[sdiy] Magnetic String Actuation

[Spiros Makris]

thanks for all your suggestions! I started writing a response to everyone
in the morning, but eventually got some supplies before hitting send, so
scrap that.
So I went on and got a spool of 0.3mm diameter enamel wire and went on to
make an electromagnet with about 500 turns on around a metal screw.
Came out 8ohms and 2.2mH. My amplifier module can drive up to 24W into this
little thing but starts cutting off after maybe 1-2kHz. Turns out 0.3mm is
pretty thin, anything above 0.5W makes it warm up. I even got some fumes
out of it!
I can hear the coil vibrate and my instrument's pickups listen to whatever
the coil is putting out (it's pretty loud if you point it towards the
pickup), but I can hardly get any sympathetic action. I *think* I got a
very slight vibration after fiddling around with it, but I'm definitely not
even close yet.
I'm not sure what I should try next? Maybe I need more turns (inductance)
to produce a stronger force? Could the coils' frequency response be way off
and that's causing problems?


On Thu, 8 Sept 2022 at 07:03, brianw <brianw at audiobanshee.com> wrote:

> Besides the fairly modern Sustainiac, there is also the vintage Roland
> GR-500 Guitar Synth. You could turn up the Release knob on the synth
> control panel, and magnetic actuation would keep the string(s) sustaining.
> I've never experienced this first hand, so I can't comment on how effective
> it was, but Roland has a US Patent on it.
>
> Even newer than the Sustainiac is the modular "cycfi research" family of
> products and systems. I think this is your best bet, according to what my
> friends are saying. Again, I haven't worked with these products yet.
>
> https://www.cycfi.com
>
> Brian Willoughby
>
> On Sep 7, 2022, at 11:20 AM, Mr&MrsAccount <hbissell at wowway.com> wrote:
> > There is a commercial product called "sustainiac" which is in the form
> factor of a guitar pickup. For starters I'd play with just a single string
> and then refine it from there.
> >
> > Harry
> >
> > From: Spiros <synth-diy at synth-diy.org>
> > To: synth-diy <synth-diy at synth-diy.org>
> > Date: Wednesday, 7 September 2022 2:02 PM EDT
> > 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 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 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 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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