60 Hz Hum from Powered Sub

oldhvymec

... A common and a ground CAN (not should) share the same bus with a jumper in the main. I keep them separate. That jumper can be the source of a lot of noise in house wiring ...

It isn't clear what you're saying here. All neutrals and grounds must be bonded together at the main panel - and only at the main panel - for safety. That is very a basic NEC requirement. No exceptions.

Thanks cleeds I got a phone call from a city official I been waiting on.. I got excited, only took a month for the call back. :-)

Excuse me, I meant to say sub panel, and must be bonded at the main.

At the a sub a jumper can be between the TWO. It will work but I separate and have found it to be a source of noise in my house wiring.

I check ground and commons for amperage to ground. It always amazes me what I find there and the difference between the TWO.

A 220/240 sub panel, with a blower motor using L1 and L2 and in the same sub panel, stereo receptacle (s) being uses on one or the other hot rails. That is a no no in my system for noise..

My house is quiet and I have a  mix of nob and tube on the old AND Romex on all the new construction.  SOOW 4/3/g feed both shops, and 12/2/g for all shops, basement, kitchen and attic outlets..

The house is 14/2/g and nob and tube.

Bottom line OP shared grounds can make noise..:-)

@ spacecadet65,

Which sound best describes the hum you hear from the sub?  

60Hz hum  
  https://www.youtube.com/watch?v=SVZ2P0KsLic     

60Hz buzz  
https://www.youtube.com/watch?v=FBRPHojSGAs

120Hz hum  
  https://www.youtube.com/watch?v=pC4Uzt0qm2E


Did you try a 3 wire to 2 wire cheater plug yet?  
Make sure you insulate the ground tab on the cheater so it does not contact the 6/32 trim screw that holds on the outlet cover plate. The 6/32 screw is grounded.

Almost all subs have a "plate amp" with a switching power supply and are very prone to this type of problem. Check with Tannoy and see if they have an exchange program where they send you a rebuilt plate amp, which you can change out yourself. If not, some repair shops will work on the removed plate amp, saving a lot of shipping cost. Also if you remove it, sometimes it is easy to spot a split cap.

Are you using the low or high level inputs to the sub? If you're using the low, it's probably a bad cap in the subwoofer. You might just try the high level inputs if you have them. I know that cured the hum in my older Sunfire sub years ago. I replaced all big electrolytic caps and it still hummed, no matter what I did. This just might work? It would be a temporary cure until you either upgrade to a newer and better sub, or decide to send it in for repair. Good luck.