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The circuit I had in mind was both a switch and a preamp. Essentially you'd be turning the pickup on and off buy powering or not powering the first stage transistor using a bistable circuit, other switching (Series/parrallel and the like) would be done with J-fets(probably I never got this far with it). Probably not the most effecient way ever but it seemed like a good idea at the time!

:D Pete I lost that site ages ago! I've been looking for it for months! thanks for linking to it :D

Robert

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Hello again...just looking in after moving to my island...getting a bit chilly down here! Good to see the thread continues the tradition of long threads! Still...the computer didn't survive the mov

Excellent... This will be great, and I hadn't thought about that but the 4 ohm coils would take half the time and be easier to wind....alowing the use of quick epoxy like this...hope you wore rubbe

Ok, just to prove I have been doing something lately, here's some more junk about the eBow. I'm not sure if I should be clogging up the sustainer thread with this stuff, so let me know if you guys want me to move it to a new thread.

I traced the eBow's circuit last night and did some measurements on the coils. Let's start with the circuit.

ebow_schematic.jpg

Here it is, copied directly from a real eBow. Notice anything funny? Yeah, positive feedback. I'll double check that when I get home tonight, but I'm almost positive (pun intended :D) that it's right. So, how does this thing work anyway? Most of it is pretty standard, but I haven't figured out the normal and harmonic drive modes. Flipping the switch to harmonic mode raises the DC ground by .7V on everything except the driver. Apparently it works, but I don't know how. By the way, I wouldn't count 100% on the polarity of that diode being right in my schematic... I couldn't read the marking. I also don't understand what's going on with R2. Maybe someone else can shed some light.

Anyway, here's a parts list.

U1 - definitely an LM386

R1 - definitely 1k

R2 - looked like blue/brown/orange/brown, which would be 61k, 1%. I'm not completely sure about this, though.

C1 - couldn't read it. Looks like about 47nF

C2 - couldn't read it. Looks like about 100uF

C3 - couldn't read it. Looks like about 220uF

C4 - couldn't read it. Looks like about 10uF

D1 - probably a 1n914

LED1 - blue LED. T1 package.

SW - center off mini SPDT slide switch

I know one would expect to see 10uF for C2, and 100uF for C4, but that's not what I saw.

FYI, here is another eBow schematic I found on the internet:

http://www.ece.utexas.edu/~wrobert/sus_schm_v1.jpg

This is a much more standard circuit with no harmonic mode. Probably from an earlier eBow version. The part values sort of agree with what I saw. I don't think the coil values are right, but I'll get to that later.

Here is a layout I did. It's mostly the same as the real eBow, except I moved the LED onto the board for clarity and I left out the cutouts for the coils. The connector on the top left goes to the battery and switch. The middle connector is +9V, while the other two are the two sides of the switch. There is one funny thing about the layout. Notice those big pads at the bottom? Those are in the real layout, but I don't know why. They wouldn't make much of a capacitor, and I don't see any need for test points on the board. Someone put them there on purpose, though.... ideas?

http://www.ece.utexas.edu/~wrobert/ebow_layout_all.jpg

http://www.ece.utexas.edu/~wrobert/ebow_layout_top.jpg

http://www.ece.utexas.edu/~wrobert/ebow_layout_bottom.jpg

Ok, enough about the circuit. Let's get to the coils. Contrary to what I said earlier, the pickup and driver coils are different. The pickup coil is wound with 42 AWG wire, while the driver is wound with about 36 AWG (I'm not sure exactly... but it's somewhere around 35-38). Although I wasn't able to measure them directly, my (very rough) calculations put the driver at about 20-60 ohms and the pickup around 500 ohms.

The coils are bobbinless, and they look like this:

http://www.ece.utexas.edu/~wrobert/coil-diagram.jpg

I should have wrote ferromagnetic instead of ferrite. The rings are not the same material as ferrite beads... they are probably steel. The poles are .15" in diameter, and the rings are .42" i.d. and .5" o.d. The poles, rings, and coil are all .18" tall. The magnets are .5" in diameter and .1" tall. Refer to my earlier eBow posting to see how it all fits together. This should be enough information for you to calculate your own estimate for the coil impedances. Please feel free to do so... it would be nice to have a second opinion on that.

