Sunfire MK II help?

Question

Sunfire MK II Hums on input signal. Hum can be canceled repeatedly by switching on or off lights in room. Problem is consistent. Sometimes a small electric shock can be felt at a light switch. Is this a grounding problem? How important is a proper ground?

Answer 1

Yes, this is typically referred to as a 'ground hum'.  You're hearing the frequency of the electricity.

What you can try to do is reconnect all your equipment to see if you can isolate what connection is picking up the hum, then either change the cable out for a 'ground loop isolator' version of that cable, or change to a optical cable which is immune to ground hum.

A small shock felt at the light switch sounds like static discharge.  All electrical recepticals are grounded.

If your electrical was done by a reputable electrician (not a do-it-yourselfer or general contractor) then you can pretty much assure yourself that the problem isn't the electricity, it's ground hum from poorly designed equipment.

However, if you have any doubt about the safety your home, I'd have a electrical inspector come over and check your wiring for any problems.  This is a small cost to ensure you're home doesn't burn to the ground.

But the symptoms you describe are not unusual in any way, it's just going to be a chore to go through all the discovery to find the problem equipment or cable in your setup.