Recoding 'noise'

Sorry if this has been asked before (I did do a search).
But, I’m attempting to record of my DJ mixer into audacity 1.3.10, the issue is however that there is a lot of background noise even if i hit the recording button without even playing any music.
I have it set up in such a way that i have attached my dj- mixer into a preamp, through the digital output connection. This is then connected too an external audio interface which is connected into a USB drive on the computer.
I have tried adjusting the gain on the preamp and recording levels within the computer, but the extra ‘noise’ seems to increase and decrease proportionally with any level changes, making me have a quiet recording with a little bit of noise or a loud recording with a lot of noise (neither is worth listening too), any advice would be greatly appreciated.

Do you still get noise if you completely disconnect the DJ mixer from the USB interface?

After disconnecting the DJ mixer, the sound is pretty much gone, i’m not sure what conclusion i can draw from this though, as i’m not entirely sure how to fix the output on the mixer.

Could you be more specific about exactly what devices (make and model) are connected in the chain and how they are connected (analog, S/PDIF, USB, etc)? I can’t understand why you need to go through the “pre-amp”.

– Bill

Thanks for the time you guys spent helping me out, i think ive found the problem to be the use of the digital output instead of the tape output on the back of my mixer. When swapping to the tape output, the signal is coming in perfectly.