuit until I learn A LOT more than I know now. I've been reading this thread on a regular basis, hoping to get up to speed, but Col and Hank are getting into some unchartered waters. With any luck, they'll have it sorted before I break down and buy a Fernandes or Sustainiac system. :D

Too bad to hear that from you. So what's the hurdle you can't take? I myself had to build 3 different drivers before I finally was satisfied with the result. The poweramp (IC) was a case of building according to instructions. That's the point were I got stuck messing around with all sorts of preamp designs. Even with a well-built driver and poweramp I got lousy sustain. Poor performance on B and E strings. Notes that strugle to build up sustain. It could be that your guitar is in the need of performance-enhancing Uber-compression like mine.

Cheers

Fresh Fizz

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Has anyone tried the sustainer on a bass yet? And isn't it possible to buy a small preamp like this, or will I have to build one?

I can wire a guitar, but apart from that I know pretty much nothing about electronics...

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one question, what would happen if i used a home made fuzz factory clone circuit instead of a F/R (or similar) circuit?

heheheheheheheh

i LIKE the way you think :D

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So my 12 parallel ebows are in construction but so far all seems to be going OK.

In the meantime, I've been working on a single EM driver to cover an octave of piano strings. My attempt is a simplified, generalized version of the "Electromagnetically Prepared Piano" (http://ccrma.stanford.edu/~sbacker/empp/).

Whereas in the original, 12 drivers are used, each with its own audio input and amplifier, I've attempted to use one larger driver, with only one amplifier.

It works alright, although it is pretty quiet, and I think too much sound comes directly from the driver. I've actually made four versions now, with varying degrees of success, each using four ceramic bar magnets, each 1.75" x 0.5" by 0.5", glued end to end, and 30 AWG magnet wire wrapped to 8 ohms.

I've also made one small driver, the width of one unison, for comparison purposes. I made this driver using a 0.5" diameter x 0.25" high circular neodymium magnet, again with 30 AWG wire wrapped to 8 ohms.

The small driver seems to be clearer and louder, and with less noticeable audio coming directly from the driver. I suppose this is due to several things:

-The circular magnet is easier to wrap wire tightly against.

-The magnetic field is more focused

-and others

Supposing I use one amplifier, what would be suggested ways of making the output as loud and clear as possible?

Just thinking aloud, would any of these be advisable?

-12 small EM drivers with circular neodymium core, each wired to 8 ohms; there are three groups of drivers, with each driver within the group wired in series; then the three groups are wired in parallel

-12 small EM drivers with circular neodymium core, each wired to 2/3 ohms, connected in series

-other solution?

Thanks!

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In the meantime, I've been working on a single EM driver to cover an octave of piano strings. My attempt is a simplified, generalized version of the "Electromagnetically Prepared Piano" (http://ccrma.stanford.edu/~sbacker/empp/).

Hmm...I had high hopes in 'porting' the principles used in the Electro Magnetically Prepared piano over to a guitar sustainer - but in my (albeit brief) experimentations...it wasn't very successful.

I reckon they're successfully doing this by chucking a fair old chunk of 'power' at each string...because they don't have to worry about EMI (on account the piano sound is 'acoustic' & not needing to use electric pickups like an electric guitar).

IMHO, you'd be better off making a single driver more akin to the many variants on here but in a scaled down version for one string. (I suggest a sewing machine plastic thread bobbin, like these http://www.brother-usa.com/usaimages/Acces...Large/sa155.jpg, winding your copper around...about 150 turns of 0.15mm wire, dip it all in molten wax then let cool to solidify the windings , find an old drill bit that fits into the hole snug, cut the drill bit to length & pop it in the hole - now place a 3mm-5mm diameter rare earth magnet on the end of the cut drill bit - voila a single string driver!)

One thing though....you shouldn't hear any sound from your driver at all - if you can, it suggest the wire windings are moving &/or the magnets....everything needs to be totally solid/rigid.

Edited by Hank McSpank

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In the meantime, I've been working on a single EM driver to cover an octave of piano strings. My attempt is a simplified, generalized version of the "Electromagnetically Prepared Piano" (http://ccrma.stanford.edu/~sbacker/empp/).

Hmm...I had high hopes in 'porting' the principles used in the Electro Magnetically Prepared piano over to a guitar sustainer - but in my (albeit brief) experimentations...it wasn't very successful.

