How Much DC is OK on a Power Line?

Actusreus, I sent you an e-mail message.

Chris, you can reach me by e-mail at [email protected]

Peter, what model Classe amp do you have ? A lot of later production CA-XX0 series amps have DC blocking circuitry, and for earlier production models that did not have it, the DC blocker circuit board was available as a retrofit.

A couple hundred millivolts of DC is all it takes to cause transformer hum. Abnormal high voltage and harmonic distortion can also cause hum. DC blockers will not eliminate hum caused by harmonic distortion.

DC can be caused by a variety of devices, including but not limited to light dimmers, appliance speed or temperature controls, washing machine motors, refrigerator and air conditioner compressors, etc.

The PS Audio Humbuster and Channel Islands XDC-2 AC filter should eliminate most transformer noise caused by DC. There is also the DIY option. I've done DC blockers for a few Audiogon members at a fraction of the cost of the "big boys".

As mentioned above, DC can come from a neighbor's house. It can also be generated in your own house. I would investigate in-house sources before looking for a solution. Look for possible sources, shut off all breakers and see if the noise goes away.

I don't know of any power company DC spec.

Pcoombs, harmonic distortion and DC are two different phenomenon. A UPS or power regenerator like one of the PS Audio units should cure harmonic distortion issues.

Peter_s, I said in my post above that as little as couple hundred millivolts of DC can cause a transformer to hum or buzz.