Electronics > Projects, Designs, and Technical Stuff
Shielded against 60Hz speaker cable
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Hextejas:

--- Quote from: Cliff Matthews on March 16, 2019, 01:00:42 pm ---Looks like you're getting closer to solve this.. So we see the offending speaker cable runs from an amp with its own power supply is running parallel with the other speaker cables. It may be that amps power supply is floating and the other channels amp and the sub-w's amp are at the same ground potential. Time to breakout a DMM and measure grounding disparity.

--- End quote ---

Cliff, thank you. I would love to do this if I knew how. I am new to this electronic "stuff" and it's mostly a mystery. Can you explain in simple terms how to do this ? I will be forever in your debt.
Cliff Matthews:
You must have a volt-meter, since you've already rebuilt the amp 4 times?
1) Power-on both amps (minimum volume and nothing connected to inputs) measure and report DC and AC differences between both amps output terminals.
2) Report any DC voltage present (however small) at the output terminals on each amp.
3) Power-off both amps, disconnect from mains and wait a few minutes for amp PSU caps to discharge. Report resistance between positive and negative output terminals to chassis ground on each amp.
4) Still disconnected from mains, report resistance from the chassis of each amp to its wall plug connector (to see if open).

There may be other checks others may want to add, but these are just a few.
coromonadalix:
you can short your amp input at 0 ohms  and see and follow your hum in the circuits ...    the short will garanty  nothing enter or no antenna effects / noise picking, or defective signal input cables.

Even saw long time ago, bad grounding for the frame screws to a ground tab/log  on pcb's, even checked main ac sockets for proper wiring ...


What is the amp model ??
DimitriP:

--- Quote ---I think that it has to do with the position of the speaker cable.
--- End quote ---

Did you end up removing temporarily or routing the speaker wires away from the UPS?
Hextejas:

--- Quote from: DimitriP on March 16, 2019, 06:41:15 pm ---
--- Quote ---I think that it has to do with the position of the speaker cable.
--- End quote ---

Did you end up removing temporarily or routing the speaker wires away from the UPS?

--- End quote ---

I did this partially which I think helped the left speaker.  The amps and power supply are on a mains circuit by themselves. The left speaker is free of hum. But there is a UPS in the path of the right speaker so I will try removing it entirely.

Separate question. The UPS has a heavy battery in it. Can the battery contribute to the hum problem ?

The sub woofer I think, is part of the problem. It is located near the right speaker with its own power cord plugged into a separate wall receptacle. For a short length, the right speaker cable parallels the sub woofer power cord.
I am gonna take the sub woofer out of the chain and see what happens. I will post my findings later.

I really appreciate all this excellent help.
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