DMP3 Preamp HUMMING...NO SOLUTION

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cadbawdbawks

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PROBLEM SOLVED - Solution underneath!

I have an M-Audio DMP3 mic preamp that just doesn't want to stop making a low humming noise. I've tried everything to my ability including spreading out the cables and moving them around to make sure that they are not twisted together, plugging the power supply into the wall and different sockets, using a 3 prong to 2 prong converter for the power supply, using different xlr and trs cables, using different mics. Everything leads right back to a low hum that gets unacceptably loud with any significant raise in gain. The low humming begins as soon as I turn on phantom power. I've tried using the built in preamps that came with my interface with the exact same cables and mics and there was no humming noise to be found. This is driving me crazy...

One thing i should point out is that my ac adaptor is an OEM UK one which I have plugged into a universal adapter to change it to a 3 prong North American plug. Don't know if that could cause any problems, I haven't been able to find the original M-Audio DMP3 ac adaptor anywhere for sale. The M-Audio online store is all out of stock on it.

So here's how I have everything hooked up just for your info:

Condenser Mic --> 25' XLR Cable --> DMP3 In --> DMP3 Out --> 20' TRS Cable --> Tascam US 122 Interface Line In

The power supply and adapter:

57149491.jpg

65017577.jpg

60708777.jpg

69549935.jpg


Thanks! Your help is much much appreciated!

-------------------------UPDATE!!-----------------------------------UPDATE!!-----------------------------------UPDATE!!-------------------------------

SOLUTION FOUND!

I missed the obvious fact that North American sockets are 110V and British sockets are 230V and since my wallwart is not a dual voltage adapter, a step up transformer would then be of much importance. So I went around looking for a place that sells voltage converters (aka step up transformer) and I happened to stumble across a local foreign electronics store that sold 100W step up/down transformers for only $20 CAD. I brought it home, plugged it in, and what do you know, not only does the preamp turn COMPLETELY SILENT but the lights in the vu meters are glowing bright yellow in broad daylight!

The uk wallwart was not getting enough input to output the full 9v (credit to Johnsuitcase for figuring that out) and hence the preamp began buzzing on phantom power (buzzing = straining the preamp to squeeze out excess power on 48v) and the lights were barely going on.

I hope this is going to be of some help for those who are experiencing the same/similar issues.

Thanks again for everyone's help! I really do appreciate it!
 
Last edited:
are you sure that the preamp is humming? have you tried to record without preamp?
 
Seidy said:
are you sure that the preamp is humming? have you tried to record without preamp?
Click to expand...

Hi thank you for the reply. I didn't mention but I actually did try recording with my Tascam US-122 built in preamps and there was no hum nor was there any noise whatsoever.
 
Last edited:
well i don't know what kind of sockets are you using. since i live in europe we have these kind of sockets:
grounding.jpg

and if there's a grounding issue, we just cut these grounding pins
 
Seidy said:
well i don't know what kind of sockets are you using. since i live in europe we have these kind of sockets:
grounding.jpg

and if there's a grounding issue, we just cut these grounding pins
Click to expand...

Hi thanks for the reply.

The north american plugs use something different.

they look like this:
124_cobis_20070206153048.jpg


Normally for grounding issues I would just use a 3 prong to 2 prong converter (a "cheat plug") since the lower 3rd prong is the ground, however that hasn't solved my issues.

Any other ideas? Thanks again!
 
cadbawdbawks said:
One thing i should point out is that my ac adaptor is an OEM UK one which I have plugged into a transformer to change it to a 3 prong North American plug. Don't know if that could cause any problems, I haven't been able to find the original M-Audio DMP3 ac adaptor anywhere for sale. The M-Audio online store is all out of stock on it.
Click to expand...

Dude,

This just sounds wrong. All you want is an adapter which plugs into your wall socket, and has an output suitable for the DMP3. From a quick google, looks like the DMP3 needs 9 volts AC.

You don't specify what the transformer you mention is, but if it's got a US socket on the output, I presume it is 240 - 110. So you're feeding 110 volts into the primary side of a 240 - 9 volt adapter.

