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Humbuckers And Sustainer Driver


RM2488
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Hey

I went through the 300 page sustainer thread (not entirely!) and I think I got the gist of how it works. But I have two questions that may be pertinent to the kind of system I wanna build-

1> Why does everyone put the driver over the neck pickup and not the bridge(using neck as source)?

2> If a humbucking pickup is used, it should, in theory, be able to reject the driver (Common Mode). A small amount may get through, but the loop will, in essence, be broken, am I right? Like this:

Neck pup---> AMP

Bridge pup---> Sustainer source

Driver---> Over the neck pup.

The reason being I like the sound of my neck pup, and THAT is the one I want to use with the amp... of course, using the neck pup as the sustainer source and the driver over the bridge pup is equivalent, and humbucking is no longer a requirement (with lesser tone coloration as the bridge pup will be off!).

The main reason is that I want to make sure I can do it the way I want, before I rip out the old pickups and wind new ones. I've also considered using a piezo as the sustainer source...

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The humbucker won't reject the driver mag field completely. It perfectly rejects only fields that have no gradient, that is, namely 60Hz hum, induced by power transformers, etc. In case of the driver, there's a significant field gradient, as the driver and the pickup are placed relatively close to each other (even in case of the bridge and neck positions).

If you use a separate pickup as the sustainer source, the driver will induce the signal in the input pickup directly anyway. The only solution I can see is heavy magnetic shielding of the coils, so that, the driver mag field must be as local as possible. Probably double coil humbucker-like configuration may also help, but I'm not sure how efficient it will drive the strings.

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The humbucker won't reject the driver mag field completely. It perfectly rejects only fields that have no gradient, that is, namely 60Hz hum, induced by power transformers, etc. In case of the driver, there's a significant field gradient, as the driver and the pickup are placed relatively close to each other (even in case of the bridge and neck positions).

Ah yes, I'd thought of that. My idea is to build a humbucker like this--->Coil A - DRIVER - Coil B

So the gradient across both coils wil be more or less equal. As long as the coils match, I don't think there will be too much interference. And yes, there will be some feedback, but I'm of the opinion that it will be miniscule compared to the strings... but I'm not sure.

If you use a separate pickup as the sustainer source, the driver will induce the signal in the input pickup directly anyway.

Perhaps not, if I use a piezo...

What I really want to do, the simplest possible solution, is using the neck as source and the driver at the bridge. But it seems a lot of people avoid it, I have no idea why.

Another idea that occurred to me is to have two drivers, one at the neck and one at the bridge, and use a piezo as source. Then you can simply select which pup you want, and set the other as the driver. In fact, the piezo can be entirely eliminated, and the source and drivers can be switched (Increases chances of feedback).

I wanna know if there is something wrong with this logic, or if someone has burnt their hands this way before I get to work. Six matched coils, hand wound, is hard work! Maybe I should also think about a winding jig...

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Yes, that's interesting - to place the driver exactly between the pickups, and connect them in such a way that the driver feedback would be compensated. Needs experimentations.

My goal is different - to have a truly hexaphonic system, so that you could sustain big chords. And of course, I want to make my system totally stable and predictable. I already have a wiring nightmare with it, so, having two hexaphonic pickups would double it. :-)

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A pickup is designed to be very sensitive to electromagnetic fluctuations...it is after all designed to pick up the vibrating strings in it's magnetic field...

Now...consider the amount of electromagnetic force being put out by a driver in order to drive the strings...of course the pickup is designed to pick up little fluctuations of a vibrating string...imagine what a a great big AC powered coil is going to do anywhere near it...

You may wish to ponder how transformers work...

...

There are lots of ways besides magnetic shielding, proponents of multi coil drivers ususally are keen on them for the reverse HB effect, two driver coils of equal and opposite magnetic output, thereby neutralizing some of the effect.

However, you could shield a driver completely...the problem is that the EM output is exactly what drives the strings...so, perfect shielding would result in no effect at all! Plus, there are so many other things, the strings are metal right, and magnetic too...so the driver will put an alternating magnetic signal through them...and run along and...oh, get picked up by anything near it.

Don't mean to dampen enthusiasm though, experimentation is the key. You might want to look at others attempts though. For instance, I too had similar motivations and use the neck pickup extensively (you will notice mine are some of the few multi-pickup guitars) but the "fear" of being limited to the "sound" of your neck pickup is largely overstated in reality.

