Sustainer Questions

[al s.]

Hi... a few questions about sustainer drivers....

Surely, some people out there have already tried these ideas and the answers are known.

My questions are about using cylindrical pole pieces for the driver......(as opposed to rails)

#1 Is there a problem with bending strings?

#2 can you vary the the pole height to even out the string response to the driver?

#3 would rare earth magnets be effecitive as the pole cylinders?

#4 per the fernandes patent... an air gap between the magnet and the pole piece has an effect.

anybody tried it?

Thanks. Al S

[Akula]

1. Not that I've noticed.

2. You can, yes, but theres only so much this'll help with sustaining the high E and B strings. Really you need an efficient driver, and a good circuit to provide enough power to vibrate these strings, but naturally you'd want to back off the lower strings pole heights so they dont become overwhelming.

3. To my understanding, these neo-magnets are too strong, and they pull the magnetic field around too tightly, so theres isnt enough range to reach the strings.

4. Nope, never tried it. Could be an interesting idea, not sure how it'd help though...

These are all my personal thoughts and experiences. No doubt I'm wrong on a few of these, but I thought I'd offer my help anyways

[Tim37]

#3 would rare earth magnets be effecitive as the pole cylinders?

a sustainer driver is nothing more than a electro magnet you need iron pole peices to make it work.

thats about all the help i can give you.

[col]

#3 would rare earth magnets be effecitive as the pole cylinders?

a sustainer driver is nothing more than a electro magnet you need iron pole peices to make it work.

thats about all the help i can give you.

That is nonsense !

A sustainer can only work if there is a reasonably strong permanent magnetic field (try it without if you don't believe me).

Also, you don't actually need iron or steel core at all - just a permanent magnet and a coil. However, a coil with a good core can have more power with the same number of turns - or the same power with fewer turns.

Some reasons why a permanent magnet is needed:

reason #1

The field developed by the electromagnet is weak, so it can't generate enough power to align enough of the the magnetic domains in the steel of the strings.

The permanent magnetic field aligns far more of the magnetic domains in the strings so the strings become far more sensitive to the pull of the tiny electro-magnet

reason #2

Without permanent magnetic field that is much stronger then the electromagnet, the alternating current in the driver coil would cause the magnetic field to have its polarity reversed every cycle. This would mean breaking down and re-forming the domains in the string and also destroying and reforming the drivers magnetic field - both things take mucho energy and time.

Having a permanent magnetic field means that all the sustainer does is alternate between a bit more pull than the permanent magnet alone, and a bit less pull than the permanent magnet alone. No destroying and reforming of magnetic domains or fields is required

One of the tricky parts of designing a sustainer driver is getting the permanent magnet just right. To weak, and not enough of the domains in the strings will be aligned, too strong and there will be too much pull on the strings affecting tone - above a certain point, where most of the domains are already aligned, adding more permanent magnet force will not help, only hinder.

@ al S, I can't see any reason why rare earth magnets wouldn't work. As long as the field at the strings is not too strong or too weak and the domains are aligned in the correct orientation.

cheers

Col

[psw]

Hi... a few questions about sustainer drivers....

Surely, some people out there have already tried these ideas and the answers are known.

My questions are about using cylindrical pole pieces for the driver......(as opposed to rails)

#1 Is there a problem with bending strings?

#2 can you vary the the pole height to even out the string response to the driver?

#3 would rare earth magnets be effecitive as the pole cylinders?

#4 per the fernandes patent... an air gap between the magnet and the pole piece has an effect.

anybody tried it?

Thanks. Al S

#1 No...separate pole pieces work fairly well...if very compact a driver there is only going to be so much 'core' and a fair amount of air that might effect things with performance.

There is little problem with SC drivers anyway with single poles, the effective magnetic field is kind of combined anyway...the magnetic field is not independent...so there is little problem with bending string in mine anyway.

#2 I did some like this with bolts as poles, but it didn't seem to make that much of a difference compared to other strategies (like giving the circuit a bit more of a treble bias for instance). It isn't as big a "problem" as people might think...similar with pickups, it doesn't alter things that much compared to the qualities of the overall qualities of the device.

#3 I used rare earth magnets extensively, they can work, all my hex drivers had many rare earth magnetis in it...but my experience is NO. These things are powerful and the field very compact (the pole on top is heavily attracted to that below) and can seriously effect the strings vibration adversely (very easy to get "strat-itis". An equivalent strength for a single alnico fender sided pole in neodymium gets you a magnet of about a 3mmx3mm disc...so seriously small, but all the energy is very different.

So...my opinion is that with conventional use, rare earth is not a good option...a few people besides me have tried them without a lot of success. I did stick a row of neo-discs to a 3mm blade at one point (to make compact) but a bar of ceramic on the same coil seemed to work a bit better. There are pics of things by me and tim from memory that show these kinds of things...