If you have a multimeter, set it to ac volts, and check the voltage at the plug which connects to the DMP3. A 9 volt adapter should read about 12 volts with no load.

Amanda
 
commanda said:
Dude,

This just sounds wrong. All you want is an adapter which plugs into your wall socket, and has an output suitable for the DMP3. From a quick google, looks like the DMP3 needs 9 volts AC.

You don't specify what the transformer you mention is, but if it's got a US socket on the output, I presume it is 240 - 110. So you're feeding 110 volts into the primary side of a 240 - 9 volt adapter.

If you have a multimeter, set it to ac volts, and check the voltage at the plug which connects to the DMP3. A 9 volt adapter should read about 12 volts with no load.

Amanda
Click to expand...

Hi Amanda,

thanks for the thorough post.

I just posted pictures up in my original post as well as this one. I'm sorry I'm quite illiterate when it comes down to these voltages and amps. Does this help? Thanks again!

57149491.jpg

65017577.jpg

60708777.jpg

69549935.jpg
 
Can you plug your oem ac adapter straight into the wall? I suspect the confusion is, the thing you're calling a transfomer, is that white pin adapter.
A transformer "transforms", from one voltage to another. Like 240-110. I took it from your original post that you had a 240-110 transformer in front of your 240 volt input oem adapter, in which case your output voltage would be way low.

I take it the DMP3 is not under warranty. Can you take it to your local music store and ask for help?

Of course, the DMP3 could be faulty. Most likely a faulty electrolytic capacitor in the power supply.

Amanda
 
commanda said:
Can you plug your oem ac adapter straight into the wall? I suspect the confusion is, the thing you're calling a transfomer, is that white pin adapter.
A transformer "transforms", from one voltage to another. Like 240-110. I took it from your original post that you had a 240-110 transformer in front of your 240 volt input oem adapter, in which case your output voltage would be way low.

I take it the DMP3 is not under warranty. Can you take it to your local music store and ask for help?

Of course, the DMP3 could be faulty. Most likely a faulty electrolytic capacitor in the power supply.

Amanda
Click to expand...

Hi again amanda and thankyou for your reply.

I'm not able to plug the PSU straight into the wall because the UK pins don't match up to the North American sockets. That is why i need to use that universal white pin adapter which (for lack of a better term) "transforms" the ac adapter pins into the north american pins so I can plug it into the north american socket.

Unfortunately the DMP3 is a purchase from ebay and therefor, is not under warranty. I guess I could drop by a local music store but the charges are tremendous, I would like to leave that to my last resort. Could there be any other suggestions that could be done on my own?

Thanks!
 
You just need to put that european power supply away and buy a universal 110x9v american power supply. They make universal ones that have a variety of tips to hook to most devices. They will also have switchable voltages for various outputs. Pick the tip you need and make sure it's set on 9 volt and you should be good.

Hopefully it's not damaged from the high voltage. If youve left it plugged in for long, it may be toast.

Good luck, Rodney
 
I have a DMP3 too. Theres a little button on the back that says 'phase'. Does pressing that change anything?
 
I would recommend not plugging the unit back in until you know you have the right voltage to it. The pictures clearly show your wall wart wanting 230 volts at 50Hz. You're plugging into 120volts at 60 Hz. All other suggestions are moot at this point.
 
I use the exact same power supply shown in the picture. Do you get 120 V ?
 
quickmill said:
Where are you located? What voltage are you plugging into?
Click to expand...

We get 240 V here so i just plug it right in. If he's getting 120 he'll need to get an adapter. Back in USA it was all good, but I'm in Asia for now, I've fried so much stuff by plugging in directly :( Oh well just 2 more years to go :rolleyes:
 
There is No adapter. You would have to use a step-up transformer to use that power supply in North America. It's cheapest to just buy a universal wall wart (under $20 U.S.) and set it for 9 volts.

The wall wart is rated at 9 volts output ONLY at the specified input rating. If you plug it into anything other than specified, you will not get 9 volts.
 
Take your existing european wall wart to Radio Shack, and ask them to help you find a compatible one. You'll want 9v 1amp, based on the one in your picture. Make sure you have the right type of connector, as well.

Should work fine, cost about $10-$15 or so.
 
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