• 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.

SOund of 3B28 vs. 866A

ak_47_boy said:

The 866 will also need a few minutes warm up time where as the 3B28 does not.

Nah ... 10-30 secs are enough if you use the tube every day. Warm it 1 hour or more after the first installation before applying any high voltage. If it doesn't light up after a couple of attemps and it keeps on blowing your fuses just forget it, sometime it happens with MV rectifiers.