• 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.

Tube amp buzzing with very high frequencies hisses

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#22
flo777 said:
The capacitors were changed with the same values as the originals.
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And the same type as the originals? That matters too.

People swapping electrolytics for film caps sometimes find that the electrolytic ESR was damping a resonance, so the circuit is unstable with a film cap.

People swapping cheap film caps for 'audiophile' film caps (e.g. polypropylene) (or foil caps) sometimes find that the larger caps now add more stray capacitance so more hum pickup or more capacitive feedback - so instability.
 
#23
I moved the RCA grounds to the proper location, but they still contact the chassis directly. I may have to install different RCA connectors than the originals, and hopefully that will fix the issue.
I only changed the electrolytic caps with the same value as the originals.
 
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