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    Building, troubleshooting and testing of these amplifiers should only be
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Triode St70 with hum


2013-03-02 3:07 am
Thanks for the questions, here's more info and I've attached a pic.
4 JJ EL34; 1 Sovtek 5AR4; 1 JJ ECC82; 2 SED-EF86 Winged C
As a note, I have replaced the JJ with Ruby EL34's and the hum is louder.
When I first built it, I had to replace the 10 ohm resistor that went from the EL34 socket to ground on the right channel, since it was dead - no burning or physical damage.
I've examined all ground connections and can't see any cold solder joints or other issues.


  • St70 1.jpg
    St70 1.jpg
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