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Mic/pre-amp combo causing whine - what to replace/buy Condenser Microphones
Old 7th September 2011
  #1
Here for the gear
 

Mic/pre-amp combo causing whine - what to replace/buy

I'm hoping someone can help with a troubleshooting / purchasing issue. Thanks in advance!

Here's the gear I'm working with:
  • M-Audio DMP3 mic pre-amp (two inputs)
  • ART TubeMP Studio pre-amp (one input)
  • MXL 993 condensor mics (two)
  • Studio Projects C1 mic (one)
I want to use the MXL 993s with the DMP3. However, I am getting a high-pitch whine in both channels. The initial data points do make it seem like it's an issue with the mics:
  • It takes a minute or so for the whine to start. This tells me that the whine is not just background noise, because if it were, it would happen right away.
  • The whine shows up in recordings, even if I record with all headphone/monitor outputs disabled. This tells me it's not an output issue, and not a feedback issue.
  • The whine gets louder as I increase the gain.
  • It is not the same whine in the two channels - it's a different pitch, pattern, and volume. If I reverse the mics onto opposite channels, the whine reverses channels too.
However, there are some additional data points that make me wonder if it's actually the interplay between the microphones and the particular pre-amp that is causing the whine:
  • If I unplug one MXL mic from the DMP3, the whine appears to go away for the remaining mic. But if I increase the gain in the active channel, the whine comes back.
  • If I plug one MXL mic and one Studio Projects mic into the DMP3, the MXL mic has the whine but the Studio Projects mic does not.
  • If I plug either of the MXL mics into the ART TubeMP Studio pre-amp, there is no whine, even if I jack the gain all the way up.
So, given these things, I'm wondering if the issue is that the MXL 993s are finicky about their phantom power, and the DMP3 is not providing it well - and that how well the DMP3 provides it is somehow related to the gain and whether it is providing power to one or two mics.

I don't know electric stuff at all, so I apologize if this is the dumbest thing you've ever heard.

Any how, if anyone can tell me if this sounds like the right explanation, I'd appreciate it. Assuming it is the right explanation, what's the best way to deal with this?
1) New pre-amp to replace DMP3? (If so, what do you recommend?)
2) New mics to replace the MXL 993s? (If so, are there particular brands that I can feel confident aren't so finicky about their phantom power supplies?)
3) Some kind of external phantom power adapter (like the Behringer PS400) that presumably provides more consistent power than the DMP3? (If so, what brand/model do you recommend?)
4) Something else?

Thanks again!
Old 7th September 2011
  #2
Lives for gear
 
Silent Sound's Avatar
Well, it sounds as though you've done a good job testing out different scenarios and narrowing the problem down. If I were to speculate a reason, I'd lean towards the DMP3 having a phantom power issue or some strange input impedance mismatch with the MXL 993. In any case, I'd get a different microphone than the MXL 993 or just use it with the ART TubeMP only. I'm just not a big fan of that mic. Maybe look at a used Oktava MK-012 or Peluso CEMC-6. They're a bit more money, but if you're going to replace the mic, you might as well upgrade it to something better.
Old 7th September 2011
  #3
Gear Maniac
 
portishead's Avatar
 

What interface are you using to record with?

I've has this happen with the Presonus FireBox through it's front inputs.
Old 7th September 2011
  #4
good ol' maudio....

Yes, replace the preamp with...anything.

Don't even bother modifying the thing. I could try and suggest some fixes, but I won't bother.

As you can guess, not an maudio fan here.

Anybody else here old enough to remember when they were "Midiman"?
yuck.

My apologies to maudio fans.

Flame away.

My first truly obnoxious post. Couldn't help myself.

j

EDIT:

There is one exception, a GS member posted some clips of the Sputnik, and another one reviewed it for a magazine I think. It is a pretty good mic, as it has not much in common with their other products.
Old 7th September 2011
  #5
Lives for gear
 
Jimsi's Avatar
 

first?...joking, i owned m-audio stuff and heard of them when they were Midiman...i wont go back....86 the idea...
Old 7th September 2011
  #6
Lives for gear
Does the M audio interface have dedicated Line inputs for outboard line level gear such as your outboard pre amps?

And if so you are you using those with XLR to TRS cables to patch the pre's to the line ins?

If the interface does not have dedicated lines ins does it have mic/line xlr/trs combo jacks? if they are combo jacks are you patched into them with xlr to TRS cables?
Old 7th September 2011
  #7
Here for the gear
 

For those who asked: The audio interface is an M-Audio Delta 44. The mics are connected to the pre-amp by XLR cables, and the pre-amps output to the Delta 44 via TRS cables.

If I am doing stereo miking, does it matter if both mics are going through the same pre-amp? I know that matched mics are recommended, does the same apply to the pre-amp somehow?

Basically, I'm wondering if the easy/cheap solution is to get another ART TubeMP Studio pre-amp. That seems to drive the MXL 993s just fine, so I could plug each MXL into an ART pre-amp. Then I could still use the DMP3 for my vocal mic.

Thanks again, all!
Old 7th September 2011
  #8
Lives for gear
Quote:
Originally Posted by crossatlantic View Post
For those who asked: The audio interface is an M-Audio Delta 44. The mics are connected to the pre-amp by XLR cables, and the pre-amps output to the Delta 44 via TRS cables.

If I am doing stereo miking, does it matter if both mics are going through the same pre-amp? I know that matched mics are recommended, does the same apply to the pre-amp somehow?

Basically, I'm wondering if the easy/cheap solution is to get another ART TubeMP Studio pre-amp. That seems to drive the MXL 993s just fine, so I could plug each MXL into an ART pre-amp. Then I could still use the DMP3 for my vocal mic.

Thanks again, all!
Just asking..Are the inputs on the Delta balanced..?
Old 8th September 2011
  #9
Here for the gear
 

Quote:
Originally Posted by Snatchman View Post
Just asking..Are the inputs on the Delta balanced..?
Yes.
Old 8th September 2011
  #10
I am going to chime in and guess that it is a phantom power issue as well. I had a similar issue with a Mackie interface and finally narrowed it down to the pahntom power. I dont have any ideas on how to fix this other than to buy a dedicated phantom power supply. Rolls makes a fairly good unit that can be had for pretty cheap especially if you buy used on ebay.
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