Anyway, I guess that's about it for eBow stuff right now. All of this needs to be double and triple checked, so I'll try to get to that later.

Here are the Express files if anyone is interested:

http://www.ece.utexas.edu/~wrobert/ebow-traced.sch

http://www.ece.utexas.edu/~wrobert/ebow-traced.pcb

In sustainer news, I wound a new coil on my combined pickup/driver and I've been letting the glue dry for the last couple days. I hope to try it out either tonight or tomorrow. I used titebond moulding glue, which is all I happened to have. It's like regular PVA except thicker and dries slower. I accidentally grabbed a spool of 30 AWG and didn't notice until I was halfway done winding it. I ended up only being able to get about 6 ohms on the bobbin. It's a little sloppy, too, so I'm going to have a tough time convincing myself not to redo it even if it does work. I'm really hoping it works though... it would be very nice to finally get a working prototype after all this effort.

EDIT: Double checked the schematic and layout, and I think they're both right. I'm still not sure about the polarity of D1 and C4. I'm also not sure about the value of R2.

Edited by fookgub
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Well, I'm back again with a new driver, and this time it works. I just made a driver from two stacked magnets fro one of those magnetical knife-holders, and it does sustain. The magnet is about 5mm wide and 5 mm high, made out of some kind of soft material, and I'm using 30awg wire.

However I get a lot of feedback and squeeling when I move it to close to the neck pu. I also get a weird ticking sound, and I can actualy feel the driver vibrate when the ticking arrives. The driver also gets burning hot.

I suspect a lot of this problems are due to me hooking the driver to the speaker out of my Samick SS amp. I'm looking forward to make a smaller driver and get this stuff to work.

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Wow...interesting posts....

Thanks for that ebow stuff...I wonder if there is to be some comment of that circuit...not quite what I expected there...positive feedback on a LM386...hmmmm The circuit can get away with being this simple (no preamp) if the coils are of a suitable impedance for the input and output...perhaps the +feedback is to compensate loading some how? The thing to remember about the ebow is that it is not connected at all into the guitars circuitry, so you can get away with a lot more.

HAHA...syndromet...sounds just like on my first post...be carefull the thing could catch fire! WAY too much power there, could blow up the amp too. You have however proved the principle, problem is that you have a driver that has internal vibration...you may have burnt out the potting in the testing...much more of that heat will likely burn out the insulating enamel on the wire and short that too! Still, proven in principle and the magnets sound just right for the job...I hope that has encouraged you with the project.

This thread has always been about all things sustain and that is the first real ebow I have ever seen on the net taken apart. There have been a lot of assumptions and attempts at home building (some with success) but none I know of that are legit. I still don't quite understand why there is not some cancelling and squeeling from the device as it is used near pickups...but apparently not...hmmm

Thanks guys...now it is back to work, work for me... pete

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HAHA...syndromet...sounds just like on my first post...be carefull the thing could catch fire! WAY too much power there, could blow up the amp too. You have however proved the principle, problem is that you have a driver that has internal vibration...you may have burnt out the potting in the testing...much more of that heat will likely burn out the insulating enamel on the wire and short that too! Still, proven in principle and the magnets sound just right for the job...I hope that has encouraged you with the project.

color=#009900]pete

I opened up my driver again, and I found a couple of things that made the driver not work propperly. First of all, the magnet is 7mm wide, wich I think is a little to much. I'll be splitting it into two 3.5mm for my next try.

Second, the wire of the coil was not wound tight enought, and there was lots of air in there. Guess I have to tighten things up on my next build.

Third, the woodglue used for potting had not dried, but it had shrunk. I therefore wander if you guys can recomend me something for the potting-part. Would epoxy be good? Should the potting dry up completly?

Anyway, I guess you were right about the internal vibration. Luckily I got enough magnets for 20 more coils, and I'we ordered one of these so I guess I can afford a few more tries to get it perfect. I also have a batch of 386s' comming in, so I can build a more suiteable amp.

