MOTM

The diode filter in the GX-1 VCF (MOTM-485) exhibits severe IM (intermodulation)
distortion (around 22%!) at mid-to-high resonance settings. Here is a simple
sine wave sequence (MOTM-300 driven by MOTM-650 MIDI-CV prototype), with no VCA.
2 MOTM-485 VCFs in series (LP>>HP) do all the filtering/distortion. The LP
stage's resonance is modulated by the Velocity Out of the '650, and the CV MOD
depth (reversing attenuator) of the HP section is hand-tweaked as the sequence
plays.

Recorded in real-time (no dubs/edits): MOTM >>>Yamaha 02R/96 (with internal
delay)>>tc electronics M3000 reverb.

http:///www.synthtech.com/demo/485_sine.mp3

Paul S.

Hey all--

I mentioned to Paul that I'd bought a Yamaha SY-2 along the way (in case the
MOTM-485 didn't come to market) for that SY/GX sound. I discovered another
interesting effect in the SY-2 filter-- at high resonance, changing the
pulse width of a rectangular waveform without adjusting the frequency
produces these interesting step-wise changes out of the filter, as though
minor changes in the harmonic structure of the wave (i.e., by changing the
PW) have a substantial effect on the behavior of the filter. At first I
thought something was working wrong in the SY-2!  :-)  It's an unexpected
effect, I suppose, but one that I happen to like...

Frank,
who's looking forward to MOTM-485s...

-----Original Message-----
From: Paul Schreiber [mailto:synth1@...]
Sent: Saturday, August 07, 2004 10:32 AM
To: synthDIY; analog heaven
Subject: [motm] Demo of IM distortion in GX-1 VCF


The diode filter in the GX-1 VCF (MOTM-485) exhibits severe IM
(intermodulation)
distortion (around 22%!) at mid-to-high resonance settings.