mr coffee said:John,
Thanks for reply.My bad. VCR2N.
http://www.vishay.com/docs/70293/70293.pdf
Yes - that's what I meant. Heard it used that way, just never learned how to spell it :
I'm familiar with that concept about total noise being dominated by preceding stages, but I was wondering if that might still mean lower total noise in a cascaded topology? Please correct me if I'm wrong here, but if the first JFET attenuator and recovery amp stage has much lower noise (because the series resistor - maybe 3K ish - and the JFET resistance is much lower) and then that signal, including the noise added by the first stage recovery amp, is attenuated by the second series resistor - again 3K ish - and JFET resistance which also has a much lower resistance than the classic design, couldn't the overall aggregate signal/noise end up being lower? Maybe something other than a equal recovery gain in each stage?
Might there be additional virtues if the two cascaded stages had their own side chain with a fairly low gain reduction range (maybe 10 db ish apiece), in terms of smoothing gain recovery and "prettier" sounding abrupt gain reduction transients? Seems like I remember something about Dolby C doing something along that line somewhere in the deeper recesses of my mind ;D
I searched for the Cordell AGC, but not sure I found what you are referring to. What I came up with was an oscillator using a JFET to adjust the gain of the Wien Bridge oscillator in a variable audio sine wave oscillator circuit as an improvement over the old light bulb trick . Looks like it handled maybe 6db maximum attenuation.
http://www.cordellaudio.com/papers/thd_analyzer.pdf
page 6 of the PDF 39 of the original Audio article.
sorry if you don't like it. I did. BUT I don't like distortion.
JR
I have played around some with THAT VCAs, and have appreciated their wide range of attenuation and gain, and maybe I should just concentrate on developing a compressor circuit around them. Best practice is best practice.
I think what attracts me to the JFET as a voltage-controlled resistor in a voltage divider as a gain element is the impression that the JFET overload behavior might have a desirable character or sonic signature, ...which might or might not pan out.
Again, thanks to all for the stimulating discussion.
mr coffee