I'm taking a chance that this is an obvious and dumb
question. So be it:-)
In researching the S-20R I looked at the circuits for
the S-40A and B, which were its successors. I've found a
puzzle, namely the first audio grid bias was changed from a
standard cathode bias arrangement in both the S-20R and
early S-40A to a grid leak bias in the later S-40A and
S-40B. Why? Grid leak bias is pretty rare in audio stages
and can reputedly cause distortion. Does anyone know what
H's designers were up to?
I can't find any other examples of grid leak bias in
audio stages.


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Richard Knoppow
Los Angeles
WB6KBL