That is not to say they can't be used in some innovative ways. Perhaps between dual blades and of course I made arrays of them to counteract pull in the Hex designs...the so called "balanced field"...again material in the original thread.

#4 Not sure what you are are looking at there. An air gap between the core and magnets has been used in pickups ("air" pickups) but I don't know that this is an advantageous strategy.

But your experience or specific use may vary. Mainly with strong neodymium magnets, I have had problems with this very compact field...even connected to a core or poles (like bolts or whatever) there is a very strong attraction to the opposite pole which is typically very close and so the field has less influence on the strings themselves. If too close, they pull on the things...if used alone, there is very little but air in the coil that affects inductance and so effectiveness.

They use them in the pickups by the "animal magnetism guy"...forget their name...but these use a lot of adjustable poles and sideways neo.mags and such. They are not a 'miracle' pickup really. Although there is some use of neo-mags in pickups, they are not that great except in special applications (field shaping in SCn and fender noiseless for instance). However, despite they having a space and cost saving, these things have not proved to be a great choice in conventional designs and I think there are reasons for this.

Col is right that you can use the magnet in the core, I have, but I have found there is a lack of choice or machining ability with these things. Some have cut down alnico fender poles for instance. Tim was able to machine a ceramic. For some reason, I have found that internal magnet cores are not as good as similar things with external magnets. It does not need to be a very strong field. My tele's is not that strong but I suspect it does benefit from being quite close to the neck pickups magnetic field at that portion of the string.

Getting the magnetic strength right, I use a conventional pickups kind of strength as a guide. I suspect that with some dual coil designs, such as a rail or HB format, you could use a bit more strength. On single coils, it is very susceptible to strong fields...so it is very important to go too far here. With neo's it is so easy to misjudge this strength and to get effects from teh sheer compactness of the magnetic field. These kind of things were observed in real life experiemnts and in modeling with FEMM. I think some of these FEMM models may be posted using neo's and other types of magnetic material.

[col]

For some reason, I have found that internal magnet cores are not as good as similar things with external magnets.

Here's your reason:

If you have 8ohms of 0.2mm wire wound around a steel or iron core, the inductance will be considreably more than the same 8ohm of 0.2mm wire wound around a ceramic magnet - about 60% more in my experience with the steel I use for cores, YMMV.

Using 60% as a example, that means that if your steel cored driver had 120 turns of 0.2mm, your magnet cored one would need about 150 turns to have the same inductance (instead of 0.2mm you would probably use 0.23 to get a similar DC resistance).

A few calculations show that the magnetic pull of the *same* coil without a steel core will in this case be 20% less that with the core. The extra 30 turns fixes the disparity.

The reality may be a little bit away from this ( a few turns one way or the other depending on the non linearity of the core material, and the quality of the winding), it also depends on the dimensions the core and the type of metal - so the only really sure way is to measure the inductance, then wind to match it with a thicker gauge of wire.

cheers

Col

[McSeem]

The problem is not only with local and strong permanent field. The core of the coil must be made of some soft magnetic alloy with high permeability, as high as possible. Ideally, it must be some alloy used for magnetic shielding. I'm trying to experiment with pins from a humbucker, doing some lathe works with a cheap drill in a vise, connected in series to a 300W lamp with a dimmer to adjust speed.

Then you attach small disk magnets to the bottom in order to have magnetic bias. Still waiting for parts from Graphtech; I spend more than $500 to order 6 acoustiphonic preamps plus pickups and stuff. Then I'm going to use a low latency multichannel audio interface and process everything in software, for all 6 channels in parallel. So that, I can take a hexaphonic signal, mix and pan it as I want to stereo outputs, plus use another 6 outputs for the sustainer driver. The point is I can easily filter and distort the signal, adjusting the parameters for each string independently. Plus, it's easy to implement frequency independent phase shift, add some "burst" mode to enforce sustain quicker, and so on ...endlesss possibilities.

The point of using piezo pickups is that there's no direct EM feedback with the driver, so that, the sustainer can be "portable", you can put it on your right little finger and move along the strings, starting different harmonics.

[col]

The problem is not only with local and strong permanent field. The core of the coil must be made of some soft magnetic alloy with high permeability, as high as possible. Ideally, it must be some alloy used for magnetic shielding.

why?

Plus, it's easy to implement frequency independent phase shift...

I can see some point in this, however it is not possible to 'correct' the physical phase difference between driver and pickup - the only way to preserver the true vibration of a guitar string is to have the pickup and driver in the same place (eg. optical pickup / magnetic driver).

The reason for this is that when a string is picked, two 'kinks' move lengthwise in opposite directions on the string - 'correcting' the phase difference for one kink will increase the phase difference of the other.

