Ground hum or broken condenser mic?

[Cezband]

Just moved house, so I've packed away all my stuff and now set it all up again. When my condenser mic is plugged in, there's a consistent deep hum, which whilst not unbearably loud is still a huge pain in the ass. The sound quality is fine other than the hum.

Wondering if someone can recommend a good checking strategy for my set-up to see if it's a ground loop or if my mic has gotten busted in transit. Essentially, my set-up is laptop plugged into mains power supply, bus-powered interface (saffire 6 usb), phantom powered condenser.

The obvious thing is to plug my mic in somewhere else and see how it sounds, but sadly I don't know anyone else with a phantom power interface. I don't get any hum from guitars or non-phantom mics, but again this is my only phantom-powered mic so I can't try out a different one and see if the hum is still there.

Maybe I'm missing a really obvious way of finding out the source of the hum. Any ideas?

[swishniak]

first thing i would check is your XLR cable. you are using one, right?

[invol]

I would also check the wall outlets to make sure they are actually wired right, and that the ground is connected. You can get a good, cheap tester at most any hardware store.

http://en.wikipedia.org/wiki/Receptacle_tester

[Cezband]

Swishniak: Yeah, fist thing I tried was a different XLR but no luck. Guess that would have been too easy!

Invol: Hm, I'd probably find one of those useful whether it solves my problem or not. I'll have a look around next time I'm going past an electronics shop