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How can I make a sustainer for an acoustic guitar (working on the principle of an e-Bow)? Answered

I mentioned acoustic sustainer because I have been told it is easier to build than an electric sustainer. I have been told that piezos can be substituted for a normal mag p/up, then use a monophonic coil driver and the amp/preamp and AGC (Automatic Gain Control) to even string response. But I have had difficulties with the PG Sustainer thread instructions, particularly for acoustic guitar. There are various amplifier and preamplifier circuits available, but I am a complete novice to electronics. I have a more knowledgeable friend who is able to work from circuit diagrams, but I need to be very clear about what I want him to do, and need also to be able to access the components. Thanks in advance for your help.


I built one in 1982 and spent months at the patent office searching. After searching every "lute type instrument" patent as they were called back then, I found that "Mr. Heet" of "ebow" fame had patented it for both the portable ebow as well as the onboard system for electric guitar. His patent was from the 1970s so I'm not sure why others can claim a patent on the exact same concept.

With the drop in prices, and availability of used equipment, the easiest way is ti just buy a foot pedal with the feature(s) you want. I picked mine up for $20 ...... and you would spend that much, or more, to build something (with a single use) to match it.

I am not sure which pedal you are referring to which has such an effect. I presume you are talking about a compressor? How would that work with no amplification? How could an external pedal effect cause the strings of an acoustic instrument to vibrate and sustain acoustically?


9 years ago

You should probably ask for help on the Project Guitar Forum topic you reference ("Sustainer Ideas"), since the folks there have been studying and hacking the problem for some time. I gather that an acoustic sustainer is easier than an electric because the driving coil might interfere with magnetic pickups, but not with piezos. Without having tried to build one (or even having thought about it much), why is an Automatic Gain Control necessary? You should be able to control the gain simply by moving the driving coil closer or farther from the strings (once an overall gain control is adjusted.) After all, isn't the whole concept of the EBow itself essentially an expression controller? Why make it automatic?

Thanks gmoon. You are quite right about IMF caused by interaction with magnetic p/ups.

The AGC has been found to be necessary precisely because unlike the e-Bow, the driver cannot be practically brought closer to the strings nor swept from the bridge to the neck in order to find better nodes - because it is fixed. What people have been finding is that the output is weaker from some strings - particularly the higher strings - than others. Hence the necessity for the AGC.

What I actually want is to have a sustainer (which is based on the e-Bow technology), mounted on my acoustic guitar, but preferably with the option to remove it and put it on another instrument.

People are helpful on the forum, but not all that many are successful, and having spent some three years there without gaining sufficient information for my specific needs I am now trying elsewhere.

In fact what the Sustainer thread needs is someone with the kind of skills displayed here to do a step by step tutorial using multi-media presentations - that is what I am hoping someone here is going to decide to do! In fact it would be really great if a guitar tech were to collaborate with an electronics tech in order to really define the subject in a thorough and ordered manner so than it can be duplicated by anyone with basic soldering and DIY skills.

Regarding being an expression controller, that could be said of the e-Bow, but in fact the greatest expression comes from having both hands free to do what they should be doing, rather than having to hold something as clumsy and unwieldy as an e-Bow, which thus tends to limit one's expression and guitaristic technique is compromised severely.

I see, that makes sense--although you're really designing a whole new instrument ;-).

What you call "automatic gain control", I'd call a form of compression or limiting. I've built them in the past, using opamps and an LDR in the feedback loop.

Can you point me to any pages with more specific examples of acoustic sustainers, or your own efforts? The "Sustainer Ideas" thread is 295 pages long... I'm curious, especially about the driver for the acoustic version.

PM me if you'd like to collaborate...

Thanks Gmoon, first of all please accept my apologies for such a belated reply - I only received notification of an update recently.
it seems that unfortunately the Sustainer thread has been put to rest....there was some discussion specific to acoustic sustainers, but to be honest there was very little interest on the whole. Hence my posting the question here.

There is very little information on the subject, although the consensus was that such a project would be considerably easier and more simple than an electric guitar based sustainer, because of the problems faced when interfacing with magnetic pickups, especially multiple pickups.

The acoustic version only needs to get the strings vibrating acoustically and cause them to sustain. This effect could in turn be picked up and amplified with a normal piezo bridge pickup or whatever, but the idea is to produce a very similar effect to that of an eBow on an acoustic guitar, but across all the strings simultaneously. The effect of the eBow on an unamplified acoustic guitar is perfectly audible and quite loud actually. Very subtle too, as one would expect, and I believe very usable too...

I realize that the eBow only works on nickel strings, and has very little effect upon bronze or brass strings, but I could work with that. What form of collaboration did you have in mind?

In terms of my own efforts, those are unfortunately limited to my experimentation wtih an eBow on the acoustic guitar. It works on the nickel or steel strings, but has little effect on the bronze or brass wound strings because of their lack of magnetic conductivity I imagine.

The eBow was also very slow to take effect, but once it did the result was surprising, at least to me, as it was able to drive the strings into sustain with no amplification whatsoever.
This is what got me thinking about this idea of having the effect available across all the strings, but without having to physically hold and control the eBow or something similar.
However another problem that would need to be addressed is just where the node needs to be for optimum effect on the strings. I imagine that it would be in the equivalent position of a neck pickup, where the node produces the strongest effect on an electric guitar, but I am guessing here. Look forward to discussing this in more detail perhaps. Thank you again.

I would be very happy if someone posted an instructable for an acoustic sustainers. Just sayin...

The sustainers thread is filled with lots of bright sparks but its difficult to find much clarity amongst all the new revelations, updates and changes being noted.

I make custom guitar sustainers & can readily make anyone a sustainer for acoustic - get in touch if you're interested.