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.
I have a current meter under the cathode of my se 300B. As this is in the signal loop I wonder if it has any influence on the quality of the sound ?
Did anybode test this in the real world ?
If it was a particularly noisy DVM it might just inject sampling spikes back into the audio, but I doubt it. A moving coil meter certainly won't upset anything.