John,
Thanks for reply.
google does not help me find a data sheet for VR2N ??
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 :
When cascading gain stages the total noise will be dominated by the earlier stage since the later stage amplifiers the earlier stage noise too.
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
Mature technology and well vetted. Look up Cordell's AGC for best JFET practice (IMO), but best practice for a modern compressor is latest THAT VCA.
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.
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