[sdiy] Mag sensor as a CV source

[jhaible]

> I've been playing with a linear hall effect sensor
> and a magnet on a string as a wobbly LFO.
>
> More details than you care about and a cheesy
> sounding wav file are at the unlinked page:
> http://www.seanet.com/~tpaddock/mag2cv.html

Looks nice !

I have recently used a hall sensor for the first time myself,
for my latest (JH-720) synth project that uses this old
SH-2000 keyboard action. The after touch sensor was
a hall sensor originally, but it was broken, and I had to replace it.

I used a generic (passive) type which I found somewhere in
a drawer, just run 20mA thru it and get a few mV differential
output. A single OP-07 would bring it to useful levels.

This thing is so sensitive that you can really make manual
vibrato on the keyboard. The trick is to apply some "bias"
force to the sensor on some note with the left hand, and than
slightly increase the total pressure with the finger of the right
hand which is playing the note that shall sound. (with top
note priority, that is)

JH.