Strange noise caused by phantom power on a M-audio Luna : some ideas on the matter?

Q

qandre

New member
Hi all !

(I first posted this in the "Recording techniques" forum but it might not have been the best place...)

I recently bought a second-hand mic M-audio Luna, and just performed the first tests with it. And a strange noise is annoying me... I have a M-audio fast track pre-amp and record on Garage-band on my 13'' MacBook Pro.

I have recorded the noise for you to listen. In the first half, it is very strong because I touch the stand, shockmount and XLR cable alternatively, and this actually enhances the noise (what do you think of that by the way?). In the second half, you can hear the high pitch noise when the stand etc are left still.

The gain was 50% but does not affect the strength of the noise. +6dB was added in mixing.

Do you think it is due to the mic? Or the pre-amp?

Thanks in advance!

Quentin
 

Attachments

  • test mic.mp3
    821.3 KB · Views: 49
If the noise changes when you touch this or that then you have a ground problem. Bad connection somewhere. But this doesn't sound like a bad ground. It sounds like feedback. Do you have the mic close to your monitors?
 
Thanks for your answer.

Well yes the mic is quite close to my monitors, but my monitors are always off during recording...
 
Interesting fact!

The noise isn't there when my recording software (GarageBand on my Mac) isn't on...

What do you think of that?

Thanks!
 
I have never heard a "noise" problem sound like this. This sounds like a cable hanging over a keyboard hitting a key. Do you have other inputs armed at the same time?
 
I have no other inputs... And the strangest thing is that the noise is not there when I am just playing, it appears as soon as I launch GarageBand..!

It is true that I have a long XLR cable (10m) but it is top quality so I can't believe it is responsible of this neither...

I am at least as puzzled as you are!

If you have some other ideas, I would be glad to hear them!

Thanks :)
 
That is classic data bus noise - used to be quite common with poorly designed internal sound cards. Sadly, on an external audio interface, it's likely to be a fault - although sometimes it's caused by a grounding issue, or even just a poorly screened usb cable from interface to computer allowing the data stream to be induced back into the audio analogue side. Touching the mic or stand alters the tone of the interference by allowing the body to couple more interference back into the audio circuitry. Worth experimenting with some extra grounds - but more likely to be something simple inside the interface like dry joints.
 
rob aylestone said:
That is classic data bus noise - used to be quite common with poorly designed internal sound cards. Sadly, on an external audio interface, it's likely to be a fault - although sometimes it's caused by a grounding issue, or even just a poorly screened usb cable from interface to computer allowing the data stream to be induced back into the audio analogue side. Touching the mic or stand alters the tone of the interference by allowing the body to couple more interference back into the audio circuitry. Worth experimenting with some extra grounds - but more likely to be something simple inside the interface like dry joints.
Click to expand...

Thank you so much for your answer!!! A new USB cable actually did the trick, you are a saver :)

Being here, I would like to ask you one more question, please. I have some ground issue in top of that. An annoying buzz, with a strong component around 50Hz. Approaching my hand of the body of the mic enhances the buzz (I am some kind of antenna right?), and putting both hand in different places on stand, mic or shockmount eventually suppress it...

How could I solve this problem or at least reduce the buzz significantly? Unfortunately a high-pass filter is far from enough!

Thanks again!

Quentin
 
You must log in or register to reply here.
Back
Top