Weird "heartbeat" noise with Shure SM58s!

[FloydBenson]

Hi everyone, I'm running Cubase SX and I've got a strange problem.

I have a couple of Shure SM58s and I use an Edirol UA-25 audio interface.

When I try to record with either of the SM58s, Cubase records onto the track this strange regular 'pulse' sound that closely resembles a heartbeat, indeed the waveform looks like a medical AKG report!

This only happens when I acually press the record button, and does not happen with line instruments or even a crappy cheapo mic I tried.

I've tested both the SM58s in Sound Forge, and they work fine, clear as crystal.

I'd be very grateful if someone could post a suggestion, is there perhaps some known non compatibility issue with Cubase and Shure SM58s?

Thanks a lot

Lyle

[TripleJ]

That's quite bizarre. Theres obviously no compatability issues seeing as how it's just a voltage running through your interface. There's no identifier or anything.

[boogle]

There is something else, what you described is not possible. If the noise is regular than that almost guarantees that the problem is digital, I would suspect the interface.

Is the sound noise or is it crackling. (If you put a frequency analyzer on the noise does it look like it is pretty much all frequencies or is it a peak in just one frequency band?

[FloydBenson]

It really does sound like a heartbeat, it's not crackly or poppy.

Here's a screenshot of the audio with the mic plugged in http://www.flickr.com/photos/8340238@N08/496388421/

and here's one with the mic unplugged, but the cable still plugged in
http://www.flickr.com/photos/8340238@N08/496388425/

On the on without the mic plugged in you can still see little pulses, so Im presuming it's a problem with the cable and have ordered a new one.

I just don't understand why I dont get this when I record on Sound Forge with the same mics and cable.

The interface is fine with other mics or line instruments too, it can't be a fault with that.

[boogle]

I am not so sure that is a cable issue, looks to regular. Can you record about 20 sec. and post it somewhere where I can hear it?

And if you do keep it in .wav or something, I do not need it streamed, just to be able to download it.

[Bass Jas]

What other programs are running in the background?
I see in your picture you have firefox running and you are
browsing this forum which auto updates every few seconds?
Just a thought, and do you have any antivirus programs running?

What other devices are plugged into the same outlet or circuit?