Ground Hum Day? (audio)

Can any of you lads tell me wtf might be making this sound?

Noise

Every time I arm an audio track in Logic, I get this background noise. I'm running my Kurz PC3 into a bus-powered PreSonus Firebox. Kurz, Mac Pro, screen, monitors, and a small lamp are all plugged into a nice grounded multi-plug thing.

FWIW, I have to really crank the gain on the Firebox to get a good signal (volume on the Kurz is at max). Is the Firebox to blame? Should I use something that's not bus-powered?

Thanks, all.

Oh man. Where to start.....

First off, I know of one half-million dollar studio that has hum issues because the contractors that built the place and did the electrical work cut corners.

Start with your electrical mains. You should have your audio gear on a separate breaker from anything non-audio related. That includes lamps, printers, etc. Generally speaking, PCs can be on the same breaker as audio gear, as long as they are not connected directly to cable TV via a TV tuner device.

Good quality power strips, surge protectors, UPSes, and voltage regulators/conditioners are necessary. If you can't afford something like a Furman AR-1215, then go at the very least with a set of decent power strips that have EMI filtering.

Then comes your audio cabling. Good quality cables make all the difference. Read up on the difference between balanced and unbalanced signals.

Probably you are now realizing something that a lot of people don't realize when they buy synthesizers....Which is the hidden cost of being able to use them for recording.

It's all well and good to plug in some headphones. But if you want good quality recording capability, you gotta shell out dough and time to make it happen.

You are talking about USB, right?

I've used a PCI card for many years without any problems.

Then just a few days ago I bought a USB audio interface (Novation NIO) just to try it out. I'm getting the same thing you are. The audio interface sounds fine (no hum) when I am playing audio just from Windows XP, like Windows Media Player. But when I open Cubase SX, I get the hum.

The hum changes volume if I plug my self-powered speakers into a different wall outlet - but no matter what I try, different power strips and UPS boxes, it never goes away completely. So it IS caused by a ground loop it would seem. Anyway, I'm going back to PCI.

are you guys using laptops? mine works fine when it is running on battery power but as soon as i plug it in the hum returns. i dont remember all the technical mumbo jumbo as to why this happens but it seems to be common with some brands/chipsets/whatever.

im sure someone who knows what they are talking about could elaborate