Edited by syndromet
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Just a little bump here. I tried out the eBow circuit on my bench yesterday, and it works as drawn. Very interesting stuff. The output is a full scale square wave when the input exceeds a certain threshold. There is no output when the input is below the threshold, which gives the circuit very good rejection of noise and low level signals. The harmonics switch varies the duty cycle of the output square wave, but does not appear to invert the phase. For now, I've just been testing with my function generator. I'll know more when I get it hooked up to my guitar.

My sustainer coil is getting better. With my modified Ruby-Fetzer, I've been able to get most of the strings to sustain. It takes some coaxing still, though. Sustaining is actually easier in harmonics mode because I can crank the gain higher before it starts to oscillate. I'll have to take a closer look at that. I've been having some problems with noise from the driver getting induced into my signal, too. I don't know if it's coming through the ground, the amplifier circuit, or if it's being induced directly into the bridge pickup from the driver. Anyway, it's progress for sure, so I'm happy about that. Eventually I'll wind another driver (hopefully my last one), but for now, I'm going to keep the one I've got and use it to test out a few different amp configurations.

I ordered a few BS170's, so I'll be able to try out the compressor that lk suggested a few pages back. When all is said and done I'll have a least three amps to compare head to head : the Ruby-Fetzer, the eBow, and the 'Aussie Compressor'. I have a feeling the Ruby isn't going to come out on top here, so this is a chance for me to actually contribute something new to the project. I'm also starting to get some ideas together about how I'm going to rebuild the eBow. I'm not going to reuse anything from the original except the casing, meaning that the final result should be a project that anyone can build without having to raid an real eBow for parts (that would sort of defeat the purpose, no?). I won't give anything away yet, but it's going to be cool. :D

Edited by fookgub
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Hi guys!

I've been thinking about building my own sustainer for a long time but haven't had the time to even think about the logistics of it. I started looking around on the net for information and i stumbled across this mighty thread...

Forgive me if these questions have been answered before, I haven't had the time to read the whole thread.

To me, the attraction of building my own sustainer is creating a polyphonic sustainer, i.e. one that will work simultaneously on multiple strings at once. Mutilation of harmonic modes, etc. will come later, but that's my overall goal.

From the information i've gathered, the most difficult part of building a sustainer is designing and fabricating an efficient string driver. Since my goal is to create a polyphonic sustainer, naturally the first thing that came to mind was using a discarded pickup as the driver.

Has anybody tried this yet? I figure if you use a humbucker and tap off each of the six pole pieces to transduce the signal from each of the strings independantly, you could then feed each signal into its own individual amplifier and feed it back to the other half of the humbucker (in the same per string fashion).

Am i oversimplifying the problem? Has anyone attempted this?

I've got lots of spare humbuckers lazing about so i might pull one apart and see how plausible this looks.

P.s. Thanks for the ebow information! I was so close to cracking my own one apart and tracing the circuit.

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I've just pulled apart a pickup, only to realise that the coil is wound around the entire pickup, making it difficult to extract a per string signal. I do however have a midi pickup which does exactly this.

It occured to me that the reason midi pickups are mounted so close to the bridge is to avoid possibility of transduction directly below a node for different harmonic excitations. Perhaps some of you are having problems with dead zones or certain notes because of where you're mounting your exciter/transducer?

I am unfamiliar with pickup mechanics so i pulled apart a single coil as well. It seems that the humbucker consists of a bar magnet underneath the two pickups, which when in contact with the humbucker pole pieces, causes them to be magnetic.

For the single coil however, the pole pieces themselves seem to be magnetic. Is this the case, or is there a hidden magnet for all of the pole pieces i am missing?

Let me know if you guys find any fundamental problems with using a pickup as an exciter. I may try to obtain another hex pickup (similar to the midi pickup, that has per string outputs) and use that as a per string exciter.

I am a little worried about cooking the thing though (they're pretty expensive) so i might try using a single coil pickup (with individually magnetised pole pieces) and wind my own windings for each of the six pole pieces. I'll try to get some signal data captures from my hex midi pickup (per string) to show you how much the string signals bleed through to adjacent pole pieces.

