During all the rumblings about console automation (Allison, Olive, etc.) in the early seventies, I had the inspiration for Compumix (based on years of working with telemetry systems) while I was chief engineer at Quad-Eight. But the hardest part was finding a good VCA. I had developed a novel PWM/PAM unit - it converted input audio into 1 MHz PWM (using a single transistor and a TTL Schmitt trigger IC) and then used a pair of complementary MOSFET switches to modulate the PWM's amplitude in response to the DC control voltage. Then a simple low-pass filter recovered the audio. It worked really well, including a low noise floor, but it was hard to get the zero-control-voltage output to under about -80 dB because N and P-channel MOSFETs of the day were awful compared to what's available today. We made about a hundred of them (I still have one as a souvenir) that were used as sub-group faders on a few large custom boards back in the day. But the trimming required ruled them out for the Compumix system, so I was told to reverse-engineer a dBx 202 and we made our own version of the module until dBx became aware and Quad-Eight got the customary "cease and desist" letter from dBx's attorney. They were gracious enough to give us a favorable quantity price and we used the 202 in production Compumix systems. Compumix, an "add-on" mixdown automation system sold well - to A&M, Warner Brothers, Armin Steiner, Neil Young (who cut his "Time Fades Away" album directly from multi-track via Compumix), and many others. Compumix's "update" function apparently established a standard for using -15 dB as a reference point for updating a track's gain trajectory. Bud Bennett, owner of Quad-Eight back then, was notoriously stingy but, to my astonishment, gave me a bonus of half my yearly salary that year for developing such a successful product! It certainly wasn't trivial back in the day before floppy discs and single-chip processors!@ CMRR many of us in the industry are well familiar with the history of THAT corp, and before that DBX going back to Dave Blackmer's early VCA development. Dave was working at API at the time but reportedly they weren't interested .