• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Please review EL84M PP design before I order parts.

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leadbelly

leadbelly

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Joined 2002
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Just hoping for an OK from the cognoscenti before I start ordering and working the aluminum. Nothing novel in the design but I am not working from a schematic and would appreciate a critique (not "LM317's s***!" but more like "that's unlikely to work properly" 🙂 ).

Tubes are Russian EL84M, will be set up UL. Am building just the power stage, as input stage aleady complete in own chassis.

PS will have SS diodes, plus a Morgan-Jones-version LM317 regulator, B+ approx 300V.

Planning to use local feedback with a 100K resistor; not OPT tap, because input stage in different chassis and would like to connect them via standard 3 pin XLR.

Also plan to bias the tubes at 70 mA/tube a la Allen Wright with a (shudder) LM317 CCS.

Lastly, for the heaters, since my power xfmr has a single 12V winding, I was planning to SS rectify to a single negative rail, and then from that rail power both the LM317 cathode CCS and also LM337 (not typo) CCS's for the heaters.

Whaddya think?
 
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