🚀 go-pugleaf

In article <1752@c3pe.UUCP> maugorn@c3pe.UUCP (Steve "Maugorn" Haug) writes:
>
>...  Is this thing JUST a battery powered electromagnet? Or is
>it, as I suspect, an oscillator hooked up to the current going through the
>electromagnet?  What frequency(ies) of oscillation might we be talking about?
>I have made this effect by holding a small speaker with the output of the
>guitar coming out of it up to the pickups.  This is easy, the guitar will
>feed back and resonate on it's own peaks and the frequencies to which the
>strings are tuned/fretted.  How does this thing induce resonance without
>being dependent on the output or knowing how your guitar is tuned or what
>note you are about to play?  

Very easily, presumably; the same way that variable-frequency oscillators
work without knowing in advance what tuned circuit will be connected to
them. Negative resistance: you need only overcome the built-in loss in
the resonant element (be it LC circuit, crystal, or guitar string) in
order to get it oscillating steadily. Indeed, Steve was doing this too in
a roundabout way with the feedback configuration, although the coupling
there may have been acoustic rather than electromagnetic. But it's no big
deal to build a circuit with a pair of electrodes that will oscillate
when any of a wide range of resonant devices is connected across the pair
(I've done it countless times, and not always deliberately); doing the same
thing with magnetic coupling would be only slightly more complicated.

After all, if the resonant string is magnetically active and placed near
a coil, it will induce a resonant component in the coil's impedance, just
as it would induce a resonant component in the impedance of an acoustic
transducer as well.

As Jack Palance says, "Believe it -- or not!"

Max Hauser / max@eros.berkeley.edu / ...{!decvax}!ucbvax!eros!max