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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)

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

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.