Problem With My DMP3

T

taylorguitarman

New member
I've been having this problem with my DMP3 lately where when I plug in two condensor mics I get a lot of electrical hum (even at low gain). If I unplug one of the mics (leaving the cable in and out of the pre) it goes away. I've tried swapping cables but I get the same thing. I've to narrow it down to one of the channels but that doesn't seem to matter. It works fine with two SM57s though or one condensor and one SM57. I haven't tried all of the combinations of my mics but I get it with 2 603's, an MC012 and a M179, a 603 with an AT3035, and a V67G with an AT3035.
Any ideas at what could be the cause and what I could do to troubleshoot/fix it?
I've been looking to buy a Sytek lately but I'd like to keep using this one too.
 
sorry, sometimes you have to start at the basic possibilities. lets review:

when using one sm57 phantom power button is pressesd out. (no red light)

if a 57 and a condensor mic (603's, MC012, M179, AT3035, etc) are being used at the same time, then the Phantom power button is pressesd in! (red light)

if you're using 2 condensor mics (or just one) the phantom power button is pressed!

if you're using any dynamic mic (sm 57, sm58, etc) phantom power button is out!

Is this what you're saying?...I've had your similar problem when I've got to caught up in mic and pre switching especially tracking drums and have forgot to switch Phantom back!...I wasnt real clear on your response, so just trying to get clear before ruling that out.
 
I have had this exact same problem. Two weeks ago, I shipped mine back to M-Audio, where they were unable to reproduce the problem after several tries. It's currently in transit back to me.

Quite disappointing, since I bought the thing to do stereo setups for drum overheads, acoustic guitars, etc. It sounds great, but the hum with two condensors makes it almost useless to me.

And yeah, mine is exactly the same. Search for threads that I've started, and you should see the one where I'm complaining about this.

Hal
 
BTW, once it comes back, I'm planning to get the Rolls PB223 two-channel phantom supply to use instead of using the one in the DMP3. It's $50 at music123.com, which is cheaper than buying a new preamp, and since I only paid $120 for it, I suppose it's fair. :/
 
That might actually be a good idea, since I think it has something to do with the phantom power. That would allow me to go add a couple more 'phatom' channels to my AW16G too.
And Bobalou, it only hums when I have two condesers plugged in and the phantom power on. Every other combination I don't hear it. I didn't have this problem when I first bought it (used), it's only happened recently when I've been using two mics again.
 
Flipping the phase canceled out the hum, so it's useable again. Thanks Richard, good idea. I still think I'm going to look at getting a phantom power supply for my workstation though, I'd never thought about doing that before. What's a good phantom supply? Would the AT 4 channel (CP8506) work fine or is there a more popular one?
 
Perhaps a silly question, but

Won't one of his mics be out of phase now? How does he use both of them simultaneously if one's out of phase? :confused:
 
My guess is, his mics were already out of phase. By reversing one of them, he put them back into phase. I believe he was experiencing the dreaded "phase problems" you've heard so much about from the beginning. If the mics were coincedent, he may have a cable that has reversed pins. Otherwise, the positioning of the mics relative to the source may have put them out of phase in the first place. It was a shot in the dark, but an easy thing to check. It's hard for me to address, because I'm not a techno-geek. I don't really understand how all these mysterious boxes with blinking lights work, but I know how to jury-rig recording and live gig gear. Sometimes that can help me to help someone else, because I don't know enough to look for the complicated explanation, or the complicated solution. I just try to make sure that my suggestions won't blow up anybody's gear, and I figured doing a phase reversal check couldn't hurt anything.-Richie
 
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