Suggestions for DAC isolation?

if you are using a berkeley alpha dac that is normal. below is a quote from a review in which michael ritter explains...

"What Michael told me only solidified my belief that sound quality was the foremost concern of the Berkeley Audio team. He explained that the Alpha DAC has two totally separate power supplies for digital and analog, and two power transformers. The dual bobbin transformers used in the Alpha have very high isolation between the primary and secondary windings that provides maximum immunity from line noise. One side effect of this high isolation is a narrow area of magnetic field that causes the bottom of the DAC to hum a little bit. Berkeley Audio Design could have opted for an absolutely silent solution at the cost of sonic degradation. Listeners will be happy to know the hum is inaudible when listening to music even at the lowest volume the Alpha DAC is capable of producing, 0.1 dB."

I've only heard of one manufacturer who openly stated that one channel of their DAC will hum and that it couldn't be heard once music was played. That was Valab.
Now that they have the power transformer in a separate case, their is no noise at any volume setting with no music playing. Toroids are notorious for their nasty sounds and interference unless properly shielded. Heed all the advice given above until something works.

Very interesting Richard_stacy, thanks.
It is a Berkeley Alpha DAC. Any other users?

I like the sound quality of this DAC, one of the best I've heard, so no plans to get rid of it.

rja...mine will be here end of this week. i am very anxious to get it! what digital cable/power cable do you use with it?

I've been through a lot of digital cables in my day. Right now I'm happily using a Kubala Sosna Emotion 1.5m XLR cable that I bought used here on Audiogon. I'm not sure how critical it is with the Berkeley though.