[sdiy] Interesting VCA circuit on MAT04 schematic

[Aaron Lanterman]

http://users.ece.gatech.edu/~lanterma/sdiy/datasheets/transistors/mat04.pdf

Check out Figure 9.

The MAT04 is used sort of like... wait, this is weird. It looks like the 
"lower half of an OTA," as in the VCAs on Rene's site - but everything is 
switched around. The control is going in what I usually think of as the 
audio input; and the audio input goes in what I think of as the control 
input, but not before it goes into... oh wait, are those OP-41 and 
2N2222's facilitating logarithmic conversion to cancel out the expo?

And there's a copy of that structure. Interesting!

Is this some kind of souped up Blackmer cell? The datasheet says it's 
"widely used in professional audio circles."

- Aaron

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