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Why would a new UPS cause humming in your PA system? |
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You have a bad or weak ground, or the UPS is creating a magnetic field from the power supply in it that is being picked up and amplified by the PA system. Move them farther apart and see if the hum diminishes.
Some UPS's don't produce a clean sine wave output, causing electromagnetic interference (EMI). A distorted 60 Hz sine wave will have many harmonics that can be passed through to the PA amplifier output.
Your UPS may also have a bad filter capicitor.
Answer
I agree 100%, however, you could also try shielding your units. Try putting tin foil on the iniside of the devices. Make sure that the tin foil doesnt cause any short circuits.
ANSWER
DO NOT PUT TIN FOIL IN YOUR UPS!!! While it is true that your UPS will produce EMI, the power emitted is very limited by distance. Unless you are running the speaker wire through your UPS, and inducing the EMI energy, there will not be enough to reach your speaker coils. Placing conducting material inside electrical apparatus is nothing short of idiotic.
The more likely cause of your noise distortion comes from a UPS being a "switched mode" power supply device (if it is a small UPS) or a the Pulse Width Modulated (PWM) output devices of a larger UPS. Both of these devices cause distortion of the sine wave on the output of the UPS and, surprising to many, on the input (supply side) electrical system. More than likely the electrical system, located on the same transformer - possibly fed from the same breaker box - is carrying that distortion out to the speaker coil through the speaker system power supply. You could put a small isolation transformer feeding the power supply of the speaker system. This should work whether the UPS is feeding the speaker system or not...as long as it is inbetween the speaker system power supply and the UPS.
Once more...Do not put tin foil inside your UPS.
"When all else fails, read the instructions. When things get even worse, maybe it's time to finally read the specifications."
First answer by ID1155118941. Last edit by Rjw22. Contributor trust: 29 [recommend contributor]. Question popularity: 126 [recommend question]
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