Let me know what you guys think :D

Edited by parsec
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Hi there guys and welcome to parsec and bobb who contacted me from Moscow via email (his english is not god!...never mind) :D

Anyway, fantastic stuff there on the ebow and the circuit, I must quiz you more fookgub on what it is doing and how it is doing it. As for the comparing of circuits, I salute you, I don't think the ruby is "best" but it should do the job...mine is a ruby like circuit but with a preamp with more gain and I'm still pretty happy with it.

Pasec...no, a driver/exciter is not a pickup. You need a coil of about 8 ohms with thick enough wire to carry the current from the amp to drive the strings. You can convert pickups though and mine is a single coil with the driver built on top of it so it will work as both a pickup and a driver. A conventional Hex pickup wont work for the same reason, but I did spend a good deal of time and energy trying to get a hex driver to work with a bit of success. There is a lot to it though and to run separate amps and all is going to take a lot of power and the magnetic signals from the drivers will interfere with eachother...also, to be truely "polyphonic" you will need a hex pickup to drive it....doh!

Actually the sustainer is polyphonic, it is just that the lowest note tends to sustain while the others decay naturally.

Oh...and fookgub,

Sustaining is actually easier in harmonics mode because I can crank the gain higher before it starts to oscillate.
I think this is a similar problem I was having till I disconected both the earth and hot ends of the unused pickup coils (relates to the relative phase of the pickup and the driver coils)...either that or the driver is still a little close to the pickup or it and/or the pickup is a little microphonic. Sometimes adjusting the pickup and the driver can fix the problem. Congrats on getting it to work a little better this time, next time for sure!

Very busy with domestic stuff and work at the moment, but always glad to see other's come on board...rest assured it is possible to make a DIY sustainer with a little perserverance and perhaps one of us experimenters will make an even better one, or even some new sustaining device altogether...best of luck... pete :D

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Actually the sustainer is polyphonic, it is just that the lowest note tends to sustain while the others decay naturally.

pete :D

The main difference i think is the fact that by creating both a hex pickup and hex driver that are independant of the guitar's electronics, you have more freedom in the electronics you can create, but more importantly isolation of the per string signals.

As far as i remember, any unstable or oscillatory system will be dominated by one frequency of oscillation, typically dictated by the transfer function/frf of the constituent components, as well as the mode shape being excited.

Generally with sustainers i think the case is because they use the guitar's output and a single magnet to drive the strings, so the system will quickly tend to oscillate at a single frequency rather than excite multiple strings at once... especially considering that a non hex driver will only be harmoniously excting one string, and be out of phase and enharmoniously exciting the others.

This is an intuitive result from traditional feedback. Even with strings tuned a fifth or octave apart, with the amp cranked, you're only going to get one string feedbacking. I suspect you would need to tune them very close to each other to get them both oscillating due to feedback.

So the goal then is to create a hex driver, which is run off a hex pickup using six independant amplifiers because this will theoretically allow each string to find its own dominant oscillatory feedback frequency, and thus be independantly excited (or so i hope).

So I've read some more of the thread, and am learning more about your (and other posters) experience with driver design.

The first question that comes to mind is, what is the purpose of having a permanent magnet in the driver? I am not very knowledgable when it comes to magnets and magnet design, but to me this seems like the equivalent of applying a DC offset to your string excitement effort (not to mention the lower permeability permanent magnets tend to have)

Have you attempted using simple steel or ferrite for the driver core? I'm wondering whether it would be possible to select a material for the hex driver cores that have a higher permeability than typical permanent magnet materials. Using such a configuration would probably make it easier to shield adjacent pole pieces from each other too, since there will be less spurious and unchanging magnetic field (assuming my DC offset assumption is correct)

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Interesting stuff parsec...

My Hex drivers eventually evolved int very compact units and could also run as rudimentary low impedance pickups. The six drivers were only 10mm long by 5 wide and 5 deep. These things were far from conventional and had numerous novel features (the specifics of which I still keep secret) some of which I have eluded to in this thread. One is the use of two high powered magnets so that the string vibrates within a neutral zone between them and an element (that avoids winding of coils) unbalances this field draging the string with it. The whole thing was set in iron powdered epoxy within an aluminium case and in some I even found room for LED's and miniture switches to activate them. The balanced field, magnetic shielding and other elements of the design allowed for the placement of the device within 20mm of connected pickups. One of the major problems though was there was crosstalk between drivers. The most critical was alignment however and string bending would have adversely effected it...in fact there is a bizarre effect that was produced (quite musical in it's own way) when the string was bent more towards one field or another (but that too is secret for now as it may give clues as to the unique design).

