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mjock3 wrote:I to do an update for the sake of others that may have a hum problem as well as for Roy's name sake.
After doing the shorting of the inputs to eliminate the preamp from the equation, I came to find out at least part of the hum problem was caused by a CAPS 2 music server I had put together. When I unplugged the USB from music server to DAC the hum stopped. After a period of time I narrowed it down a bit more. I had hooked up a digital antenna to the CAPS server for recording some TV. (That is a no no but I did it anyway) When I disconnected the antenna the hum decreased but was still there on a low level. So I came to find out there is an isolation transformer that is used for cable TV. I bought one and hooked it up and all hum is gone!!
Hope this might help someone digging to find out how to solve a hum issue.