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60 Hz Hum from Powered Sub

Hi All-=

I have an older (late 90's?) Tannoy PS110 powered subwoofer. It has a 3-prong (grounded) permanently connected power cable. Over the last month it has developed a 60 Hz hum. I've plugged it in different locations in the house to rule out ground loop. The hum is present whether there is an audio source connected or not. Is it time to just move on or is this something worth repairing? Could this be something simple, and if so, how can I diagnose it? Any suggestions are appreciated!

Thanks, 

G
128x128spacecadet65
jea48
4,446 posts
 
@ 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.
oldears
386 posts
 
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.
fiesta75
1,378 posts
 
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.
cakyol's avatar
cakyol
940 posts
 
Power your sub from the mains plug which is also connected to your other devices. Basically, all the earth potentials of all the devices must be on the exact same potential. If there is even a few millivolts difference, you will get the dreaded hum. Every device must be on a STAR connection, meaning plug everything into the SAME mains outlet with the shortest possible power cables.


jea48
4,446 posts
 
spacecadet65   said:

08-30-2021 9:13am

The hum is present whether there is an audio source connected or not.

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