Anyway, I was running them from a monophonic amp but I had ideas for running it from separate amps (as you are suggesting) or a mono source with individual crossover like filters for each driver. Needless to say the things were getting extremely complicated as they were so, unable to get them as close to the bridge as I'd like (the idea being to preserve alignment and allow the use of any pickup or combination) I abandoned this work in favour of a more conventional basic coil design advocated at the moment with a few variations.

The design that I came up with was for a "very thin driver" with a coil of about 3mm thick that spans all the strings like a pickup. The wire guage is 0.2mm wound with about 200turns to approximately 8 ohms. Most of the ones I have made have used ordinary steel cores with a magnet beneath and my current one is built on top of a single coil pickup sharing the core and magnet between them. A blade design is used to allow consistant sustain with string bending. This is driven by an amplifier of about 0.5 watt with a preamp to prevent loading of the pickups. It is mounted close to the neck (or on the neck pickup on my strat) and driven by the bridge pickup. All other pickups are disconected during sustainer operation, just like in the commercial systems.

Now, although a lot of time was spent on the Hex designs (over a year) and progress was made, there are some serious logistical and practical problems with the ideas you are contemplating. However, feel free to carry on, the notion was put forward in the original ebow patent for six individual ebows permanently mounted to the guitar, not really very practical. There are enough difficulties as it is. One thing that did come of the whole Hex period was that it involved miniturization. The success of my "thin driver" design is based on the idea of a very compact driving field to create fast response (avoiding more complicated phase compensation circuitry), greater efficiency and a compact EMI field too.

So....your question...

The first question that comes to mind is, what is the purpose of having a permanent magnet in the driver? I am not very knowledgable when it comes to magnets and magnet design, but to me this seems like the equivalent of applying a DC offset to your string excitement effort (not to mention the lower permeability permanent magnets tend to have)
...and...
Have you attempted using simple steel or ferrite for the driver core? I'm wondering whether it would be possible to select a material for the hex driver cores that have a higher permeability than typical permanent magnet materials. Using such a configuration would probably make it easier to shield adjacent pole pieces from each other too, since there will be less spurious and unchanging magnetic field (assuming my DC offset assumption is correct)

Answered in no particular order...Magnetic cores are mainly used to save on space, as the driver can be made very thin, it is possible on some guitars to practically surface mount them without too much cutting into the guitar. Most of my drivers do use simple mild 3mm steel blades (from the hardware store) and ferrites are great but impossible to cut or work. I did use ferrites extensively in the Hex driver designs and in the early experimental simple single string driver experiments. Ferrite is great because of it's speed...

Now the permanent magnet has been addressed before. You don't want anything too strong, and I think you have the idea. The metal strings vibrate (as with a pickup) within a magnetic field (created by the permanent magnets) and this field is manipulated by the electromagnetic coil. It takes quite a bit too establish an electromagnetic magnetic field so a pure electromagnetic driver will struggle, while the task of manipulating an existing field (weakening or strengthing it) in which a string is already in hold is much easier. The coil is the key, not the magnet/s.

Now the concept of speed is important. By speed I mean, the ability for the driver core to change magnetic states (north and south)...it must do so at the same time and speed as the vibration of the string. This is very important as there are inbuilt difficulties already in the instrument with higher frequencies. The high strings have less mass (are thinner) and more tension and are so harder to move. The driver will have a little delay as it is in that to establish a change of states it must first loose all of it's previous state and move in the other direction. What you don't want is a delay (phase difference) so that by the time the driver has changed states, the string is in fact moving back so that the string is being pulled when it should be pushed. So, speed is very important so that the driver/s remain in sync with the strings enough to create the effect.

