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Maddening HUMMMM

In an attempt to get rid of a very loud speaker hum from my tube monoblocks, I've done everything I can possilbly think of, including the following;
Changed out Interconnects, the pre amp, and the speaker cables and the speakers. I've pluged each amp into a Lightspeed A/C filter, and then gotten rid of the filter and plugged directly into the wall w/o the filter. I've plugged the amps, via a 10 gauge extension cord into different wall outlets, including one dedicated outlet. Cheater plugs, then no cheater plugs, then different combos of cheater plugs or not. I disconnected the pre and had just the speakers cables to the speakers. I tired a different speaker. I've gotten up at 4 AM and turned off each circuit at the panel, then listened again. I even tried a different amp. I've lifted the cables off the carpeted floor. Using tape and assorted other devices, I've made certain that now power cords are anywhere near the ICs or speaker cables. All Components are on rack with carpet piercing spikes. NOTHING I DO ELIMINATES THE HUM.

This all started about six weeks ago when I rearranged my room and hooked up my system on the other side of the room. No hums before. Now the mega hum. This is no small noise. This is loud enough to hear in the next room. HELP ME, PLEASE, OR PUT ME OUT OF MY MISERY!!!!! Thanks for any advice you might offer. I've tried everything I can think of. Kolledog
kolledog
mmount's avatar
mmount
3 posts
 
I had this problem on a DAC and discovered that one of the ground wires on the RCA outputs had broken off. You may want to have a quick look inside and make sure all the wires at the input of your monos are still connected.

Mike
jea48
2,944 posts
 
I disconnected the pre and had just the speakers cables to the speakers
Kolledog

If I understand you correctly you had the the offending Amp completely isolated from the rest of the audio system. Just the Amp alone with nothing connected to the line input. Only the speaker was connected, and you still had the hum problem.

Sounds to me the problem is within the Amp its self. When you moved the Amp you may have caused and internal problem. Maybe nothing more than a tube just happened to go bad.
aball
1,994 posts
 
I have had Mike's experience as well. A bad RCA jack ground will cause just what you describe. I've had it happen with cables (pulling them out by the wire is a bad habit...) but a bad jack in the amp will do it too. But if you've changed amps already....hmmmmm...

keep us posted.
Arthur
ratso1
12 posts
 
if you look on the jensen transformers webpage under the white pages section, they have a pretty thorough step by step to troubleshooting ground loop hums. see if it helps if you haven't tried it yet.
rodman99999
3,557 posts
 
Also a "ground loop" will cause hum. Buy an inexpensive gounding plug(adapter) and break off the ground terminal. Plug your power purifier into that(it will float the ground), and see if it helps alleviate the problem. Some equipment reverses AC phase from others, and can cause 60 cycle hum(like your TV perhaps). Many pro sound amps have two "on" positions(one reversed phase from the other) for this very reason. I've lost count of the times I've eliminated massive hum by flipping a plug over the years(harder to do now that everything is polarized).
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