I have recently brought a new PA amplifier and new cables as my old amplifier took RCA and this new one takes XLR, so when my new amplifier arrived I set it up like normal and realised there is a strange noise conning out of my speakers: a high pitch noise and a humming.

I have looked up on the internet and found it to be sound interference. It is very annoying sound, but when the music is playing and I turn the volume up I don't hear it - but when the music is on mute you can hear the noise loud and clear.

My amplifier gets signal from my PC which is sent to my equalizer and then to my amplifier and both my equalizer and amp are fine as I have tested them. It is either the wire from my PC to equalizer that is the problem or my XLR from equalizer to amp wire that is the problem.

Where is the noise coming from?

  • Is the noise still there if you pull out the plug from the computer? (i.e. only the EQ, Amp and speakers should be connected - pull out the plug in the EQ, not the computer). Commented Oct 12, 2015 at 7:12
  • What type of cable do you use from computer to EQ? What model is your sound adapter? Commented Oct 12, 2015 at 7:13

3 Answers 3


If you have replaced your speaker cables, the new cables may not be shielded cables,or those with a poor quality shield if they are. Cheaper budget cables that have no or poor shielding will act like an antenna and pick up RF or radio frequency signals which are then amplified by the amp or pre-amps in your mixer. They could be picking up the sound of a poor electrical grounding at the home if this is a low frequency hum, they are also known to pick up other electrical appliances like a fridge motor hum, high voltage air conditioning etc to name a few, or even radio frequency noise form neighbours, high voltage power lines etc. Higher quality shielded cables, both speaker and instrument / mic cables help prevent this from happening as the shielding is of a higher grade & quality than those of a lower grade, which basically use a prouct very much like a cheap aluminuim foil shielding. I would check the cables first then is it is not this then try a process of elimination, like trying it setup in another environment (ie friends house) if you think it may be poor grounding at the premises. - Hope this helps - S.


Have you considered using a power conditioner? Check out my answer here for an explanation: Fix for terrible "Hard Drive Noise" Audio Interference?


Polarity my brotha. Sounds like to me at least. Get you a ground drop adapter [3 prong -> 2 prong] and flip it to reverse the polarity. Give it a go on the amp power chord first. If that didn't fix the noise on mute, then>

Go channel by channel and see if maybe it's only a single/group of channels or possibly a cable.

Chances are, it's the power source or a cable.

Steer clear of "power conditioners" unless you plan on buying a real one. If the individual outlets/transformers aren't isolated, or there is only one transformer in the entire unit, then all the outlets suck if one sucks.

Oh, invest in an outlet tester. The majority of outlets provided for bands are almost always bad.

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