Hope this helps and is of interest to readers of the thread. I think there are things to conquor even more urgent that true polyphonic sustain. I'd love to see a sustainer that could be used with minimal modification to a guitar and the use of any pickup for instance. But for now, I am content with my "sustainer-strat" and that it does what it does, even with a few quirks along the way. The harmonic function, regardless of the sustain effect is pretty neat and it does open up a range of unique effects as well as controlled feedback...

best of luck with the experimenting... pete :D

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I have a question and I am pretty sure has already been addressed before. I am building a guitar that will have a hexaphonic tune-o-matic bridge as the only pickup system on the guitar. Will the summed piezo signal work as an input for the driver on a sustainer? I realize I will need a driver coil and power amp but will this function correctly with a piezo input?

The idea is to have a simple single coil driver in the neck and that's it for 'pickups'. The guitar's sole function is a synth driver.

Thanks to all for this amazing thread!

~David

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I have a question and I am pretty sure has already been addressed before. I am building a guitar that will have a hexaphonic tune-o-matic bridge as the only pickup system on the guitar. Will the summed piezo signal work as an input for the driver on a sustainer? I realize I will need a driver coil and power amp but will this function correctly with a piezo input?

The idea is to have a simple single coil driver in the neck and that's it for 'pickups'. The guitar's sole function is a synth driver.

Thanks to all for this amazing thread!

~David

David,

the short answer is yes.

The longer answer is that you'll need to think about how you're going to hook it up. Do you have a buffered output available, or are you going to connect the piezos in parallel with the midi converter? In the first case, you're pretty well set. In the second case, you need to increase the input impedance of the sustainer amp (I'm assuming you're planning to use the Ruby-Fetzer circuit here).

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Myka...great to have you try this out...

Will the summed piezo signal work as an input for the driver on a sustainer?

As fookgub says...YES!

In fact such a guitar would overcome one of the main difficulties discussed, that being EMI between the electromagnetic driver and traditional electromagnetic pickups. Piezos present no such problems as they are not magnetic.

On a side note...My current thinking is that the sensitivity (gain control) on the sustainer circuit is not really required (a trim pot perhaps) but will require a switch for on/off and for harmonic function. Your proposal also has the advantage there as you will not have to bypass magnetic pickups, simply turn the thing on and off. I don't see that there should be a problem using the fetzer/ruby circuit with the piezo system as the piezo's themselves are probably buffered/preamped (are they not?), with their own circuitry.

Be aware that a single driver sustainer like this or any other (unless the proposed hex driver, hex amped, hex pickup type design) is polyphonic but the sustain tends to be on the lowest sounded note. For single note lines this is no problem, but for chord work it is typically the root of the chord. The other notes decay as usual. This can actually lead to some neat effects such as infinite drones and tapped bowed like bass lines or in harmonic mode, bass notes that morph into notes above the chord.

The only real problem I experience with my sustainer strat is the click when turning the device off. Universally, it has been suggested that this is in part an interaction with the magnetic pickups. Otherwise, the device works well and has given me no problems at all for well over a year with pretty much daily use.

Also, it does use a bit of power, so you will most likely want a separate battery to run the sustainer I would think, and another for the piezo system...or possibly some kind of remote power.

So, just to be sure...the proposed receipe for the driver is 0.2mm wire of about 200 turns (to about 7-8 ohms) around a steel core/blade with a magnet attached under it (I used 3mm ordinary steel) or a magnet as the core, and be sure to pot it completely to avoid vibration within the windings. The ideas presented here are based on a thin driver (mine is 3mm deep) which condenses the energy and seems to allow it to work fast enough to avoid further complicated circuitry.

The driver acts like a speaker coil and the strings are analogeous to the speaker cone, vibrating in sympathy with the amps output and creating a feedback loop that will sustain the strings infinitely.

Sounds like a great project, keep us posted... pete :D

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Thanks for the replies. They are very encouraging!

Do you have a buffered output available, or are you going to connect the piezos in parallel with the midi converter? In the first case, you're pretty well set. In the second case, you need to increase the input impedance of the sustainer amp (I'm assuming you're planning to use the Ruby-Fetzer circuit here).

