Help! DMP3 Mic preamp/phantom power/low end hum

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capnreverb

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I just got in the mail a DMP3 as my first intro into mic pre-amps outside of the ones in my main mixers. I plug it into my board, and try it out with a sm57 and a beyer 500. Sounds great. So, i plug in a condensor mic and press the 48v, and low end hummmmmmm. I thought it was the C4, so i plugged in my at4033, and its still there, but not quite as loud. Then I notice the lights dim a bit and it mostly goes away. Not totally, but enough that I am not angry. Lights change a bit, and the hummmm is back as loud as ever. So, I assume it's a grounding problem. I try a differant outlet not connected to the same appliances as the other and --- hummmmmm. I'm sure it's a grounding issue in my crummy apartment. The only thing that makes me wonder about all this is that the phantom power in my alesis studio 24 does not have this problem plugged into the same outlets.

If i buy a power conditioner will it solve my problem? I have also seen devices that are kinda expensive that give out a constant unchanged current. Will this solve my problem. Is it the fact that the studio 24 has a grounded plug, and the DMP3 has a non grounded wall wart?

Any suggestions?

PS, i don't think my landlord will spring the $ to have this 70 year old building rewired to make my studio sound hummmmmmm free?

Any advice is greatly appreciated.
thanks,
-wietlispach
 
There is phase switch on the back. You may try that. Seems I had some hum problems a long time ago, pushing that switch fixed the problem.

But, sorry to say, the unit may have been damaged.
 
phase switch did not change hum.

Thanks for the suggestion
 
you may have a ground loop. make sure everything that's connected is plugged into the same outlet - including the computer.
 
Hey capnreverb,
Where do you live? Do you live in Europe? I had exactly the same problem with the DMP3 that I bought from the US. I was using a step down transformer to convert the juice to 230v(I live in France). The hum was terrible, but I bought the EU version of the power tranformer and it went away.

I ask becausee of your comment (wietlispach).
-Simmons
 
Don't know if it will work, but you could try one of those adapters that has no ground plug on it, I've heard sometimes that can help because things might be double grounded or something. But that's just a random suggestion.
 
I'm a fan of a lot of M-Audio products, but the DMP3 left a bad taste in my mouth. I went through 3 of them before giving up entirely. The ones I had suffered from noise/hum, noisy pots, and even a strange phase reversal when engaging the HP filter. I'd suggest getting a replacement from the dealer, as it's probably defective.

Jay
 
With the lights dimming then coming back it sounds like a problem with the unit. I'd recommend you return it any try another one.

Best of luck with it.
 
Fletcher said:
With the lights dimming then coming back it sounds like a problem with the unit. I'd recommend you return it any try another one.

Best of luck with it.
Click to expand...

I'm here in the usa, even with my very Euro last name (Swiss I believe), and thanks for the response.

I was not totally clear in the light dimming issue, the lights were dimming slightly in my home lights, not the preamp lights.

The odd thing is that the next day I tried it again with nothing changed in terms of setup and it was gone. Later that night it was there. I wonder if there is something in th powergrid like an ac unit or microwave somewhere else in the building messing with me.

Is there some magic grounding powerstrip or rackmount that solves grounding issues, or is the only resolve involve massive rewiring/electrician issues?

Thanks you all for your helpfull coments
-wietlispach
www.soutrane.com
 
Sounds just like the ground loop issue that I had to deal with a while back. I bought the "HumX" from Ebtech and it cleared the noise out of my power line completely. Nice thing is that it doesn't interfere with, or get plugged into, the signal path at all, only the power line in.

Hum X: http://www.ebtechaudio.com/new.html

EDIT: I almost forgot to suggest that you search the forums here to find my earlier posts about my ground loop problems for more details.

Hope this helps!

-mr moon
 
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