AC Hum problems

[chrismuktar]

Hi all,

I have a problem with AC Hum. I am connecting a Presonus Firepod's Main CR Output (Jack output) directly to a Tannoy Reveal Active Monitor using a balanced cable (Jack-XLR).

I'm experiencing AC hum from the firepod. The firepod is an ungrounded device, and is powered by an external power supply. I've been testing this with nothing else attached to the firepod (including the computer).

With both devices powered of the same supply, the tannoy does not make any hum until the firepod is connected to it.

I have been using the Tannoy's successfully for a long time using a Tascam US-122, which caused no hum whatsoever.

My last guess is the branded presonus power supply, but I find it hard to believe that they would provide an inadequete supply to a pro audio product.

Any ideas?

Much appreciated,
Chris

[C00kie]

Either the ground on (one of) the power cable must be lifted, or you could try an unbalanced audio cable.

Are you absolutely sure the connection with mains power is not grounded? Otherwise you cannot get a ground loop.

[ross g]

is this a new problem from existing equipment or a problem with new equipment? no matter the brand, stuff can go wrong, a soldier can break, a lead work loose, etc... a bit more sequence of events might help with diagnosis..


rg