With a well designed circuit/driver system, any other phase distortion should be low enough to be acceptable.

(It is true that - as mr McSpank has stated - a guitar sound morphs into something like a sine wave. However, the initial part of the sound, which is what gives the sound it's character, will be altered by a 'standard' sustainer...

even with the driver and pickup in the same place, there will be problems. A guitar string vibrates in 2D (up/down and left/right), the sustainer has to overcome this natural vibration and force an up/down 1D movement. This effect is also likely to have an impact on the sound of the note's 'attack')

The point of using piezo pickups is that there's no direct EM feedback with the driver, so that, the sustainer can be "portable", you can put it on your right little finger and move along the strings, starting different harmonics.

Piezo is an ideal way of reducing/removing some of the unwanted noise that might be introduced by a magnetic pickup/driver based system.

Unfortunately, a piezo pickup ain't going to give you a truely authentic vintage wailing guitar sound. (even with fancy digital modelling IMO).

I'm not so sure about the value of a finger mounted driver. A sustainer is VERY sensitive to the distance between driver and string (the pull of the magnet is inversely proportional to the square of the distance). That's why the ebow has a setup whereby the strings either side of the sustained one are used to position and guide the driver.

cheers

Col

[Tim37]

humm well i guess im wrong then. sorry.

[McSeem]

The problem is not only with local and strong permanent field. The core of the coil must be made of some soft magnetic alloy with high permeability, as high as possible. Ideally, it must be some alloy used for magnetic shielding.

why?

Because of magnetic permeability. Say, neodymium magnets have low permeability, but high coercivity. In other words, if you compare the inductance of the same coil, wound on a neodymium magnet and a piece of nail of the same size, there will be a huge difference.

I can see some point in this, however it is not possible to 'correct' the physical phase difference between driver and pickup - the only way to preserver the true vibration of a guitar string is to have the pickup and driver in the same place (eg. optical pickup / magnetic driver).

The reason for this is that when a string is picked, two 'kinks' move lengthwise in opposite directions on the string - 'correcting' the phase difference for one kink will increase the phase difference of the other.

With a well designed circuit/driver system, any other phase distortion should be low enough to be acceptable.

Of course, I agree, the input and the driver must be as close as possible, but still it's interesting to experiment. With a mounted driver, I know the distance between the bridge pickups and the driver, I can compute the phases for each harmonic accurately (and yes, for each string and each fret), I can use FFT to adjust the phases in conformance with the string vibration at a particular position. The overall latency can also be accurately calculated and/or adjusted. So, it may sound crazy, but I can tweak the signal very flexibly with DSP, which you can never achieve with analog circuits. Finger mounted driver won't work properly in this case, but still can be potentially used for fancy/strange effects.

Piezo is an ideal way of reducing/removing some of the unwanted noise that might be introduced by a magnetic pickup/driver based system.

Unfortunately, a piezo pickup ain't going to give you a truely authentic vintage wailing guitar sound. (even with fancy digital modelling IMO).

Right, it's going to be more like acoustic sound, at least, with Graphtech pickups. However, I also have a hexaphonic mag pickup at the bridge, which can also be used.

I'm not so sure about the value of a finger mounted driver. A sustainer is VERY sensitive to the distance between driver and string (the pull of the magnet is inversely proportional to the square of the distance). That's why the ebow has a setup whereby the strings either side of the sustained one are used to position and guide the driver.

I'm not sure either, we will see. If the strings can be drivable at about 5mm, it can be used. At least, in my early experiments with a very weak driver (250 ohms coil) and a bridge single coil pickup, I could start 2nd, 3rd, up to 5th harmonic by just moving the coil along the string.

BTW, for a true 2D sustainer you would need stereo pickups and drivers placed like this:

 

 string

	*

  /   \

drivers

McSeem

[psw]

Interesting col

I didn't just try ceramic, neodymium didn't work out to well, don't recall if i tryied alnico

I did have remarkable success with the newer wafer coils sitting on the top edge of alnico and similar strat pickups...these are only 1mm thick...so there is not much coil around a core itself...but you seem to have that prognosis correct with what I experienced perhaps

Induction unfortunately is still not a possible measurement with my tools. I have followed a thread on inductance meters and they are to costly for me to justify and the reported errors in the cheaper models seem substantial...so, alas, measuring actual inductance may be difficult for me.

I am a bit fuzzy with the flu this early morning, but is it high permeability that you want. Retention of the magnetic field as the drivers coil goes through it's AC cycle is cited to be a cause of lag, lower efficiency of the device through phase difference.

There are a lot of potential problems with the whole Hex driver scenario. One that I encountered quite a bit was separation of the magnetic and driver elements of the device. Regardless of strategies I employed, the driver elements did interact and often in peculiar ways depending on the kinds of strategies employed.

