AW: Re: PCB for MAT-04 VCA

[Haible Juergen]

> Second, on a whim I
>      swapped out the MAT-01 matched transistor pairs and put in four
>      randomly-chosen 2N2222A transistors instead. No change in behaviour!
>      Absolutely identical performance. So - no expensive parts at all, just
>
>      six cheapo transistors and two TL082's. You can keep the layout the
>      same, Chris, as far as I can tell you can still stick four NPN's in a
>      14-pin DIP footprint if you don't want to buy MAT-04's.
>

Gene, thank you very much for faxing me the circuit!
Looks pretty much like a balanced modulator like the 1496.
Audio signal fed into the linear input, and the other input
used in a nonlinear range.
I think there was a VCA chip that worked by that principle,
the number was (ironically) 3340. Don't remember the prefix,
but it was not "CEM" (;->). It was used in the Sennheiser
Vocoder for mixing Vocoded and direct signals, if memory serves.
I got a data sheet for this 3340, and I vaguely remember that
distortion and noise was excellent with 0dB gain, but distortion
would increase with lower control voltages.
So, well, this is a different chip of course, but the working
principle is the same.

First response in the morning - have to read what you guys
have found out last night

later

JH.