NE572 as VCA?

[The Dark force of dance]

Y-ellow Juergen 'n' y'all.

I have to prefix this with... I have not messed with these things in, ooo,
about 8 years. My overall feeling when I got the CN2R MK II's to work was.
"I'm glad that's over with. I hope I never have to design another NR using
these things."

If I were designing an NR from scratch now I'd probably use one of the AD
dynamics processors or something. Then again AD don't have a real good
track record either.

>I'd be interested in this, too. I just bought a handfull of 572's a few days
>ago.
>I have compander applications in mind in the first place, so I'm curious
>if there is an error in this basic application, too ? (on the data sheet)

It's not so much an error as I recall but omissions or misleading
information. Something Signetics data sheets share with AD. Though I figure
AD are even worse. You can chase your tail for days trying to nut out
what's actually gone wrong. 

>And, most important: Is it possible to link two halves of a 572 for stereo
>compression ? I think it *should* be possible to hard wire the capacitor
>pins together, i.e. pin 4 to pin 12, and pin 2 to pin 14, and only one set
>of 2 capacitors. I've never tried it, but I will, unless (hopefully) one of
>you
>has tried this already.

I've not tried this but I can't see why not. I have this vague recallection
that doing this gets a mention somewhere. I just can't think where. What
you'd probably do is use the rectifier from one half and feed it to both
gain cells. Which BTW are only transconductace stages. Personally I'd give
a good ol' 13600/700 a go if you were doing something like that. Though I
guess the 572s are a tad less noisy than the 13600s. But if you were
building DNRs then use a 13600/700 definitely.

The thing is that you can use the rectifier to drive the gain cell even if
you are driving the whole thing with a DC control voltage. But you can
bypass the recdtifier stages completely if you wish.

I have no way of scanning and publishing my notes unfortunately.

Hope this helps.

Be absolutely Icebox.

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