For instance, that "2D thing" is very close to the kind of thing I extensively used with the "balanced field" idea. The driver elements still interacted with one another.

That whole "system" is pretty extensive, and good luck with it, but I am not sure what it is actually trying to achieve.

My perspective has always been that there is no "ultimate" sustainer. I really am not persopnally that fussed that the sustainer sounds different from a conventionally plucked string...in a lot of ways that is the point. I think, and especially when you start getting into the whole DSP thing, that you may as well use digital sample and hold technology to sustain a sound. I have heard some of Roland's high end guitar synth and processing units demoed with fenders V guitar that does exactly that...it even has light beam control interfaces...so you can sustain a note potentially or manipulate it various ways (pitch, modulation, etc) with the wave of a hand, or indeed the headstock! Plus, you can even have that play while you play something else...so combining looping and sustaining kinds of things. It sounds exactly like the guitar of course, for that's what it is a high end digital sample of what is being played.

For the more organic things that general DIY'ers are able to contemplate and complete, this kind of thing is perhaps beyond reasonable possibilities.

I know that I fell deeply into the 'trap' with the hex drivers that I made elusively for over a year, because I anticipated a lot of problems or solutions to perceived problems before I had gotten beyond the more basic things other than successfully running a single string from a miniture driver (about page 2 of the massive thread). I then extrapolated that I would need just 6 of these to get real polyphonic response and other such boons for the thing. They quickly developed in complexity as such basic coils will interact in so many ways, many that were not anticipated.

We all know and accept (I hope) that a driver will induce a signal in a nearby coil like a pickup next to it in much the same way a transformer works. Now, why would it not be the same with driver coils all right up next to each other with a maximum gap of perhaps 10mm between strings? This is I believe the crux of the problem with Hex drivers. Not that I am not saying that there may be benefits from such a pursuit, but are those benefits worth it and such basic problems physically surmountable.

...

For the more down to earth approaches that the OP al.s asks. As always there seem to be a lot left out of the questions. What is the intention of such a design. Is the use of neo-mags to make things more compact or because they are cheap and easily obtainable, or that the tag "rare earth" has some exotic appeal... The end result of the magnets is to create a magnetic field of a suitable quality that works.

Last time I tried it was on the first test for a compact driver on my tele...similar to what's on it but with a core of 3mm rare earth discs...way too strong an attraction to the strings.

The time before that was on a bass guitar...using the old hex driver ideas, I made 4 drivers mounted at the bridge with 8 very strong neomags to either side of the strings...interesting but I did not pursue it to far, in part at least because of my sudden move (a process I am in the middle of this week in fact). These hex things though are not like conventional drivers, a simple coil around a magnet...I honestly ran out of ways I could ever get them to be truly separated. Maybe you will have more luck and innovation in that regard.

The finger mounted thing reminds me a lot of the nano-ebow thing I made (mentioned in the thread a few times)...taking the ultra-miniture hex drivers and using another to use as a 'pickup'...you can get these things very tiny...unfortunately the circuit was as big as you might expect...not finger sized. So, I had this idea of doing much the same, taking a line out from the pickup and a sustainer amp circuit...really going back to the original single string driver tests from the start and the hex things. But then are you going to really want a wire going to the driver. I think that mic stand mounted device is a better way of creating something like this perhaps and a bit more practical in performance.

...

Otherwise, I don't mind that the typical sustainer drives the string differently from "natural vibration"...as col says, a lot of that stuff in the attack is the character of a guitar note...if you are going to hold that note long after that initial attack, then do you really want a it to lack the character. I mean, these things ultimately should sound musical and musically useful. That a violin bow sounds differnt from a plucked string on the same instrument has never been an issue, why should one think or aspire to such things with these magnetic ways of exciting a string. And, while the violin bow can hold a note indefinitely, the bow can provide so many other ways of controlling expressively a note of any duration. Similar things are possible with such devices as a "sustainer"...unless you aspire with great effort and technology to avoid the character that can be introduced to such an activated string in the pursuit of what is deemed "true".

I ahve done some stuff with acoustics and piezos...not that keen on the sound or the musical usefulness. The old Variax thing has always been muted as having potential with this kind of thing...for the absence of magnetic pickups and for those so far into modeling. But again, for the organic qualities that a typcial sustainer can offer over the digital sample and loop things that are so much easier and actually does produce the sounds some apparently aspire to. Adding any other magnetic pickups to such a guitar in addition can cause problems could interfere with or prohibit their use.

These proposals always sound so familiar, but while put forward for a few years now, nothing seems to have come of them at all except simple devices, even when those intentions were explicitly stated. But, good luck, perhaps you will have something of a first behind the mysterious Moog guitar and show how it can be a musically useful device, not just a technical accomplishment.

