Remove Buzzing on PC Line In Jack with Audio Compressor After Mixer

Question

I have done some pretty detailed trouble shooting on this and just want to know what additional equipment or things to try to eliminate the electronic buzzing noise I get.

• PC Line In Jack
• Behringer Xenyx802 8 channel Mixer
• Behringer MDX4600 Audio Compressor/Limiter

If I connect ONLY the mixer to line in jack no interference is heard and recording audio sounds just fine.

Connecting ONLY the compressor to the line in jack with the POWER OFF and the power plug connected in any socket or surge protector... the buzzing/chirping noise is heard when 'listening' to line in input on my USB headphones.

If I connect the same compressor and/or mixer with the power ON or OFF, but to a DIFFERENT computer... there is no problems and recording audio sounds just fine with the compressor doing it's thing.

So I am left with feeling it is something unique to the computer I want to connect to, which has nothing out of the ordinary and is a brand new PC. It uses the onboard motherboard audio jack with the same audio driver as the other PC.

Any ideas? I am not sure if since it is obviously something to do with the power or grounding connection, if a line power filter or something would help.

Answer 1

The internal sound card of the computer is most likely the problem. These onboard audio components are very cheaply made, meaning they are not designed to avoid interference from other components and power lines inside the computer and they also don't have the filtering to remove interference once it enters the audio path.

Get an external audio interface: usb / firewire or dedicated breakout cable.

I've had the issue a number of times with desktop PCs and laptops, and replacing the audio interface was the solution each time. Be sure to buy an audio interface from a place that allows you to return it after testing though, because I've also encountered the occasional (cheaper) external audio interface that has a shielding/interference/ground loop problem causing noises.

Answer 2

EMV is very much correct but there are a number of things you can do to reduce the hum.

Make sure all of the audio equipment is on the same circuit to help reduce chance that you are in a ground loop.

Add a ferite clip to the analog audio cable.

Change the surge protector that you are using. Different pieces of equipment can be more sensitive to cheap surge protectors.