[ARC5] Request for info - modulator cct using 6AG6 in class "B".

[mac via ARC5]

Leslie,

Yes, you mentioned an "unmarked pentode" stage in the audio chain.   
Sounds like, maybe, an "output limiter" circuit.  The scheme involved  
rectifying audio from later
stages in the speech amplifier/modulator and feeding back a filtered,  
negative bias voltage to the suppressor grid of an amplifier tube near  
the head of the audio chain.
The goal here was  an automatic gain control loop that followed the  
average, not instantaneous, variations in speech amplitude and thus  
overcome the operator's
speaking volume variations.  Found some information in a 1946 RAHB on  
a  circuit to do this but don't remember widespread application in ham  
designs of the period.
See anything that looks like a rectifier down near the output end of  
the audio circuits?

Also remember seeing something like this in a Navy TBK.

Dennis DuVall, W7QHO
Glendale, CA

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On Sep 19, 2015, at 3:36 PM, Leslie Smith wrote (in part):

>  somewhere in this I find a circuit that I'm (pretty certain) seems  
> to act as an overmodulation device.