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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
ja_kub_sz's avatar
ja_kub_sz
273 posts
 
Funny, I was using my sub's Line Input/LFE connection via RCA cable from my loop out right/left connections on my power amplifier and all was well.

Now using the high level speaker input connection with the amps plug adaptor off my speaker terminals and I get the 60Hz hum.

Need to mess around with it more, but why would the power amp to the LFE be fine, but not the high level speaker terminals (producing hum)?
dgluke
100 posts
 
Have not read all responses. So at the risk of repeating, the most common cause for a subwoofer hum is cheap cable or a cheap cable that eventually went bad. Poor shielding is the most common exact culprit on a cheap cable. Power cord is also a possible culprit. Solid copper 75 ohm Quad Shield RG6 terminated with a RCA plug is an inexpensive alternative to all the other types of subwoofer cables that are offered, sold or recommended as being the best. None of those offerings will be quad shielded. The solid copper coax RG6 cables are easily found and are probably the least expensive of all the options.   
noromance's avatar
noromance
9,811 posts
 
nob and tube
Knob and tube. Cost me a fortune to replace after some flood damage.
spacecadet65's avatar
spacecadet65 OP
58 posts
 
OK. So I was wrong about one thing. The permanently attached power cable is a 2-prong, polarized version, where you can't invert it in the wall socket. So there was no way to use a cheater plug to get out of this. 

@jea48: It is definitely the middle YouTube video hum. Great videos, BTW.

This is a pretty old unit. $400 gets me a basic 12" Emotiva sub that will run rings around it. I may open it up and take a look at the caps. If it looks like there's something obviously amiss, maybe I'll try to do a repair. It's not worth paying someone to work on it given what it is...

I really appreciate all of the advice!
erik_squires
16,118 posts
 
Hey,

If you get the hum with NO audio connections and just plugged in you need to have it serviced. It’s probably a power cap that’s going. Get them all replaced before it blows.  If you can afford it and they are available, get higher temp caps than you originally had.  They'll have a much longer lifespan.

Best,

E
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