A string being driven by a sustainer is and can be quite different from that of a plucked string. You might like to consider some of the sound clips...with the tone turned down a little, you can get quite mellow flute'y effects and the sound that is produced is largely a factor of the manner that the string is vibrating, so one should not jump to conclusions about the resulting sound.

There are problems with driving the string from the bridge end as well, there are a lot of harmonic content that close to the bridge. Most of my hex designs were working towards efficiency and low power to be built into the bridge itself and to use the bridge as something of a magnetic 'sink' in the process...but alas....

Potentially, you could run a driver from the bridge and the source from the neck, but the results can be unpredictable. On the surface though, it is the same thing, same distances between the driver and source pickup, just reversed.

I'm not saying something is not possible...it was a bit of a holy grail. My motivations were largely to make installation easier, perhaps working twoards a self contained mid pickup for soemthing like a strat...no complicated bypass switching and the choice between the pickups sensing and providing the signal...you can see models like this but they have to be a lot more sophisticated than the simple designs I usually suggest.

In fact, the Hoover patent shows such a proposal for sustainic, though there is no record of it being built or sold and they surely have the means to do so...got to make up your own mind there.

Dizzy1 successfully did it, with a remarkable copy of this idea, but quite separate from my work or that thread. I have a sound clip and very convincing. It has some quirks though and a lot more sophisticated. He chose not to share the details fully. There is a post in the sustainer sounds thread on the thing.

Also, the 300+ page thread was a discussion thing that grew out of my work quite innocently. There are tutorials and other threads about that are easier to get the basics without reading any of it.

However, if planning to go down the road of experimentation, you really are going to need to be able to construct and come up with some pretty innovative solutions that others have not already tried. That's a tough call after people have been having a go after all those years. It certainly is not going to be easy or 'cheap'!

...

Neck pup---> AMP

Bridge pup---> Sustainer source

Driver---> Over the neck pup.

no...the driver and the neck pickup will act as a transformer I suspect, you will hear the driver very loudly through the amp through mutual inductance at the very least...it needs to be well away from any coils...

What I really want to do, the simplest possible solution, is using the neck as source and the driver at the bridge. But it seems a lot of people avoid it, I have no idea why.

You really need to dig deeper into how things work to understand it, it is not just a choice and these things are not done. There could be some merit as I say, but the results are not all they may appear to be for numerous reasons...this is why I stopped pursuing a lot of these ideas, amny may well be completely insurmountable.

...

Piezos...perhaps not, but my experience is that they too can squeal, they are not entirely immune as one might thing despite not being "magnetic"...even the Moog guitar has the driver well away from the bridge pickup and the piezo system. A recent review, one of the few independent I have read, seemed to indicate that the much hyped but mysterious moog thing, was not all that it pretended to be in the sustainer department. Yet to meet anyone who has seen and played the thing, so very hard to tell, no technical details, no patents...all very dodgy for now...and extremely expensive.

The Hex things, well, the jury is still out there, maybe...I spent an entire year doing nothing else...but as yet and with mine and other efforts, the results have been less than stellar and some pretty innovative stuff was tried (including the obvious magnetic shielding, ultra compact, opposing coils, piezo drivers, etc...)

...

I wanna know if there is something wrong with this logic, or if someone has burnt their hands this way before I get to work.

Yes, significant problems there, and a lot of fingers have been burnt regardless, especially mine!

Plus, till you have really heard the more conventional solutions, the assumption of what they will sound like is just that...the sustainer is an addition and quite a different sound completely...it can produce a broad range of sound and even can be tailored by going DIY if you are clever enough....

Consider this for instance, the neck pickup sounds as it does, to an extent, because it is placed away from the bridge where things are less harmonically active...so the primary frequencies heard are the fundamentals...so it sounds "smoother" and "bassier" and such. Ok...well, if you are driving the string from that location, and you are driving the fundamentals, the sound produced is largely the fundamental, and so that is the sound that the bridge pickup will produce. So, it is an assumption that the driven string will have the character of the pickup at the bridge, it far more has the sound of the "driven string" more than anything...it's definitely something to think about careful and take in mind for the amount or work that would be required to do differently and everyone pretty much has either failed at, of been unhappy with the results of.

...

You should really study how transformers work...for instance...

Ah yes, I'd thought of that. My idea is to build a humbucker like this--->Coil A - DRIVER - Coil B

So the gradient across both coils wil be more or less equal. As long as the coils match, I don't think there will be too much interference. And yes, there will be some feedback, but I'm of the opinion that it will be minuscule compared to the strings... but I'm not sure.

