I'm having a little problem with my HOTUSB1.
It makes a really irritating buzzing noise via my little dot I+ when i use it as a DAC for my PC. Using my AD900s right out of the DAC is fine and the little dot I+ works perfectly out of the line out on my Creative Zen, hell it even sounds good via onboard out.
Could it be the HOTUSB1 is incompatible with tubes or does the issue lie elsewhere?
It sounds like some kind of "ground loop", if the sound is a hum that is....
If the sound is higher frequency like a squeal, I've hear monitors can cause that kind of noise and playing the DAC in a different location may help....
Do you use lights around the house with dimmer switches ????
Describe the sound exactly, on which channels, both ???? at any volume ????