What am I hearing with my old ears?

So to make a long story as short as possible... I have what I believe to be hum or hiss. However I am so new to this I'm not completely sure what I am hearing in my recordings. I think it's a ground loop but that doesn't make sense to me given how I have things connected... Let me illustrate

My "studio" if you can call it that has no sound treatment and I have my PC in the room. See diagram for connections.

http://img543.imageshack.us/img543/8204/epj6.png

From what I've read I shouldn't have a ground loop under these circumstances. Am I just hearing my PC? I think my noise floor is about ~50db but I am not sure how best to measure it. Below is the spectrum plot from Audacity.

http://img32.imageshack.us/img32/2343/m4pz.png

Here's a sample of the noise. https://soundcloud.com/al-burr/roomnoise

In the end if you just tell me it's computer noise that my old ears can't hear I will believe it :) I think I may end up building some kind of isolation box for the PC but I worry about cooling with it being enclosed.

Thanks for any advice...

I don't hear a ground loop in the audio sample that you provided. It sounds like poor room acoustics and high ambient noise. How high did you have the mic cranked? There is significant low frequency content that sounds like a heater or air conditioner running in the background. If you can't eliminate that noise, you can try engaging the high pass (low cut) filter on your mic chain.

If you want to test for a ground loop with the volume cranked, turn off the live mic. The ground loop can be masked by the room noise.

You have done a great job in configuring and setting up your studio. However, when you mix digital equipment (computers) that is not designed for audio with equipment that IS designed for audio, unintended things can happen. I've seen the VGA connector between a monitor and a computer cause a ground loop in the attached mixer. It was on my own system.

What you are hearing is the room noise. What do you have in the room. How high do you have your input and put put set.

I have the same problem with my audio. Same exact hiss happening.. I would like to find a fix

Thanks Guys...that is what I suspected with regard to it mainly being room noise. Looks like I have a challenge. The room is about 11'x13' with a large double window. I have a double glass door entrance, built-in shelving to the left of the desk and a couple of wood cabinets behind where I sit at a large wooden desk. The desk has three 23" flat panel monitors on it which I am sure contribute to all the bouncing acoustics.

With regard to the 286s and the mixer gain setting...well those were pretty high. I was attempting to not have to be sitting right up on the mic. Once I turned down the gain and moved to a more appropriate mic position the sound obviously improves. However I have troubleshot this further and determined that if I just use the ATR2100 plugged in via USA I get no whine whatsoever...still get the room noise...just no whine. However any mic connected to the mixer via XLR generates the high pitched whine. You only hear it when you crank the gain in Audacity but it's there. I am considering a USB Isolator to see if they help...also am going to temporarily lift my ground on the PC and see if that help. I love a mystery...

Here's a sound clip with all mics off...
https://soundcloud.com/al-burr/hiss-and-squeal

OK I think my problem is solved. I was simply overdriving my system. I believe Mike Phillips spoke about this in something I read. My setting in Windows for my Mic properties "levels" was set to "100". I backed that down to "3".. yes "3" and then made my adjustments at the mixer and the 286s and all is now good. Can I still crank up the gain and hear the whine??? yes but it is effectively inaudible in test recordings... I can even sit back in a more relaxed position and not be hugging the mic. Yes I will have bit of room noise and I will work on that. I am just glad that after a couple days of Googling for answers I have basically solved it through a simple fix and one that didn't cost me more money :)

Happy New Year!!!

Al Quick question. Are you using a TRS cable from the DBX ---- Mixer ?

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Originally Posted by andrewzarian

Al Quick question. Are you using a TRS cable from the DBX ---- Mixer ?

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Yes Andrew...I am using a Mogami Gold balanced TRS 6' cable.