• 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.

300B SE Hum

I am working on your standard SE 300B With DC heating and Potentiometer controlled input. It is very quiet at lower volume. As you turn it up it has a hum that gets louder and louder as you increase volume. Is this normal? It is quiet in actual use with 96db speakers. Using it with a pre amp means turning the 300b up just enough to get a good volume and using the pre for the rest of the amplification.