Noise/hum from a Soundcraft board - need help!

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Emile Gauthier

Freshman
Sep 5, 2017
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Hi guys, this is my first post here, thanks in advance for your help and let me know if it's not posted in the right section.

I've been using a Soundcraft EFX12 board that I really love, to record podcasts for a couple years ago.

here's my setup:
- 2 condenser mics connected to the channels with XLR cables
- Master Record out goes to my soundcard with RCA cables

When I start recording, I usually hear nothing. But after a couple minutes, there's a noise appearing whose frequency is constantly getting higher in tones.
When I turn the Phantom power off, the noise is still there but its frequency drops suddenly (a few tones down). I have tested all other inputs, and it doesn't change anything.

I live in a pretty old building, so that can be an electrical issue. But it just started appearing in the past few weeks. I didn't change my electrical setup.

Does it look familiar to you? Do you think it's an electrical issue?

Thank you!
 
Wondering if it has something to do with the rca outputs you are using? Can you test to see if you are getting a clean signal out of the XLR outputs? Also what are you using for mics?
Guessing someone on here has run into an identical issue and can help you better than I.
 
Probably with a desktop? If it's a laptop remove the power supply/ battery charger and test again.
If you have a stereo DI or signal transformers, put them in the signal lines to test whether it's gone.
Sometimes a better ground connection can solve the issue also, you can test this with a thick copper wire in parallel with the rca signal lines.
Do you get the mains supply from the same power outlet? So avoiding ground loops?
 
Hey guys! Thanks for your help!

"Wondering if it has something to do with the rca outputs you are using? Can you test to see if you are getting a clean signal out of the XLR outputs?" -> I will definitely test that... it looks like the type of setup that would create noise. For the mics, I'm using two CAD GXL3000 condenser mics with brand new digiflex cables.

"Probably with a desktop? If it's a laptop remove the power supply/ battery charger and test again." -> the noise is pre-laptop, I mean that even with the laptop disconnected, I hear the noise. Do you think it could be linked to the laptop's electrical setup?

"If you have a stereo DI or signal transformers, put them in the signal lines to test whether it's gone." -> I do have a DI, I can test that, good catch! Would you put it between mics and channels?
 
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