DIY Scaled-up EBow-type Feedback Device

I’ve built rudimentary ebow using this schematic in the past. input inductor is 8ohm, and output is 50ohm. You can get radial metal core choke that work well for this on tayda/mouser etc. Or wind your own magnet coils!

LM386 is a common low power audio amplifier

ebow_amp_116

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@ElectricaNada Thanks for the Dayton transducers link. Those look promising. I recall @Rodrigo mentioning these in the Piezothing feedback instrument thread.

Looks like they need to be in direct contact with the material you want to vibrate. I’m curious if they are able to work with a small gap as well. I’m envisioning something where the vibration-inducing device (whatever that ends up being) could be moved in relation to the vibrated material during a performance. Or even better, a super lo-tech autonomous kinetic sound sculpture that is able to move the vibration inducer in relation to the material.

@dianus This is a great starting point for the circuit. Thanks so much!

I think I have everything but the op amp somewhere in the basement. Off to Mouser…

Making electromagnets is quite an interesting youtube rabbit hole! It doesn’t seem difficult to build a powerful electromagnet, and (thinking aloud) if power was applied periodically (rapid DC switching on/off = LFO square wave?) towards audio rate, then would whatever metal object was near the electromagnet vibrate sympathetically at the same frequency? I wonder if there is lag, ie how fast the electromagnet powers up & acts? An eBow has some lag - exciting a string is not instantaneous… Experimentation is likely the only answer…

Consider the hurdy gurdy bow. It’s nothing more than a spinning disk of wood with some bow rosin rubbed on the edges.

Also, someone posted a youtube of his mechanical exciter for tibetan bowls on this forum within the past year or so. That’s well worth a look if you can find it.

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You’re reading my mind on the hurdy gurdy. I was actually thinking about that for another project.

Yes. The rabbit holes are multiplying, as rabbits tend to do. I like the idea of modulating the electromagnet.

It has been awhile but I messed around with string exciters with Eurorack in the loop. It would be fun to try driving other objects. What worked best for me was using a permanent magnet wrapped with magnet wire when driving a string. I used an alnico rod magnet and 34AWG wire (1500 turns). The coil was driven with a DRV tile but any little amp will work.

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While I do like my eBow, the “static” sound of it is one of the biggest issues I have with it. A wave shape hack for an eBow would be amazing.

Or, a multi string exciter with assignable wave shapes for each string.

I don’t think it’s made anymore, but I think Moog had a guitar that did something like that. Or it might be another company that I’m thinking of, that had this attachment for an acoustic guitar that worked on a similar principle but created “other” tones too.

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@pulplogic That’s super cool. Thanks for posting.

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yeah, the moog guitar, which paul vo designed… 2008 or somethig. it was pretty fun.

Ah right, had no idea it was the same person.

It’s a shame that kind of thing didn’t get more traction. I guess it’s a pretty niche thing.

There’s also this sustainer called The Gizmo which used rotating wheels and spring loaded levers to excite the guitar strings

Gizmotron1

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there’s also the duofluctus by sergey filatov, which produces sound from two strings being resonated by an alternating magnetic field, created by magnets on a spinning disc, which is then amplified via two pickups for a nice stereo effect.

I was very inspired by the duofluctus when making a sound sculpture built into a pillar together with a friend and collaborator last year. It had no microphones or pickups, only the box for acoustic amplification. this is what is looked like:

here’s what it sounded like: https://vimeo.com/373890551

the speed of the spinning disc enhances different overtones. the duofluctus has a knob which changes the speed. the sculpure I made had an arduino built in which varied the speed on the motor.

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WOW! this is a great idea. You could probably also play a normal electric guitar with a similar spinning disk with magnets as a handheld device.

it is, isn’t it! sergey also made a small handheld device he calls magnetor using the same principle which can be seen in this video: https://vimeo.com/326150192#at=45

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So the magnet is pulling at the strings each time it spins past, causing them to vibrate? Sounds amazing in the video.

exactly. very simple but clever design. glad you like it : )

ghost of thaddeus cahill