Mic interference stops when PC plug taken out! Why?!

M

musicdavid

Member
I am getting a horrible hissing interference from my mic (SM57) and I have discovered that it stops as soon as I pull the plug of my PC out of the socket (I'm checking the mic by listening to it straight through my mixer's headphone socket).

It's annoying because I use the PC to run my recording software so as it stands, I can't use the mic in my home set-up.

Could it be an earthing issue? The plug sockets being overloaded? I'm no electrician!

I find it strange that it only seems to happen with this mic, although I have had noise interference problems before from a keyboard (albeit on a different PC).
 
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We'd need more info about your setup, but the first thing that comes to mind is a ground loop.

Is it a low freq hum sound you're hearing?

If you have more than one powered appliance in your setup, make sure they're all powered from the same outlet.
 
Steenamaroo said:
We'd need more info about your setup, but the first thing that comes to mind is a ground loop.

Is it a low freq hum sound you're hearing?

If you have more than one powered appliance in your setup, make sure they're all powered from the same outlet.
Click to expand...

It's more of a buzzing, actually.

The PC, Mackie mixer and Yamaha 4-track are all being powered from the same socket.

Interestingly, I've just taken the 4-track* out of the chain and this also seems to cure it (even with the PC plug in). Still strange that it should only affect this mic though and not my other one.

*I was using my 4-track as it seemed to give the mic a boost. I only get the volume boost from the mixer if I engage the 'pre-fader solo' button.
 
Still need more info about your setup, but perhaps there's a mismatch between balanced/unbalanced signals, or between signal levels.

Describe your path. Eg.

Mic -Xlr to xlr cable - mixer xlr input - main output - TRS to TRS cable - 4track line input etc.
 
What's you other mic? Dynamic mics need maybe 20dB more at the pre than condenser mics, so maybe you are getting it on you other mic, but it's a lot quieter.

Also, I've seen mics used with XLR to unbalanced jack leads, if you are using one of these it's going to be very interference prone. Some Yamaha 4tracks use an unbalanced jack input for mic, so this isn't as unlikely as it sounds.
 
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