by TomMcNally » Mon Mar 05, 2007 7:51 am
How is the hum when you have your preamp connected and the volume all the way down ? You really don't want to run a tube amp with no input, when testing, either short the inputs, or connect up a preamp. Open inputs are like antennas for hum.
If you're getting hum with the preamp connected, disconnect one input at a time until the hum goes away, then look for a ground issue. You'll almost always get hum when anything connected to TV Cable is connected, an almost always if a desktop PC is connected. There are ways to deal with this.
... tom