constant low frequency hum

[jeffreyperr]

All the voltages are good and all that. I'm Listing on HD650s. First off It sounds great. When I power up the amp I can hear a constant, low frequency hum that is not affected by volume. I unplugged my source and the hum persisted so I'm sure it's originating in the amp. Is it possible I wired something wrong or if that couldn't be the problem then what could I do to get rid of this hum!

[Paul Birkeland]

The first thing to do would be to reheat all of the solder joints in your amplifier.  In particular, those solder joints that hold the 220uF filter caps in place are particularly important for quite operation of the amplifier. 

Also, you can get decent voltage readings but terrible performance if the solder joint on the headphone jack where the black wires connect is not properly soldered.

-PB