I reckon they have the success they have, by chucking a fair old chunk of 'power' at each string...because they don't have to worry about EMI (on account the piano sound is 'acoustic' & not needing to use electric pickups like an electric guitar).

IMHO, you'd be better off making a single driver more akin to the many variants on here but in a scaled down version for one string. (I suggest a sewing machine plastic thread bobbin, like these http://www.brother-usa.com/usaimages/Acces...Large/sa155.jpg, winding your copper around...about 150 turns of 0.15mm wire, dip it all in molten wax then let cool to solidify the windings , find an old drill bit that fits into the hole snug, cut the drill bit to length & pop it in the hole - now place a 3mm-5mm diameter rare earth magnet on the end of the cut drill bit - voila a single string driver!)

One thing though....you shouldn't hear any sound from your driver at all - if you can, it suggest the wire windings are moving &/or the magnets....everything needs to be totally solid/rigid.

Thanks for the reply.

In a way, porting the electromagnetically prepared piano to the guitar would be akin to Nicolas Collins "backwards electric guitar," in which he sends audio to the guitar strings. I suppose the key would be to have enough distance between the driver and the pickups.

In the original version of the electromagnetically prepared piano, each of the 12 drivers is powered by a 7-watt amplifier. In my experiments, with both the large octave driver and the small unison driver, I've used a 15-watt amp. Basically you want to give it as much power as you can without the driver overheating. Using the headphone jack output from my Macbook with the 15-watt amp, I generally had the Macbook volume all the way up and the 15-watt amp volume about 1/2 to 2/3 of the way up.

I thought that I shouldn't be hearing any sound from the drivers themselves. This was basically the reason I ended up making four octave-long drivers -- trying to wind each one tighter. But since the last and best one still makes some audible sound, I doubt my ability to make it any better under that design. With the single unison driver, however, perhaps because it's circular and thus easier for me to wrap the wire tightly, I don't really hear any sound from the driver itself.

Also, I haven't yet potted them in wax -- I've tried some epoxies and plasti-dip, but I don't think they've done enough to solidify the windings.

I don't have a problem with making 12 individual single unison drivers. The main thing I'm trying to avoid is have each one powered by its own amplifier. Is this reasonable?

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I don't have a problem with making 12 individual single unison drivers. The main thing I'm trying to avoid is have each one powered by its own amplifier. Is this reasonable?

It's reasonable....but what's going to be key here is the coil characteristics & how you connect them all together. For example an inductance figure of 1mH (circa 150 windings) & a DC resistance of 8 ohms seems to be the ballpark for a general purpose driver ...the inductance figure is derived (in the main) from the number of windings your driver coil has.

Therefore if you want to connect say 12 drivers in series, you'd want to shoot for 1/12th of those figures per coil (therefore each individual coil should be about 0.66 ohms & 83uH!). You'd need to experiment with differing coil gauge as you'd be beating a trailblazer's path there! My gut feeling is that a coil of 83uh, that the wire would need to be very thin to be able to get 150 turns - so thin, I reckon it'd not handle the current needed to get a higher frequency type string 'excited' sufficiently.

I'd also have to assume that trying to span/excite so much string real estate with one 'virtual coil' (12 mini coils in series) would need a fairly chunky driving amplifier.

if you don't need individual control per string (as per the EMPP), then I'd go with your 12 drivers connected in parallel or a combination of series/parallel (You'd still need to be careful with your coil characteristics, but they'd be more do-able vs pure 'series' connection)

Edited by Hank McSpank

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Hello, can someone please be so kind and help me with a shopping list for the Fetzer/Ruby Amp, and and wiring diagram for a bass with 1 Pickup, Volume, Tone, and a Sustainer?

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Hello, can someone please be so kind and help me with a shopping list for the Fetzer/Ruby Amp, and and wiring diagram for a bass with 1 Pickup, Volume, Tone, and a Sustainer?

That's now how it works here - you have to read the whole thread!

I'm not sure I've ever seen a bill of materials for the Fetzer/Ruby, here's a site that comes close (I gather has simply 'pulled stuf from this thread as it credits Pete & Col )...

http://diy-fever.com/index.php?project=sustainer

re your wiring diagram...someone may have something diagrmatically to hand (I don't), but it's as simple as can be - you simply tap off your bass pickup signal either at your guitar's 1/4" jack output socket (which is simple - but not ideal as the sustainer will then be fed a 'manipulated/filtered' signal) or more preferably tap off the full unadulterated pickup signal as it appears at the input lug on your guitar's Volume pot.