The piezo system is from Graphtech and has a separate buffered output for the piezo signal (that is separate from the hexaphonic output). I planned to use the Ruby circuit. Will this work for what I need?

piezo-ruby.jpg

Also, it does use a bit of power, so you will most likely want a separate battery to run the sustainer I would think, and another for the piezo system...or possibly some kind of remote power.

The Graphtech preamp runs off phantom power from the synth device when plugged into it (a Roland VG-88 in this case). I plan to tap into this to drive the circuit. I am pretty sure the preamp outputs 9-volts for auxillary power (if not I may have questions about how to step it down).

So, just to be sure...the proposed receipe for the driver is 0.2mm wire of about 200 turns (to about 7-8 ohms) around a steel core/blade with a magnet attached under it (I used 3mm ordinary steel) or a magnet as the core, and be sure to pot it completely to avoid vibration within the windings. The ideas presented here are based on a thin driver (mine is 3mm deep) which condenses the energy and seems to allow it to work fast enough to avoid further complicated circuitry.

Cool! This was my next question and you answered everything I had thought to ask. Thanks!

I will definitely keep all of you posted on this as I make progress. I plan to start experimenting in 1-2 weeks.

~David

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BTW, I ordered the wire for my pickups/ driver last night, and I will be hopefully spending a bit of time in the next few weeks on the sustainer circuit and driver. Progress wont be too rapid though, as this will just be a sort of side project to keep me sane in whatever free time I have during my exam period.

I look forward to seeing the progress of your sustainer David! Its great that you are trying new things; a piezo pickup and remote power.

The word 'hexaphonic' that I keep reading in your posts keeps making me think how cool it would be if you could make a hexaphonic driver! That would be quite ambitious though, because you'd surely need 6 individual amps and 6 drivers, one for each string...

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The piezo system is from Graphtech and has a separate buffered output for the piezo signal (that is separate from the hexaphonic output). I planned to use the Ruby circuit. Will this work for what I need?

I see no problem with the circuit you've drawn.

The Graphtech preamp runs off phantom power from the synth device when plugged into it (a Roland VG-88 in this case). I plan to tap into this to drive the circuit. I am pretty sure the preamp outputs 9-volts for auxillary power (if not I may have questions about how to step it down).

The Graphtech system's auxiliary power output should be the same as your power supply voltage. This is based on what I know of the Ghost system. It may be different when you have the midi converter involved, but I doubt it. The good news is that the 386 will run from a variety of power supply voltages. I wouldn't go much below 8V, but you can easily go up to 12V. Some 386 varieties will run up to 18V, but you need to check the datasheet to make sure you have the right part.

Anyway, I can't wait to see the finished product... I'm sure it will be excellent.

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Wow...this sounds great Myka. Phantom power will allow the device to be on the whole time and allow for turning off simply by turning down that sensitivity control to zero if you wish. A DPDT push/pull on the pot would allow for the harmonic function too if you want to keep it simple and clean...just one control. With the extra power of 12 volts, and phantom power at that, that basic circuit should work fine I'd say though you may wish to put in a 10uF cap between pins 1 and 8 in addition to that trim pot (this will help to control any internal oscillations). I'll be facinated to see what you come up with for the bobbin material...what about a bit of timber veneer. As for potting, I used PVA (wood glue) but other's have suggested epoxy (which Tim used successfully). It is very important as the coil will try to vibrate and this will produce an unwanted signal and cause a lot of inefficiency. I suggest potting as you go so that the glue completely fills between the windings, gently pushing the windings down on the sides (where it is looser) with a stick, then tightly wrapping it with electricians PVC tape. This is the method I used and the coil will end up (on a 3mm blade) about 3mm thick and about 10mm wide (thinner than a typical single coil). By winding a few turns, then applying glue, the further windings will squeeze out any excess and you can always add more. Can't wait to see how it all turns out... pete :D

Oh...and good luck to everyone else out there. Ansil's ideas are a little different, but give it a go if you dare, it's not quite the same device as we are describing here, so perhaps don't expect it to do the same thing. Special thanks to fookgub for your well informed comments, unfortunately I am very busy lately but keep looking in from time to time...cheers p

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I wanted to share the results of my first experiment:

Yesterday, I took an old single coil I had lying around, removed the coil and put a couple dozen windings to get roughly 10 ohms of 0.2mm wire on it. Unfortunately, I forgot to add glue while winding it, so I ended up with what is a very inefficient loudspeaker - when I put in a signal, the coil itself creates more sound than the strings it is supposed to drive :D

Well, I still have some wire left, I guess I'll just do it again. Or I should search if I still have some leftover wax that I used to pot a few pickups several years ago...