[col]

The problem is not only with local and strong permanent field. The core of the coil must be made of some soft magnetic alloy with high permeability, as high as possible. Ideally, it must be some alloy used for magnetic shielding.

why?

Because of magnetic permeability. Say, neodymium magnets have low permeability, but high coercivity. In other words, if you compare the inductance of the same coil, wound on a neodymium magnet and a piece of nail of the same size, there will be a huge difference.

Yes, however once you get above one or two mH inductance, you start to kill the high frequency response, and the driver can't drive the higher string/fret combos. (impedance due to inductive reactance rises with the inductance)

inductances that are too high to be usable are possible without high permiability cores.

(It is possible (I think - still to try), to use a combination of two or more coils with different properties combined with some passive impedance balancing LCR networks, to get some success with slightly higher inductances, but they are still well within the realm of what is possible with an air core.

I am looking at a 6 string 6mH coil combined with a 3 string 1.2mH coil. The impedance is nearly the same from 82Hz through to 1200Hz with acceptable phase distortion throughout that range.

The idea is that the 6mH coil will get more current at low frequencies while the 1.2mH coil gets more (~65%) of the current at higher frequencies.

The 6mH coil has more magnetic pull, but it's response falls off rapidly after about 300Hz. The 1.2 mH coil is tweaked to provide good drive from 300Hz to 1200Hz, and due to its smaller size will drive the strings above it harder than if it had to drive all six.

So if I can get the practical stuff to work, this is my next attempt at getting more magnetic power from the same current without compromising the high frequencies.)

cheers

Col

[psw]

Now that kind of strategy does have some warrant Col...that would be a far more obvious and productive kind of approach. The Hex thing was going to head into that direction, drivers built to optimize drive for a given string rather than driving it with a hex signal...in large part because of the interaction between drivers that occurs regardless of independent signals.

I gather the desire is to get more efficiency? Lower power, cleaner headroom, battery life...that kind of thing?

[col]

Now that kind of strategy does have some warrant Col...that would be a far more obvious and productive kind of approach. The Hex thing was going to head into that direction, drivers built to optimize drive for a given string rather than driving it with a hex signal...in large part because of the interaction between drivers that occurs regardless of independent signals.

I gather the desire is to get more efficiency? Lower power, cleaner headroom, battery life...that kind of thing?

That's the idea.

There are some potential problems that may or may not be difficult to deal with.

There will be some interaction between the two coils, changing their inductance values a bit through mutual induction. I don't know how to calculate this, so it will be down to building and testing. Unfortunately, I'm not a work-a-holic like you when it comes to building these things

I'm also concerned about the area around 300Hz (open high E string).

It seems like it should be good with both drivers operating at that frequency, and the overall phase shift and impedance at that frequency are ideal, but there may be some phase difference between the two individual drivers. I'm not sure how much, or what effect it might have, so 'fingers crossed'.

Interestingly due to the wonders of phase the current through the main lead will be noticably less than the sum of the two current values through the two drivers - even though they are both fed in parallel by that main lead. I suppose that when there phase difference has cancelled out some of the power, the effective value will be that of the main lead....

Anyhow, its all very interesting. Its a bit like the old idea of having 'woofer' and 'tweeter' drivers, except instead of being optimized to give an even amplitude response over a frequency range, they are optimized to give even impedance and low phase distortion.

BTW, you will love the fact that each coil will be using a different wire gauge - 0.31mm for the big coil and 0.23 for the small.

cheers

Col

[McSeem]

Another thing to consider is that a single, on-body mounted driver will have relative-to-string positions at the knots or near-knots of standing waves. For example, if you place the driver at exactly 12th fret, you can never drive the 2nd harmonic on an open string. And there's no particular position that will work with all frets. Double or even triple-coil driver definitely improves the things. Well, it becomes something like 3-way speakers, and who knows, maybe in 10 years true hi-fi maniacs will use tri-wiring/tri-amping to power sustainers. Just imagine 18 coils, 18 amps, and 36-wire cable for balanced outputs... ))

When I get all my stuff I'm waiting for, I'll try to experiment with dynamic harmonic equalization in DSP. I can analyse the spectrum right after the attack and try to preserve it as much as possible. I'm not restricted with compact in-cavity circuits, I'm not restricted with power, and of course, it will require at least a 13-pin Roland cable, or even a separate one. I'm only afraid that the coils may start smoking :-)

I also have a suspicion that rich, multi-harmonic sound may be obtained if you power your coils with very strong and narrow delta-impulses at the fundamental frequency, as it will simulate in some way your pick and/or fingers. But I'm not sure, it's just an assumption. I'll try to do that also, but I also realize, magnetic shielding may be a huge problem in this case.

