We had a similar situation.
I hung oriental rugs on the side walls and behind the speakers; got
heavier drapes for the windows; and installed these in corners where
walls meet the ceiling
http://www.amazon.com/Primacoustic-Cumulus-Broadband-Ceiling-Corner/dp/B001VO4EZ6
I also did a lot of
Try reversing how the SBT's power supply is plugged into the outlet.
Sometimes switching the plug polarity will get rid of a ground loop.
If that doesn't work, try using an optical cable between the SBT and the
DAC instead of coax.
If your DAC doesn't have optical input, you could get an optica
Is any of your equipment connected to a device that is connected to
cable tv or satellite (e.g. TV, cable box)?
If so, try disconnecting the cable tv and/or satellite coax and see if
the hum goes away. If that's the cause you can buy a ground loop
isolator that will usually cure the problem.
A