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welcome stewreo to sustainer land!

Nice try...the potting is very important. I also suggest that the pickup bobbin should be "blocked up" at the bottom leaving only 3-4 mm on the top portion to wind the driver on to...this is the thin driver principle of mine. This condensed coil with many overlapping wires helps with efficiency, very important with the high strings. I wouldn't have thought a couple of dozen turns would give you 10 ohms...more like 100-200, but it still is not that much really. Might want to check that multimeter and wind between 6-8 ohms.

Here is a picture of my singlecoil driver again...

pup-driver1a.jpg

the little thin blue bit at the top is the driver...the black bit is the single coil windings.

If you didn't pot it, it really shouldn't be too hard to wind it back off onto something and re-use it...still, wire is cheap when you find a place that sells it. Also, what are you using to drive the thing...beware of anything too powerful...

best of luck with no#2... pete :D

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Just to help out all of you playing with the lm386 chip heres some info, actually the question above about resistor r2 [didn't see anyone answer it so i thought i would send ya a link]

http://www.national.com/an/AN/AN-263.pdf

http://www.national.com/an/AN/AN-512.pdf

http://www.national.com/ds/LM/LM386.pdf

third link page 5

theres also a section about using positive feedback in the lm380 app notes to get increased gain.

hope that helps.

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I also suggest that the pickup bobbin should be "blocked up" at the bottom leaving only 3-4 mm on the top portion to wind the driver on to...this is the thin driver principle of mine. This condensed coil with many overlapping wires helps with efficiency, very important with the high strings.

This might be my main problem here - I did a #2 where I "potted" the coil by adding hot glue while winding it, and it still doesn't pull strong enough on the string. The coil is spread over the entire height of the pickup, so I guess I should insert some blocking and wind #3 soon.

I wouldn't have thought a couple of dozen turns would give you 10 ohms...more like 100-200, but it still is not that much really. Might want to check that multimeter and wind between 6-8 ohms.

I'm pretty sure the resistance is accurate. Also, depends on how much you define as "a couple of" - I never counted, but I was most likely in the >100 range. Also, the DC resistance of a coil is less than its AC resistance, if you measure the resistance of a 8 Ohm loudspeaker with a multimeter it'll show something around 6 Ohms.

Here is a picture of my singlecoil driver again...

the little thin blue bit at the top is the driver...the black bit is the single coil windings.

Thanks, I'll try to follow that. I should build myself a winding machine again, so I can add another coil to get a passive pickup as well.

Also, what are you using to drive the thing...beware of anything too powerful...

I tried different things - the headphone output from my portable MD, the amp from my computer speakers and I even tried the output from my stereo amp.

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  • 2 weeks later...

OK, I have all the parts and supplies ready for my first sustainer driver and poweramp (rememeber this one will have a buffered piezo signal). Thanks to everyone for this thread becuase I don't really have any questions about how to proceed (this in an of itself is a wonderful thing!).

What I do have is an idea that I wanted to get some feedback on. Has anyone built a driver with adjustable pole pieces? Could this help deal with the higher strings?

~David

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What I do have is an idea that I wanted to get some feedback on. Has anyone built a driver with adjustable pole pieces? Could this help deal with the higher strings?

~David

David,

I'm not sure what to say here. On the one hand, it seems like an elegant way to mitigate at least some of the string balance issues. It would require a slightly different magnet structure than the current design, but I doubt that would pose much of a problem for you. On the other hand, I feel that the blade polepice may be more effective in directing magnetic flux toward the strings. I have no evidence to back this up, though... I guess you'll just have to experiment.

(holds breath and waits for Pete to announce he's already tried it...)

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