Also, the hum goes away when grounded only when put my hand near the wires. Moving the wires also helps, but replacing with a resistor didn't help, as I mentioned
An input signal might destroy the conditions for oscillation.
Unexplained hum (or distortion) which disappears (or appears) with signal or when you wave your hand near the circuit is a classic symptom of parasitic oscillation. Have you used grid stoppers?
Unexplained hum (or distortion) which disappears (or appears) with signal or when you wave your hand near the circuit is a classic symptom of parasitic oscillation. Have you used grid stoppers?
You say this is in the prototype stage, ...breadboarded? Are you using a ground buss line in place of a chassis ground system? Are your input jacks grounded to that or is the shield line/ground side just floating on the end of the input line wire? With the inputs hooked up to play you are grounding them to your source device and providing a lower input impedace to the driver tubes. You cannot expect open input lines to be noise free. They act like antennas and can pick up small EM signals and your hand can supress that or add to that depending on the environment.
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