Etherwave Theremin Mods

[Harry Bissell]

I'm modding an etherwave theremin. Wanted to share tips...

1: I'm installing an octave divider. The etherwave audio is about 500mV
pk-pk.
I tried a CMOS "linear" amp using the 4049UB, with three stages cascade,
470K input and 10meg feedback.

BIG BOO-BOO !!! This is a BAD thing. First off, it draws a whopping
20mA. Second, while it does amplify, it is prone to oscillation at the
transfer point (1/2 Vcc). And in the nasty RF environment of the
etherwave, it oscillates big time.

The next stages cannot trigger on this. And you can't filter it because
it is right at the trigger threshold. CMOS schmitt triggers just "clean
up the oscillation. Result, a nasty ass distorted noisy ring mod kind of
sound... Maybe like the vibrators on steroids...

I used the 4040 divider to get the octaves... each sucessive divider has
a lower noise spectrum.... but nasty!!!

I trashed this and used a LM311 with a 470K input and 10meg for
hysteresis. No problemo !!! Now the trigger works perfectly.

The VCA in the etherwave is seriously overdriven. so when I inject the
dropped octaves they nearly disappear. UNDERWHELMING !!!

Tomorrow I will re-build the VCA so that it is cleaner and can pass the
more elaborate waveforms. I'll bring the result to the AHMW2000.

Just wanted everyone to know that the linear CMOS trick sucked... IMHO.
I just wanted to try it once in my life to say I did it. I won't do it
again. Honest !

H^)       (My new sign... replaces :^) Harry)