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Amplifier hum: Does it need repair?

I have a Bel Canto Evo2 amp. Lately, I've been noticing a low level hum from my system which is intermittent in nature. Today, it seemed worse, and it didn't go away in a few minutes like before. I turned off the turntable and determined that the hum wasn't eliminated when I moved the preamp source selector to CD. It also wasn't affected by the volume control. I turned off my Supratek tube pre-amp and determined that the hum persisted. Then I unplugged the two Vandersten subs and still heard the hum. Finally, I took the power cord out of the power strip and plugged it diectly into the wall. The hum was still there. The only thing I haven't detached are the speaker cables. It almost sounds like the hum is coming from the amp and not is not coming out of the speakers, but I'm not sure about that. I really don't want to have to ship it back to the factory for a repair. What do you think?
mlkiz
rar1's avatar
rar1
1,748 posts
 
Have you tried a cheater plug (3 prongs to 2 prongs) on the Bel Canto's power cord? This would rule out/rule in a ground loop problem.

Regards, Rich
newbee
4,751 posts
 
In addition to Rich's comment, you can determine the source of the hum by disconnecting everything from the amp (when its turned off!) except for speaker cables and the speakers. Turn it on, no hum? Good. Turn it off, plug in IC's from pre amp (with all other IC's disconnected from the preamp) - same scenerio as above, til you find the source of the hum.

Also put you ear next to the amp - you might hear a 60cycle buss from the transformer. Put you ear next to the midrange/tweeter and see if you hear a hum.

Lastly, make sure your IC's are not lying parallel to power cords or power sources, transformers and the like. Make sure that you don't have stuff with transformers near your pre-amp.

In short, though its too late for this post, take your time and be methodical in your approach.
wepratt
29 posts
 
If you determine that the hum is definitely coming from the amp or pre-amp, it might very well be a DC problem. I had this happen with a receiver and it nearly drove me nuts. Tried all sorts of tests and solutions and finally bit the bullet and bought a PS audio Humbuster which solved the problem instantly.
thorman
1,262 posts
 
Also is it possibly cable t.v connection on the same line? Just a thought!
kr4's avatar
kr4
3,651 posts
 
Before I put in a dedicated line and really solved my ground loop problems (which I had been masking with a so-called ground loop interrupter), I had intermittant hum/noise directly from the eVo6 chassis when certain halogen or fluorescent lamps were used on the same power line. It usually went away with lamp recycling.

In my other house, which had better AC all along, the eVos are just fine.

In your case, it could be DC or RF-induced noise on the AC lines.

Kal
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