The driver is a completely different beast to the pickup...other than they are both coils. The can't really "match" at all. You will have a low impedance coil with a hundred or so turns and say 8 ohms...and right next to it and sharing the same magnetic field (just like a transformer) another coil of say 8,ooo ohms (to be conservative) and many, many turns of wire. This difference will amplify the perhaps 1 volt of power going through the driver, 8,000 times right there...a few slightly vibrating strings in this equation will be as nothing...and you will be putting a huge number of volts (even at a lower current) directly into your amplifier.

The device is simple in principle...the problems are not that much harder to comprehend (though there are so many) and the solutions...if there are any that are even possible...are going to be extremely difficult and frustrating to over come. On top of that, the pursuit may well be only from a perception of how the things can or do sound, not the reality...the perceived 'problems and deficiencies' far less than the assumptions that you start out with. As you get closer to a solution to these tings, you may well find that the solutions are not what you were after anyway...

You might find, as a quick and dirty suggestion and from some experience, that a driver on the bridge end of the string will do the opposite of the convention (it may well be possible to do what we do in reverse as I describe (neck as source and sound, driver away in the bridge position)...it may well drive the string with a harsh range of perhaps discordant harmonically rich and unpredictable manner, you might get it controlled enough to make a sound not unlike the character of the bridge pickup you are trying to avoid...and this sound will be going right into the neck pickup and that's what you will hear...if you are lucky and can do the work and solve the problems to make it happen. Now, maybe you could compensate with circuitry if you have those skills, certainly your drivers are going to have to be A grade...or you could run the whole thing through a modeling computer and get it to sound anyway you like...but if you are going to go that far, I'd suggest you can get all that an more with digital processing now and with guitar synths, easier, cleaner and possibly with less expense and hassle. Once you have gone as far as Hex things, all that is already available, so you may as well go all the way IMHO!

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A string being driven by a sustainer is and can be quite different from that of a plucked string. You might like to consider some of the sound clips...with the tone turned down a little, you can get quite mellow flute'y effects and the sound that is produced is largely a factor of the manner that the string is vibrating, so one should not jump to conclusions about the resulting sound.

Yes, I have heard practically every one of them... Loved the effect it has on chords. Also liked the harmonics on some... not personally something I go for, but I appreciate it nonetheless.

There are problems with driving the string from the bridge end as well, there are a lot of harmonic content that close to the bridge. Most of my hex designs were working towards efficiency and low power to be built into the bridge itself and to use the bridge as something of a magnetic 'sink' in the process...but alas....

As far as Hex pickups are concerned, the problems I foresee are either crosstalk or loss of signal on bending... but maybe someone else can do it, McSeem's project is very interesting and promising...

MY idea of a sustainer was a little different.... I don't know if it is practical enough, or how it will sound. I wanted to attach a speaker driver to the body... behind the headstock is also effective. In essence, it is like being driven by a huge amp at high decibels. But my experiments in that region led me to believe that I would also suffer from very poor battery life, and I'd hate to be tethered to a power line as well as the amp cable. A self-contained system is more appealing... just making the strings move rather than the whole body is more efficient. I also suspect I got better results 'cause I have a floating bridge... easier to excite.

Consider this for instance, the neck pickup sounds as it does, to an extent, because it is placed away from the bridge where things are less harmonically active...so the primary frequencies heard are the fundamentals...so it sounds "smoother" and "bassier" and such. Ok...well, if you are driving the string from that location, and you are driving the fundamentals, the sound produced is largely the fundamental, and so that is the sound that the bridge pickup will produce. So, it is an assumption that the driven string will have the character of the pickup at the bridge, it far more has the sound of the "driven string" more than anything...it's definitely something to think about careful and take in mind for the amount or work that would be required to do differently and everyone pretty much has either failed at, of been unhappy with the results of.

Now, THAT is new to me. Reversing the locations would actually give me the opposite effect... hadn't thought of that... :D

I wanted to stick to one pickup to avoid bypass.... I favour the neck over the bridge, a nice bluesy kind of sound. It would be simple enough to have an on-off sustainer without bypass. I record less and play live more, so I wanted a barebones system.

But it's an honour to have you take a look at this... very grateful for your insight. I think I'll go for the traditional approach for now and see how it goes from there...

McSeem, looking forward to the hex sustainer- who knows, I might get over my aversion to hex pickups and build one!

