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Whooshing sound from mic, but only with mixer and not with USB interface

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Whooshing sound from mic, but only with mixer and not with USB interface

Postby athosar » Mon Jun 29, 2020 6:17 am

Hey everyone, I'm having a very weird problem, at least nothing I've encountered before granted I'm not the most experienced. I have a Rode NT1-A, a Mackie ProFX12(v2) and a Behringer UMC204HD interface.

When I plug the mic into my Mackie mixer, there is a very loud whoosing sound that increases with gain, this is present in phones output as well as in recordings through USB. I've tried switching cables, locations, power sources (properly grounded outlets) and all other variables I could think of and it just won't go away. My friend has an NT1 which is perfectly quiet when plugged into the mixer, as are my dynamic mics but this one makes the sound.

I was curious as to whether it was the mixer and I think it is because I plugged into my Behringer USB audio interface and the mic is silent and records great. There is no sound in the phones output either. I tried muting all other channels in the mixer, making sure effects and everything else other than the mic was turned off, tried different channels for the mic, but the sound is still present.

Any ideas or solutions? Thanks in advance!
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby Tim Gillett » Mon Jun 29, 2020 8:16 am

You did say your friend's NT1 works but have you checked phantom power is switched on?
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby blinddrew » Mon Jun 29, 2020 8:56 am

Does it happen on all the channels of the Mackie?
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby Hugh Robjohns » Mon Jun 29, 2020 11:17 am

Given your descriptions I'd say they point towards a problem with phantom power in the Mackie mixer and/or a microphone which is unusually fussy about its phantom power supply voltage.

So, as Tim says, check the phantom power switch in the mixer is on as a first step. I doubt it will change anything, but it would be worth checking whether you have the same problem in other mixer mic channels as Drew suggests. It might also be worthwhile temporarily disconnecting any other XLR cables plugged into the mixer input channels, just in case something else is dragging the phantom supply down.

Do you have access to a multimeter to check the phantom voltage?
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby Stickman0_3 » Mon Jun 29, 2020 1:08 pm

If all else fails, you may need to plug the mic into a graphic equalizer and try to pinpoint the frequencies to cancel them out. Just a thought.
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby athosar » Mon Jun 29, 2020 3:27 pm

Tim Gillett wrote:You did say your friend's NT1 works but have you checked phantom power is switched on?

Yep phantom power is switched on this while time!
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby athosar » Mon Jun 29, 2020 3:29 pm

blinddrew wrote:Does it happen on all the channels of the Mackie?

Yeah, I mentioned that in the post above as well, I unplugged everything but the mic and tried every single channel individually but it whooses on all of them.
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby athosar » Mon Jun 29, 2020 3:30 pm

Hugh Robjohns wrote:Given your descriptions I'd say they point towards a problem with phantom power in the Mackie mixer and/or a microphone which is unusually fussy about its phantom power supply voltage.

So, as Tim says, check the phantom power switch in the mixer is on as a first step. I doubt it will change anything, but it would be worth checking whether you have the same problem in other mixer mic channels as Drew suggests. It might also be worthwhile temporarily disconnecting any other XLR cables plugged into the mixer input channels, just in case something else is dragging the phantom supply down.

Do you have access to a multimeter to check the phantom voltage?

The phantom power switch has been on this whole time, that's the only way my friends NT-1 worked as well. I do have a multimeter though, how would I check the phantom voltage??
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Re: Whooshing sound from mic, but only with mixer and not with USB interface

Postby Hugh Robjohns » Mon Jun 29, 2020 4:32 pm

athosar wrote:I do have a multimeter though, how would I check the phantom voltage??

Excellent!

Set your meter to a 50V DC scale -- or higher -- (if it needs setting).

With nothing else plugged into the mixer's inputs, and phantom power switched on, push the meter's black probe into the pin 1 hole of one of the channel input XLR sockets.

The pin numbers should be embossed on the plastic insert, but if not pin 1 is the hole on the top right when the three holes look like a face!
Image

Push the red probe into the pin 2 hole which is the top left.

If your probes won't fit into the holes, find an XLR cable with connectors that can be easily undone -- Neutrik are the easiest -- and access the pins from inside the XLR connector instead. Pin 1 has the cable screen on it. (Leave the other end of the XLR cable unconnected to anything.

You should see something between 44 and 52V DC on the meter measuring between pin 1 and pin 2. You should get exactly the same reading between pin 1 and pin 3 (the middle bottom one).

If that's all fine, then connect an XLR cable between the mixer and the troublesome mic, and open up the XLR connector at one end of cable -- it doesn't really matter which.

With the mic connected now, measure the voltages between pin 1 and pin 2 and between pin 1 and pin 3. You should see something higher than 9.5V DC -- hopefully a lot higher!

When you have those figures report back. They might possibly indicate a problem. Hopefully they'll all be within spec... and we'll have to think again!
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