Faint buzzing coming from sound mixer output?

[Shpeckledorf]

Hey everyone!

Before I go on with my problem, here is my current setup:

Carvin FX-1644 Mixing Console (16 Channels)

DOD Graphic Equalizer

Custom Built PC

Shock mounted Sennheiser E835 Dynamic Mic

And here is how it is all plugged into eachother:

FX-1644 Mono Output (XLR) into motherboard (Mic Input)(XLR to 3.5mm cord), Sennheiser mic plugged into channel 16 of FX-1644 (Really, really, really long XLR cable connecting both of them if that helps), and finally the Graphic Equalizer Balanced in and out plugged into Effect Return D and port 6 (works great)

Alright, so I can hear the mic perfect and sound super crisp, and the quality is 1000x better than when I used a 48v Neewer power supply for the mic, because when I used that I heard loud white noise in my recordings. Literally sounded like I was recording Niagara Falls 20 from 5 feet away.

My problem is that people I am talking to and in my headphones can hear a very very faint buzzing sound, and I have researched for a while but have only found something called ground loop or whatever. I want the mic quality to be the best it can be with no weird noise.

The Sennheiser mic I'm using isn't a condenser mic, so you may think that the mic is picking up interference with something throughout the room, but when I unplugged the mic I still heard it.

One thing I have noticed in the past is when I have my guitar on and next to my other computer, the pickups on the guitar start picking up weird frequencies from the computer and you can hear a screeching sound, so I'm thinking that maybe some of my cables aren't balanced and they are picking up frequencies and sending it through the board.

The XLR to 3.5mm jack cable is junk and I got it out of an all in one mic arm kit so it could be that, or it could be the gigantic XLR cable that connects the mic and mixing board. It's at least 25 feet long.

The way I used to have it set up before I moved the board and started using it for my mic was XLR Left and Right to RCA Left and Right, and the XLR cables plugged into the left and right output while the RCA plugged into the CBL/SAT audio input on the back of my Denon Receiver, and the receiver output the signal to 2 huge KHL speakers with no buzzing sound.


Sorry for so much information, just trying to provide as much as I can the first time around.

If anyone has any solutions they would be much appreciated.

 

[americanaudiophile]

It sounds like you have a ground loop. This is caused by have two ground connections between components. One is the audio connection ground and the other AC ground.
http/web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
http/www.prosoundweb.com/article/pesky_ground_loop_problems_plaguing_you/
Another possible cause is if you have a something else like a cable box connected to the Denon receiver. If you do try disconnecting the coax input to the box. Even if you are not on that input it can still cause a constant buzz that will go away when the box is disconnected from the cable input or the audio input of the receiver.