[sdiy] Magnetic String Actuation

Spiros Makris spirosmakris92 at gmail.com
Wed Sep 7 20:39:13 CEST 2022

String exciter was a good idea! I found this blog post
https://frankpiesik.wordpress.com/2020/04/02/gregs-harp/ Unfortunately, the
amplifier is not shown, but I think I can make something similar to that
wound coil and give it a try. I can get a TPA3118 amplifier module locally,
let's hope it will be enough to get at least some faint movement.
I'm not entirely sure how I should drive them, starting with a square wave
on the string fundamental frequency makes sense?

On Wed, 7 Sept 2022 at 21:29, grant musictechnologiesgroup.com <
grant at musictechnologiesgroup.com> wrote:

> There are several ebow "clones" out there. I know I've seen a few on
> Indiegogo and Kickstarter, but this is the only one I could find with a
> quick search:
> https://www.kickstarter.com/projects/38513516/wond-the-string-exciter-sustain-and-control-in-you
> So maybe string exciter is the term you need. Also worth a listen is the
> famous Gizmo (the Gizmotron). It's being reissued.
> https://www.guitarplayer.com/gear/it-promises-to-revolutionize-the-world-of-music-watch-this-rare-vintage-news-report-on-the-gizmotron
> GB
> ------ Original Message ------
> From: "Spiros Makris via Synth-diy" <synth-diy at synth-diy.org>
> To: "synth-diy mailing list" <synth-diy at synth-diy.org>
> Sent: 9/7/2022 10:54:50 AM
> Subject: [sdiy] Magnetic String Actuation
> Hello, list,
> I am interested in experimenting with magnetic string actuation. That is,
> use an electromagnet to induce vibration to metallic(?) strings; the
> opposite of what a guitar pickup does typically. I have seen this concept
> realised in a couple of different applications:
> 1. Magnetic Resonator Piano <http://instrumentslab.org/research/mrp.html> is
> an electronically augmented piano that can do cool stuff such as real
> crescendos, electromagnetically dump strings, produce overtones etc. Every
> sound produced comes from the strings themselves.
> 2. Ebow <https://www.thomann.de/gr/ebow_ebow.htm> is an electromagnetic
> actuator for the electric guitar. Place it close to the strings and they
> will start vibrating, similar to the way they do when using a bow.
> 3. Moog Guitar <https://www.soundonsound.com/reviews/moog-guitar> contains
> some sort of actuator and suitable circuitry to make it infinitely sustain
> notes, apply active damping and more.
> I bet there are more if we start digging, but these are some examples I
> can think of off the top of my head. Unfortunately, I don't have enough to
> go on here and decide on what kind of hardware I need to produce this
> effect. The magnetic resonator piano researchers have published a couple of
> papers that go over the fundamental equations involved. Still, unless you
> can really wrap your head around them (I can't) it's not enough to get you
> going.
> I obviously need some electromagnet, either off the shelf or custom wound.
> Then I need an amplifier that can drive enough power into it, in the
> correct frequency range.
> Aliexpress is full of various electromagnets. How could I decide on a
> couple that might be promising and give them a try?
> What about output amplifiers? I know the basics of driving speaker coils,
> but my guess is a strongly inductive load like an electromagnet is going to
> be a different story.
> I've been thinking about this for the past 10 years and still didn't
> manage to figure it out. Any kind of info or advice you could share is
> invaluable!
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