Mackie Mixers...Help

[systmovadown]

I have a
Mackie Micro Series 1402-VLZ mixer

I have used it on recording and stuff....and when I do, I get this loud EHHHHRRRR sound...
its so annoying
arent mackie mixers known for super quiet?

I thought at first it was the cable that went frmo the mixer to my computer, but it wasn't.
It's not the card either. I hooked the mixer up my P.A system and it has the same noise...

Please help me

If I take it to Guitar Center, would they help fix my problem?
-Thanks

 

[Cloneboy Studio]

Are you using balanced inputs and outputs and have a power conditioner that the mixer is running off of? Is probably dirty power causing AC hum and ground loops.

 

[systmovadown]

Are you using balanced inputs and outputs and have a power conditioner that the mixer is running off of? Is probably dirty power causing AC hum and ground loops.

dirty power??
balanced inputs and outs yes....
dont have a power conditioner that the mixer is running off of....
should i get one?