[McSeem]

BTW, another crazy idea is to design a true stereo pickup, working in the same way the vintage vinyl pickups work. Each pickup consists of two tiny coils at 90 degree to each other and placed closely to the bridge, where the mechanical amplitude is not that high. There coils are connected to the right and left channels. The point is the polarization of string vibrations varies during the time, so that, you will have "natural dynamic panning" and some kind of natural stereo sound.

[Fresh Fizz]

Some interesting new developments!

I had similar ideas. Take thicker wire but keep the old amount of turns. Compensate with an extra resistor. Add a capacitor parallel across the driver coil to create a parallel notch. I don't know the English expression but this should multiply the current times Q at the resonance frequency. Phase shift at resonance frequency is 0 degrees. But at other frequencies it's not

Anyway, I've built a new driver.

2 x 90 turns 0.25 wire, 8.5 ohms, 1.8 mH.

There is a bigger gap between the blades than on the previous version, the blades are somewhat thicker and I used an iron bottom plate (instead of plastic on the previous one).

My first impression is that the new driver is a lot more efficient.

Loose plain E string swings a lot more.

Cheers

FF

[col]

Some interesting new developments!

I had similar ideas. Take thicker wire but keep the old amount of turns. Compensate with an extra resistor. Add a capacitor parallel across the driver coil to create a parallel notch. I don't know the English expression but this should multiply the current times Q at the resonance frequency. Phase shift at resonance frequency is 0 degrees. But at other frequencies it's not

Interestingly, the basic 8ohm 0.2mm single coil driver at 1.2mH combined with a 220u output cap has a (small) resonant peak at almost exactly 300Hz - just where we need drive to be most efficient !

Anyway, I've built a new driver.

2 x 90 turns 0.25 wire, 8.5 ohms, 1.8 mH.

There is a bigger gap between the blades than on the previous version, the blades are somewhat thicker and I used an iron bottom plate (instead of plastic on the previous one).

My first impression is that the new driver is a lot more efficient.

Loose plain E string swings a lot more.

Cool

cheers

Col

[McSeem]

Col, obviously, your amp has very low Z, so, the resonance is heavily damped and does not have any significant effect. In general, any sharp resonance is not good for the driver. What is good of it if you can only sustain one note? :-)

[McSeem]

Maybe there already was a discussion in the long thread, but just in case. Has anyone tried the following configuration? 1 or 2?

In theory it should vibrate the string not only up-down, but also left-right (with respect to the picture). Although, it will definitely take more space.

Edited April 28, 2010 by McSeem

[col]

Here's a femm plat that compares various conficurations of rare earth, alnico, with steel core, without steel core.

(This is just the permanent field, but it is very important.)

As was suggested earlier in the thread, you can see how magnets beneath a core don't work very well (unless the core is very short and compact).

This example also provides some insight into why I've had success with a 'humbucker' style layout.

cheers

Col

[McSeem]

This example also provides some insight into why I've had success with a 'humbucker' style layout.

Can you give me some direct links to your more detailed description? And have you ever tried a humbucker-like configuration, with two coils and the poles across the string?

[psw]

I used multiple magnet arrays in the Hex drivers to do essentially the kind of thing you are suggesting there...but there are some very unwanted side effects of this...alignment is crucial and bending strings unless it is mounted at the bridge is going to make these things worse. These are the reasons I put aside these things because a long with driver interaction anyway, the devices were complex to make, a little expensive and had too many unexpected problems.

Instead of multiple coils though, I used multiple magnet arrays exploiting the properties of rare earth magnets, but not pointing them at the strings and creating this so called "balanced field". The "coil" then only had to upset the 'balance' between permanent magnets to achieve just such a more 'natural' drive motion.

However, these ideas I used to obsess about early on...but once you make these things, hear the effect, see the problems and the expense and frustration building them...you realize that the expected bonuses are not there. They do not sound more musical or anything in reality.

...

Col, me and others put up a lot of designs way back with notions similar to what Col is pursuing now. The resource is again open to see a lot of this stuff, for those that really want to get into these things. I certainly liked the idea and tried to do this with the Hex things...but alas...happy to hand it over.

BTW, you will love the fact that each coil will be using a different wire gauge - 0.31mm for the big coil and 0.23 for the small.

Yes, I do. I'd assumed that they would be calibrated differently in that way. Everyone has different approaches and this could well be a way forward. I already suspect that some of my devices are more efficient in many practical ways than the commercial units...things like battery consumption for instance and the amount of power these SC are capable of delivering to the string if wanted.

I'm still not convinced for the need for dual coils...but there may be worthwhile aspects. I did notice a drop in bending strings between the two coils, but it isn't that bad...nothing like the sensitive and quirky hex drivers which have those effects on every string!

