System Noise in Recordings

PeterWright wrote on 6/1/2002, 9:28 PM
I have a Behringer MX602a mixer connected to a Midiman DManPCI sound card.

Even with everything turned down to zero, there is a background floor noise of around -51db, which I would of course like to eliminate.

I presume it's some kind of static from the hard drives, so are there ways of eliminating or at least minimising this?

Thanks for any suggestions?

Comments

Rednroll wrote on 6/2/2002, 3:06 AM
Static from the hard drive? That's a new one, I've never heard of this before. I would guess your wiring from the Behringer to the sound card is setup wrong. You're probably going from a 3 point connector balanced output to a 2 point unbalanced connector on your input and causing some grounding issues, which will cause an excessive noise floor.
PeterWright wrote on 6/2/2002, 3:33 AM
Well, the static from hard drive was just a guess, maybe it's from a fan - somethings going on in there!

The outputs from the Behringer are stereo RCAs, as are the in/outputs on the soundcard.

I've got the "Main Out" from the mixer going to the sound card - is this ok? - there's also a tape out, which I have connevted to a VCR.

Thanks for any suggestions.
LarryP wrote on 6/2/2002, 6:30 PM
Look out for ground loops. Short answer is use balance audio when available or at a minimum power all your equipment from the same outlet or strip. Also unplug any AC cords you can live without.

The definitive source for information on this is a re-print ($15) of an AES journal article found at http://www.aes.org/publications/other.cfm. Search for "shields and grounds" a short way down the page.

Larry
PeterWright wrote on 6/2/2002, 7:28 PM
Thanks Larry - I have ordered the CD.
Rednroll wrote on 6/2/2002, 10:06 PM
Yes, it sounds like you probably have some sort of grounding issue. I would start by elliminating all devices not needed to record (ie that VCR, may be a source of grounding issues)and then see if you still have the same noise floor. If not you can start to add equipment in one at a time and see where the source of noise is being generated from. Like the previous post mentioned, making sure everything is connected to the same power outlet is a good start also. Also, it sounds like you're using unbalanced outs/ins. Unbalanced outs have a lesser signal to noise ratio compared to Balanced Out/Ins therefore, are generally more noisy. Put that on top of the Behringer is not the quietest board with noisy pre-amps and unbalance outputs, so having a -50dB noise floor is about par for your setup. I'm using a Yamaha digital mixer with Balanced Ins/outs and my noise floor is around -80 dB when recording through the Analog in/outs and everything is grounded properly.
vanblah wrote on 6/3/2002, 8:41 AM
Disconnect EVERYTHING from the soundcard and see if you still have the same noise problems. That way you can tell if it's the soundcard or some external device.