in board hum, can someone help me?

[theatretechie19]

i have a Crest Audio HP8-32. there was a nasty low freq hum coming thru the mains. i muted the Groups and it went away, but wen i mute all of the channels themselves, the hum is still there. the board is only i 2 months old, anyone have any ideas where the hum is coming from?

 

[3dB]

i have a Crest Audio HP8-32. there was a nasty low freq hum coming thru the mains. i muted the Groups and it went away, but wen i mute all of the channels themselves, the hum is still there. the board is only i 2 months old, anyone have any ideas where the hum is coming from?

If you are using redundant AC connections (connecting the Console to AC via the console's internal power supply and an outboard power supply simultaneously) - you may have developed a ground loop between the two AC sources. If this is the case, and you want to continue using the dual AC setup - the console has a "Ground Linking" barrier strip on the back which has a metal linkage tying the audio ground to the console's chassis ground. Removing this linkage may help your audio output hum problem.

These concerns are addressed in the "power supply" section of the console manual which will also cover several other options concerning AC connections. If you don't have a manual, Crest should have a manual in PDF form on their website.

Regards,
Mark