One of the last new designs I tried working on was a bilateral compact driver with internal magnets on a cheap telecaster...again, following the mid driver thing...ease of installation, choice of pickups, etc...

It wasn't a huge success I must say, but the design was a little compromised by the space requirements and ambitious in it's scope. It worked enough for me to discover that I didn't like it though!!!

The use of internal ceramic magnets in the core, as you earlier pointed out possibly compromised the design too much anyway...bad choice though Tim/onelastgoodbye made one that seemed to be good in a conventional SC format...had a big influence on my designs and approaches to construction.

The only thing that might tempt me back into dual coil drivers might be wafer coils on an HB pickup conversion...but that would be a long way off if ever.

I still have the feeling that you don't necessarily have to go the different wire gauges and such, more could be done with a stereo amp with different tonal outputs optimized for the string sets perhaps...that was more the way I would probably have proceeded, but then perhaps I wouldn't have got the efficiency you are shooting for.

Interestingly, the basic 8ohm 0.2mm single coil driver at 1.2mH combined with a 220u output cap has a (small) resonant peak at almost exactly 300Hz - just where we need drive to be most efficient !

Just as a note to my work, I almost always used a 100uF output cap on a LM386 circuit. One of the beauties of these simple circuits is what you can play around with so easily.

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BTW, another crazy idea is to design a true stereo pickup, working in the same way the vintage vinyl pickups work.

This is very much how the aborted Gibson bridge pickup system worked, might want to dig around the patents. Not as "good" as one might have hoped for 'on paper' I suspect.

And there's no particular position that will work with all frets. Double or even triple-coil driver definitely improves the things. Well, it becomes something like 3-way speakers, and who knows, maybe in 10 years true hi-fi maniacs will use tri-wiring/tri-amping to power sustainers. Just imagine 18 coils, 18 amps, and 36-wire cable for balanced outputs... ))

No offense, but this sounds like an absolute nightmare!!!

Also, while if may "seem" to be a problem, in practice you will find that it is not...at least with most conventional driver schemes. Remember, I tend to use a single 3mm steel core across all strings or 5mm alnico poles and I do not have the "problems" you are suggesting. The reality is that there should not be dead or hyperactive spots...the drive even with a core this small works over a wider area than a single point in the string, so it is not that effected by nodes and antinodes.

One might consider in this regard that when reversing the device, you generate harmonics, not stop the string as you might expect...

The idea that you need a tremendous number of coils seems naive to me. Now, Col I can see is working towards more efficiency...these are real tangible goals that would provide benefits. More efficiency means less power required, less power, less EMI problems, less battery drain, cleaner headroom.

The difference I sense is that many approach this thing with a sense of there being a "perfect" sustainer" or a "natural order of things" in relation to string vibration that must be preserved. This, even in the face of modeling and effects that are there to create musical effect that a good sustainer may well create organically by it's particular application, design or intention.

The end result is more and more complexity that brings more problems and in the end, is it actually better, if so, how?

The fact is that a very low mod, small cheap and effective device can be created that can sustain a string, control in that envelope and decay, as well as create harmonics and controlled feedback. Will you gain more from a complex system of coils and such.

When working in these areas it can be easy to get lost in things if the goals are not clearly stated. So, I have often asked and know from the past that Col has such goals and that they make sense.

I personally feel that in general, such a system would in some ways contravene my goals these things, so am not so keen for myself. I'd find it hard to make an effective system with dual coils or significant changes in design to work in as compact and versatile format as the kinds of things I have developed. I have had problems with such designs in the past and find them far more tricky to make and develop. So, I'd personally have to see efficiencies of the proposed 40% to take them seriously for myself and my own goals.

Bear in mind though, that I insist on low mods and no compromise of the instrument...I need that neck pickup and the guitar to completely function as it had. Now, if such a device is so big as to take up the space of the neck pickup...as the commercial units all do...then that alone would compromise things too much.

Lets face it, if I am getting days and even months of occasional use of the device and not compromising the guitar in any other way...even remarkably more efficient power consumption (and the commercial units do not achieve this even with their D-class amps and such) would be less convincing when the only cost is a few more battery changes.

This may in some ways explain a part of my "attitude" in recent times. A lot of proposals seem to lack stated goals, are based on suppositions of problems that are not borne out in practice, are extremely complex and in large part unproven.

I realized that I was doing this myself with the Hex devices, regardless of how "clever" they really had become.

If such devices as Hex systems are really that "better" what are the costs and promises they really hold? Is it a more polyphonic response perhaps that is dreamed of here? But, to really work you are going to have to have true hex pickups, perhaps not be able to use mag pickups at all...well, there is the Variax...but there are digital ways of achieving all this and more without such a device at all...since the guitar is already modeled completely...has to make you wonder. There is a use for it, if it is accepted that such a device may have a character of it's own...but then that makes something of a nonsense of the "pure vibration" notions that keep getting thrown about.

