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Sustainer Problems!


shiscabob

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That's pretty difficult, because so much depends on the physical layout and the cores you use.

If you take two single string coils that are each 1mH when alone and place them next to each other, the effect of mutual inductance with either increase or decrease the effective inductance of each coil (depending on if you have them in or out of phase with each other). How much they effect each other depends on proximity and, (i suppose but am not _sure_) how much of the inductance is being created by the core material.

I understand that, and I can estimate the inductance, etc. I was asking about your personal experience, if it's not a secret. Say, high strings are much harder to drive, so, seemingly, the high string coils must produce stronger magnetic field (the signal one, of course, not permanent). You can tweak it with amp gain, but you can also try to optimize the coil parameters for different strings. I have a suspicion that high string coils must be bigger, have thicker wire, while preserving about the same DC resistance. Is that correct? Once again - it's only a matter of optimization, nothing more.

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Say, high strings are much harder to drive, so, seemingly, the high string coils must produce stronger magnetic field (the signal one, of course, not permanent). You can tweak it with amp gain, but you can also try to optimize the coil parameters for different strings. I have a suspicion that high string coils must be bigger, have thicker wire, while preserving about the same DC resistance. Is that correct? Once again - it's only a matter of optimization, nothing more.

If you use thicker wire wound to the same DC resistance, that means many more turns, so a much higher inductance value - as I explained, this will act as a low pass filter, meaning that response on the higher strings will be very poor.

For driving the higher strings, you need to keep the inductance quite low!

As far as I can tell, there are a few ways of maximizing the drive that will work on the high strings.

#1 more current

#2 a more focused field

#3 choose an output cap that combined with your drivers inductance provides minimum impedance at the weakest frequency.

#1 could be provided by a class-d amp, but I've not gone there yet. #3 I have done. #2 is what I'm intending to have a go at, but don't hold you breath. RealLifeâ„¢ is very busy right now.

My idea for #2 as I have explained is to have two (or more) coils, one large one that has a high inductance and drives all strings. one small one that has lower inductance, but is only stretched over 2 or 3 strings, so its field is more focused. That's the plan, not sure it will work though, and I need to order parts before I can even think about implementing it, so I'll probably play around with variations of the design before committing to one design.

Other things that should make a difference:

Make sure that the action is as low as you and your guitar can stand - particularly at the nut.

Try different brands of strings, try heavier strings.

cheers

Col

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I have a suspicion that high string coils must be bigger, have thicker wire, while preserving about the same DC resistance. Is that correct? Once again - it's only a matter of optimization, nothing more.

I think the important thing really is that the device can change states fast enough for the frequencies at hand. So, if it is "fast" enough for the high strings and harmonics, it will surely be so for the low strings as per FF's 'solution'.

Again, experimentation is probably key to prove many assumptions. It is relatively easy to make a coil that alone will drive any string as hard as is possible, but to be able to get six of them working next to each other without adverse or quirky undesirable interactions might be more tricky.

Also of course there are other factors...I was able to get that previously shown single string driver design working very close to active pickups, even cheap single coils on a strat copy...

sustainerstrat.jpg

Bad photo I know, pre digital...also shown is the "sustainer box" and a 4 knob compressor limiter I was using for a while to test AGC ideas.

It provided me sixth something of a false hope that one might work like this, but with six of them all kinds of effects occurred even with reverse polarities, etc. They were also very sensitive to alignment, though they worked any string bending would create unusual effects. My solution was to attempt to get ever closer to the bridge till it became something like a Hex midi pickup kind of thing. For instance, this might be able to be achieved with the 'driver engine' idea, where only one driver was actually activated at a time.

I suppose I mention this because in reality, factors like EMI and 'fizz' or distortion effects are important to consider. It is not enough to just throw more power at things in general or that any driver is that localized and focused. My attempts to address these things involved a lot of elaborate shielding, my hope was that perhaps I could use metal in the bridge itself as a kind of magnetic sink or something. I guess some of this thinking was in line with the Ebow having substantial shielding around it's driver and pickup.

It might be worth studying the eBow for the way it works...close driver and pickup, extremely close to the driven string, resting on adjacent strings to avoid activating them...and the patent is one of the few if only proposed hex system for such a thing (though there are flaws in the idea), it seem s remarkably like the kind of thing you are seeking McSeem.

But the optimization thing is tricky with so many variables...I don't think there are any 'answers' without specifications of what is essentially required. So, single string drivers can not be in excess of 10mm and even at this size, generally will be touching one another. If winding to an 8 ohm resistance, depending on your circuit, that suggests to me a lot of wire, so by necessity you will need to go thinner wire I imagine...will such a driver provide enough EMF to move the strings...well, I suspect that something could be rigged up, but the thing I would and did do is to start constructing a few things with all the necessary factors in mind to see if you can create anything that does work, then tweak these things till they are optimized and after you overcome the other problems of interaction and EMI and harmonic and resonant quirks of such novel devices.

The reality is that few if anyone has done a lot of work in this area to really know, even the "theory" is only really a hypothesis till put into some practice. I believe that it is possible to some degree, though I may not fully appreciate exactly what you are trying to aim for or expecting in response, but such a system of hex pickups, individual amps, digital compensating circuitry ideas, piezo source, etc...all these things are very novel and it is hard to know what exactly is proposed and where potential major obstacles might be hiding. It is so easy to make assumptions with these things, for instance, it might be easy to assume that if you use a piezo as a source there will be no EMI problems...possibly, but I found i did and the signal needed a bit more conditioning and of course, no other magnetic coils can be anywhere near these drivers.

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I notice that these threads quickly get way off the question asked...as the original thread was too long and all in one place, that people could not find what they were looking for, perhaps this situation is even worse.

The original poster her for instance has only ever made one post on this forum, the first in this 4 page thread...and while things are interesting and all, it is effectively hijacking the thread to tack on their own projects and questions and thoughts only loosely related to it.

So, given how far this thread and the others have strayed and the criticism of the original thread...even the OP here mentions it "too lazy to read the 200+ page thread" perhaps it might be an idea for each person to start their own thread so at least it can be individually searched by subject or name.

I thought I would put this out there for discussion, as all these threads current now do seem to be taking on a bit of a life of their own. The OP's may get scared off by the amount of information not related to their own concerns and it will be impossible for people to find relevant information in the future or to reference things answered in previous threads.

At least the original thread was a one stop shop and all the information largely in one place with satellite tutorials.

So, since it has come this far and a trend if forming that has caused a lot of problems in the last year due to thread hijacking and just general confusion, I think it might make things a lot easier if people were to start their own threads on aspects that they wish to address or talk about, or particularly on their own projects. Not to put people off contributing to a question at hand, but if people are serious about their own unique projects and interests, perhaps their own thread is the way to go.

In this thread for instance, later parts are dominated by a completely different project of a similar type...till I looked, I had not completely realized that the OP was not that one...and now a lot of technical questions about a particularly specific and novel hex design which is quite a different proposal from the kinds of things that most are proposing.

So, my suggestion is that each person start their own thread for questions related to their project or interests so that all the information related to it can be collected in one place and the project and questions are more clear. The alternative is the maligned open discussion sustainer thread thing, which these things are starting to resemble, or a mash of multiple big sustainer threads that are unrelated to the OP or the question asked or any particular project and where the OP is often left far behind.

I notice that for instance, none of us answered the question about caps I don't think asked in the original post.

Anyway...I think that it might be worth discussing this before things get out of hand down the road or just impossible for anyone to utilize effectively.

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