Networking & wireless forum: A/C amplifier with wireless microphone

You mentioned an AC amplifier. Can you tell make and model? You said the sound is low pitched. Are you sure it's feedback and not 60 cycle hum? Such hum is insidious and can have many causes. Poor grounding, bad connections, unshielded wiring, impedance mismatched devices etc.

Very near the location of the building where the noise happens is a city water treatment plant. At times there is no problem until the end of the 2 hr. session. Is it possible that when the motor of the treatment plant kicks on, it sends out sound waves? Just snatching at straws here.

If the noise is present, but the receiver (mic) is not being used, could the receiver still be a problem? Obviously, this is not my device, just trying to help out a friend. Wouldn't the receiver have to be turned on before it could facilitate interference?

Never thought about having the friend try using the amplifier on batteries. Good idea.

The noise has appeared after a couple of hours or right from the beginning. Usually when I've heard a noise which involved a receiver, it is very high pitched, as I have sensitive ears when it comes to high pitches, but the noise is more like a very loud lower mono tone without the high pitch.

Then it does sound more like an impedance or outside interference issue. I could suggest trying what's called a "Faraday cage" but this seems like trouble. The connecting cable from receiver to amp could also be an issue. The cheaper ones are worse. As well, the longer the cable, the more vulnerable they are to acting like antennas. You'd really need to play around with several ideas when the noise was there in order to get a good grip on what was causing it and how to address it. Good luck with it.

ground path so your tinfoil cover may need one too. When you wrap your palms around the phone, you're actually shunting some signal to earth through your feet even if wearing shoes. If you find that you can make the tinfoil shield work, you can look for something less tacky in appearance. Good luck again.