The electronics and power required to run such things is already enough to put most people off alone. People just don't want a battery in a guitar, they certainly don't want to ahve to plug it into a wall socket without significant benefits. The Variax sought to provide so much, that people would take that on board...but it has not scratched the acceptance of conventional electric guitars in the market for all that. I personally see a lot to offer in this kind of technology, especially in the right hands...but then If I were that way inclined, I'd be looking at digital solutions rather than electromagnetic mechanical things like a sustainer which are extremely primitive in comparison no matter how far they are developed.

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Just some thoughts...best to actually make some scratch devices of some of these ideas rather than debate them, and experience the problems and potential solutions you can come up with. But first, I think that a clear statement of goals and criteria are set out without assumptions of how successful devices can work. The reality is that many goals may already have been achieved.

I can see where Col is heading for instance, my goals have always been explicitly stated...not sure why FF needed to go the dual coil route and more power on that kind of single pickup guitar to get that effect, but it looks neat. I actually suspect that the dual coil bigger sustainer 'sound' a little different and may need slightly different circuit tweaking for best results. Col is more of an expert in that regard as my work has been more of a comparative nature.

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Phase shift at resonance frequency is 0 degrees. But at other frequencies it's not

I think the resonance frequencies of coils and devices are as crucial as the inductance and efficiency angles, so good to see it mentioned. I did try and measure mine but again, it is a tricky process.

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As there is still an apparent interest in these things and general discussion. I am considering being more active in sustainerland myself after the house move I am doing this weekend. I have even been considering a new format and perhaps new home for such things if people are interested. While 'the island' isn't the most electronics friendly as far as supply, I may well reactivate things like my circuitry and wafer coils for instance. I have at least one guitar in the works which addresses controls and shows the effectiveness of the wafer coil design (that is fully tested) and on a different kind of guitar to something like the Tele. In discussions elsewhere, a number of other ideas of interest have also emerged. For instance, an electromagnetic version of a tapping instrument somewhat like "the stick" is formulating as well as a fretless that has been in the works for some time. If plans for recording and performance in the new year pan out a bit, such instruments and applications of the electromagnetic excitation of strings and more elaborate approaches may well be on the cards in my neck of the woods.

I have to say that the choice of user name of McSeem is a little unseemly in the context of the last year...is that the best you could come up with to join sustainer discussions? Each to their own of course, but for me it colors my responses with unneeded caution, especially in view of the ambitions you are stating. Otherwise, although long, a lot of this kind of things was discussed in the Hex era in the early part of the thread, very difficult to repeat it after all these years

[McSeem]

My goal is different. I anyway want to experiment with hexaphonic mag and piezo pickups, audio interfaces, digital processing and so on. I'm not so restricted with power, batteries, equipment, and yes, with my budget. My goal is to try to get new unusual sound effects, based on analog source signals (not MIDI!), digital processing and feedback.

If you are so concerned about power consumption, why not to use class D amps? Analog Devices has plenty of them, for example:

http://www.analog.com/static/imported-file...ets/SSM2305.pdf

It's filterless (I suspect they use a bridge circuits internally), you don't even need a capacitor in the output.

There's no need for super-linear-class-A zero-THD amp. The quality, noise, and other parameters are not important for sustain drivers.

I have to say that the choice of user name of McSeem is a little unseemly in the context of the last year...is that the best you could come up with to join sustainer discussions? Each to their own of course, but for me it colors my responses with unneeded caution, especially in view of the ambitions you are stating. Otherwise, although long, a lot of this kind of things was discussed in the Hex era in the early part of the thread, very difficult to repeat it after all these years

:-))) I'm confused. What happened last year?

I've been using this nick for a long time, since I started my Antigrain Geomentry project.

[Fresh Fizz]

Maybe there already was a discussion in the long thread, but just in case. Has anyone tried the following configuration? 1 or 2?

In theory it should vibrate the string not only up-down, but also left-right (with respect to the picture). Although, it will definitely take more space.

So agg is your baby, nice to know!

I've built a hex driver that bucked the hum. N-S-N-S-N-S and adjacent coils out of phase.

Above the magnet it performs well but in between the magnets there is no sustain. That makes sense because in between the string got or pushed or pulled at the same time by the surrounding coils/magnets.

Your design would be: N-N-N-N-N-N-N (7x) and adjacent coils out of phase. In between magnets it would function like you explained. But if you bend the string across the magnet you get the old up-down orientation and depending on which of the 2 magnets it will be fundamental mode or harmonic mode. I haven't tried this, it could be useful. But I guess the guitar pickup has to replaced by a 2D type pickup . That looks like a problem to me.

Cheers,

Fresh Fizz