Transformerless Varimu Compressor

[gyraf]

..look for AGC (automatic gain control) in consumer tape recorders..

 

[Schmilsson]

Cool, you mean like those 'portable' 1/4" r2r?

 

[emrr]

I'm gonna dig this one up again simply because I like the prospect of an SE vari-mu so much.

there were many many single-ended types used in PA applications.

Examples? I'd love to eye a few schems.

Find any of the RCA PA amp schematics from the 1940's and 1950's.  Many of them have a single 6SK7 for GR.  Nothing special; just build half of the standard PP, then play with coupling values (bandwidth) and time constants to get acceptable results.  Most were simply designed as 'ceiling' safety valves, to reduce distortion level at max drive.  Don't know any model #s offhand; look at the Riders PA amp info, and other similar sources.  There are also some modular RCA pieces that are usually described as film pieces, which have 6SK7 based inputs with remote gain control that are in the same ballpark, in terms of control capability. 

 

[Schmilsson]

Cool, thanks, more neatness to dig into. I slapped a half 436 together the other day, didn't get it to work yet, but the more prospects to learn from, the merrier.