How Much DC is OK on a Power Line?


The other night my Classe amplifiers started producing a substantial mechanical hum. Classe told me that it was likely from DC on the power line. The hum was there even when the preamp was switched to standby, and even when I plugged the amps into different sockets.

My questions:

1) how much DC on the powerline does it take to cause problems with audio equipment?

2) How does DC get into the AC signal on the power line?

3) Do the power companies have any spec they need to acheive for maximum DC?

4) Or is it more likely appliances within my house causing the DC.

Thanks, Peter
peter_s
Forgot to post that @Gbart built me a very nice custom DC blocker that allowed me to not only address my transformer hum in my preamp but also use the outlet I wanted, which is one of Al Porter's Ports.

Great service and product all around. :)

Scott
gbart,
would love a dc blocker as well if you're willing:) I'm unsure how to get a email to you through the new agon system.
Thanks
Chris
Gbart,
Would you please send me an email to actusreus13@hotmail.com if possible? I'm also interested in your DC blocker, and I have another question for you as well. Thank you.
Actusreus, I sent you an e-mail message.

Chris, you can reach me by e-mail at sae_2300@optimum.net