Edited by Hank McSpank

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Thanks for that link, helped me a lot.

Two more questions came up recently: Will the sustainer only work if the bridge PU is a humbucker? On the Fernandes Website they say their system only works with humbuckers.

And isn't it preferable to conncet the sustainer before the Volume? Otherwise, if I turn down the Volume knob I can't use the sustainer properly.

Will it be something like this?

Bridge PU -> Volume -> Tone -> Output Jack
|
V
Switch
|
V
Preamp
|
V
Poti
|
V
Driver[/codebox]

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Firstly, your wiring signal flow chain is fine.

Re your bridge pickup query - a sustainer will work with a single coil in the bridge - after all, a guitar signal is a guitar signal (ie analogue...low level) - it's got to go into an active circuit anyway , where it can be 'treated/handled' according to the characteristics of the incoming signal ...ie single coil more gian, humbucker, less gain needed etc (my test/workshop guitar is a cheap strat copy...& its bridge single coil feeds my sustainer ciruit just fine) ...I can only imagine they recommend a humbucker, to help reduce some of the EMI spillage from their driver - can anyone else explain why they suggest a humbucker only in the bridge?

Edited by Hank McSpank

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Hey thanks a lot for your help. Now I only need to know which values should be changed for a bass in comparison to a guitar.

I'm not sure, but doesn't the driver need to be "stronger" to drive the bass strings? How can I make it "stronger"? Higher voltage from preamp? Or maybe a stronger magnet?

Anyways, will a regular humbucker magnet be fine for the driver, if I use it as the core of the coil?

And where in the circuit would I put a potentiometer to be able to change the sustain? Between preamp and driver? And which impedance should it have?

Between preamp and driver is also the right place to put a DPDT switch for an out of phase mode, right?

Edited by mock duck

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I don't have a problem with making 12 individual single unison drivers. The main thing I'm trying to avoid is have each one powered by its own amplifier. Is this reasonable?

It's reasonable....but what's going to be key here is the coil characteristics & how you connect them all together. For example an inductance figure of 1mH (circa 150 windings) & a DC resistance of 8 ohms seems to be the ballpark for a general purpose driver ...the inductance figure is derived (in the main) from the number of windings your driver coil has.

Therefore if you want to connect say 12 drivers in series, you'd want to shoot for 1/12th of those figures per coil (therefore each individual coil should be about 0.66 ohms & 83uH!). You'd need to experiment with differing coil gauge as you'd be beating a trailblazer's path there! My gut feeling is that a coil of 83uh, that the wire would need to be very thin to be able to get 150 turns - so thin, I reckon it'd not handle the current needed to get a higher frequency type string 'excited' sufficiently.

I'd also have to assume that trying to span/excite so much string real estate with one 'virtual coil' (12 mini coils in series) would need a fairly chunky driving amplifier.

if you don't need individual control per string (as per the EMPP), then I'd go with your 12 drivers connected in parallel or a combination of series/parallel (You'd still need to be careful with your coil characteristics, but they'd be more do-able vs pure 'series' connection)

Well, I tried a couple more designs. One was a thin steel core, 4" long, wired with 30 AWG to 8 Ohms, solidified with PVA glue, with a ceramic block magnet attached to the blade.

Another was like you suggested, wire wound around a plastic sewing bobbin, again potted with PVA glue, with a bolt in the middle of the bobbin and a neodymium magnet attached to the bolt.

Both worked okay, not great, although using the glue eliminated the direct sound I had been getting with my earlier attempts.

However, neither was nearly as good as the Radio Shack Miniature Audio Output Transformer, I cores removed and E cores aligned, with a neodymium magnet attached. This driver is by far the best of those that I've tried thus far.

So...thinking aloud, would it at all be reasonable to wire up 12 of these transformers in a combination of series and parallel like:

7 in series

3 in series

2 in series

and those three groups connected in parallel?

With 8 ohms per transformer, that combination seems to yield a total impedance of 8.1951 ohms. Of course, this doesn't consider inductance.

EDIT: I had incorrectly assumed that the transformers had an impedance of 8 ohms. In fact, after measuring, they have an impedance of 1.5 ohms each! So, how does that effect what I should do?

Edited by Dogue

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