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Intermittent Noise in Studio, Possible Interference Multi-Channel Preamps
Old 13th June 2018
  #1
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Thread Starter
Intermittent Noise in Studio, Possible Interference

Hello everyone, I've posted my issue in the basic troubleshooting thread to no avail.

In the studio I work we've been running into some noise issues, specifically with microphones. It's a crackling sound that is present with or without a signal, but it seems more present when there is a signal. Here's the system:

24 Channel input box at live room

1x Midas XL48 (Inputs 1 - 8)

2x Audient ASP880 (Inputs 9 - 24)

Mackie D8B Mixing Console

MOTU 2408 Mk3 Converter

Black Lion Audio Microclock Mk3 (acting as Master Clock for digital devices)

Mac Pro

1x Furman Power Conditioner

1x Monster Power Conditioner

Everything, even the Furman, is plugged into the monster power conditioner. Previously everything was plugged into 4 outlets in the wall at the same box, then I consolidated it all to eliminate a ground loop as the issue, but there was no change.

I attempted some basic troubleshooting, and the only conclusion I could draw was that is happens only when phantom power is engaged. I cycled through a few mics and cables and it was still there, and it happens across all 3 preamps. What's odd is that during testing the SM7B (with no other mics plugged in) produced no noise, but in a session the noise was present on the channel recording the very same microphone (although there were other channels running too, including mics with phantom on).

Audio clips from said session:

Noise Sample (All Tracks)

Noise Sample SM7B (Gain Boosted)

Noise Sample KM184 Pair (Gain Boosted)

The tracks are unprocessed, so the noise is pretty quiet but it's there!

On the KM184 track, you can hear how the voice in the background gets muffled and distorted by the noise. In the final mix (during a quiet section) you can hear the noise and it had an audible effect on the cymbals, as these were used as drum overheads.

Any tips or suggestions are greatly appreciated!
Old 13th June 2018
  #2
Gear Addict
Well you have a lot of gear on the go there. It'll be hard to troubleshoot if you keep it all plugged in.

i would approach this by starting with as simple a setup as you can and see if the noise is still present. Hopefully it won't be and you can start adding gear.

And by simple I mean actually unplugging connecting cables and AC power to devices.
Old 14th June 2018
  #3
+1 to the advice of starting simple.

You have too many variables.

Start with an interface and a mic plugged straight in to it from the control room.

Then add more items. Maybe leave the snake to the live room for last.

You don’t say if its just microphones or if guitars and other input sources have the same issue?

What about moving the gear around physically or rotating it? Maybe try taking a transistor radio into the rooms and see can you get the same noise between stations on the AM band? Make sure it is a battery operated radio.

Best of luck finding the source!
Old 14th June 2018
  #4
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Thread Starter
Thanks for the input! Yes, I should have mentioned it's only microphone sources that are picking up the interference. I'll start as simple as I can! Maybe I can start with bypassing the mixer and going straight from the preamp into the interface and see what happens.
Old 14th June 2018
  #5
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andersmv's Avatar
 

That's odd. Try taking the Black Lion clock out of the chain.
Old 14th June 2018
  #6
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Thread Starter
I'll give that a whirl too. What should I use as the master clock instead? Or should I let everything go off its own clock and see what happens?
Old 14th June 2018
  #7
Quote:
Originally Posted by geoffreyweber89 View Post
I'll give that a whirl too. What should I use as the master clock instead? Or should I let everything go off its own clock and see what happens?
Yes, take the clock out. Let each item use its internal clock for this test.
Old 15th June 2018
  #8
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Thread Starter
I unplugged the BLA clock and set the interface and mixer to use internal clocking, but now I don't get playback from Studio One. Forgive my ignorance, I didn't set this system up and am still familiarizing myself with the exact signal flow.
Old 15th June 2018
  #9
Here for the gear
 

Thread Starter
Since I couldn't get playback without the clocks set internally, I used the 2408 as the master clock for the mixer. The noise was still there, no change in volume or anything.
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