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Sustainiac has a piezo-acoustic transducer mounted to the headstock. It works pretty well, but of course, it's also mono. What is bad about the under-string mounted driver is that you can't sustain certain harmonics, namely those ones that have wave nodes right at the driver. My preliminary experiments confirm it, so, as expected. So, an ideal driver would be... mechanical, like you say - a speaker, or a piezo crystal. Just a crazy idea -- if you have a floating bridge, you theoretically can try to attach a speaker coil to it, with a speaker magnet system mounted to the body. So that, it would vibrate the bridge itself. The system is heavy, so, you probably can't sustain high frequencies.

I'm also thinking of hex electro-mechanical saddle driver, so, it would vibrate the strings in the parallel-to-the body direction, but I'm not sure if it's doable in practice at all.

As for hexaphonic in general, yes, your aversion makes sense, mostly due to the wiring nightmare. I had really hard time DIY'ing it. :-)

Besides, my system requires an audio-interface, a laptop, and a 6-channel power amp. Plus there must be some control pedals, and/or on-body pots and switches, that I could read in my software. I'm thinking of using some USB DAQ like this one: http://www.hytekautomation.com/Products/IUSBDAQ.html

But as the major benefit - you can control any parameter you want, or even assign a single pot to control ANY number of parameters simultaneously.

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Sustainiac has a piezo-acoustic transducer mounted to the headstock. It works pretty well, but of course, it's also mono. What is bad about the under-string mounted driver is that you can't sustain certain harmonics, namely those ones that have wave nodes right at the driver. My preliminary experiments confirm it, so, as expected. So, an ideal driver would be... mechanical, like you say - a speaker, or a piezo crystal. Just a crazy idea -- if you have a floating bridge, you theoretically can try to attach a speaker coil to it, with a speaker magnet system mounted to the body. So that, it would vibrate the bridge itself. The system is heavy, so, you probably can't sustain high frequencies.

Yes, the transducer idea is very simple to implement... I was not aware it is being done commercially. As far as the higher order harmonics are concerned, only SOME will be blocked, right? If I remember my physics lectures correctly, the one after the fundamental has a node at half the string length, and the one after that has it at one-thirds, and so on. So the ones with the node over the driver would probably be in dog-whistle territory. I mean, except one in the lower order. So perhaps the second order harmonic will be dead, and all other after the seventh... not a big deal, the problem is aggravated with increasing string length, and I doubt anyone would want a fifth-order harmonic on the 22nd fret. But yes, it does make it unpredictable. That's where your project is promising- you could perhaps sense it, and have an alternate driver purely for this situation.

The floting bridge has other issues- for instance, I'd be completely blocking the driver when I pitch bend with the tremolo (damping). Also, it will probably make the other strings move- forced vibration. But I'm sure that happens with the magnetic driver as well.

As for hexaphonic in general, yes, your aversion makes sense, mostly due to the wiring nightmare. I had really hard time DIY'ing it. :-)

My aversion is not due to complexity, but due to the output I desire- if there's high crosstalk, I might as well go for a blade pickup. But at the same time, I need the ability to bend strings without issues... plus I'm not going for the kind of thing you are- I like it barebones. So a traditional pickup makes sense for me. But then again, I have never used a hex pickup, so it is all speculation....

If I were to do it, I'd probably have some uC in the guitar to control it and mix all six into a single output for use with a regular amp. I'd also have a few switches for the extra "settings" and eq. or whatever. When there's a new one required, simply connect it to a computer and send it a new config-file. But hey, maybe that's just me :D

Besides, my system requires an audio-interface, a laptop, and a 6-channel power amp. Plus there must be some control pedals, and/or on-body pots and switches, that I could read in my software. I'm thinking of using some USB DAQ like this one: http://www.hytekautomation.com/Products/IUSBDAQ.html

But as the major benefit - you can control any parameter you want, or even assign a single pot to control ANY number of parameters simultaneously.

Very, very ambitious... keep us posted!

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Thnaks RM2488, I'm trying to be a fair researcher and report about my fails too, as my favorite scientist, Richard Feynman, said. One of my faults is that: I was sure it's better to mix the signal as late as possible, because, as an example, if you have a mixed record, you can never separate clearly David Gilmour's guitar from Roger Waters's voice. So, similarly, it would be great to mix the strings late as possible. But it's not so for leading solos, because of the random noise from other strings. The pre-mix in the pickup with strong distortion in the amp and its intermod has the very necessary side effect - it naturally suppresses weak signals from other strings. In hexaphonic, with a huge gain you have a lot of noise from other strings. So, I'm also trying to find a good solution for that. I have one in my mind, but not sure if it works. We will see.

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