Combined Gain and trim/level-ing fader design

[Microphoniste]

This for sure is a topic that connects to the stoneage of circuit design, but who knows… (edited on September 29th)

Which is your approach on the gain side of your preamp/recorder…
to capture performances where actors can be very low speaking and, out of the blue, shouting like hell in the next second.
In the (older) Nagra days, for instance, there seemed to be a way of combining the gain and level potentiometers… i presume…
so that lowering the level with the level fader meant also lowering the gain. Whereas, on the other hand pushing gain also - at some point - opens up a complementary gain, at the leveling /trim fader.

Of course there are some issues in applying intuitive fading curves. But it worked great and in a very sensitive manner.

 

[Microphoniste]

May be another way to deal with the subject is working basically with 2 controlled gain stages…

Quoting Samuel Groner, with a dedicated design… (pdf attached)
“Design D: D_r1.pdf
That’s an elaboration of the “shared gain” topology. I can give reference to Steve Dove for the basic idea. The gain setting with the linear pot is pretty neat (D_r1_gain_law.pdf). Loading of the first stage deserves some attention in this topology—see D_r1_loading.pdf. Overall a simple yet versatile and good performing circuit.

https://www.nanovolt.ch/resources/microphone_preamplifiers/index.html