DMP3 Preamp HUMMING...NO SOLUTION

[cadbawdbawks]

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.

Great I'll try that today! Do you believe the european wall wart could be the cause to the humming noise? Thanks!

 

[johnsuitcase]

I'd be shocked if it wasn't the cause.

Anything is possible, of course, but that sounds like a likely culprit. If the transformer is expecting 240volts to make 9volts, but is only getting 110, it's probably only outputting 4.5v or so. That may be enough to operate the opamps in the preamp, but not enough to get the full 48v for phantom power, so as it tries to sustain that constant voltage, the output voltage is dropping every cycle, thus the hum.

Getting the proper voltage, with enough amperage should solve that issue.

 

[johnsuitcase]

Wow thanks for all the replies above. I was just wondering though if purchasing a new wall wart would be a probable the solution to the humming sound. Could the humming come from using this european wall wart?

If so, I'm contemplating purchasing this wall wart:

http://cgi.ebay.com/NEW-M-AUDIO-COM...emQQptZGuitar_Accessories?hash=item58852ee7a2

Any good? Thanks again!

Looks like a good fit!

 

[darrin_h2000]

Hi thanks for the reply.

The north american plugs use something different.

they look like this:

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!

That causes those issues...you need that ground or you will get hum.

 

[cadbawdbawks]

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!

 

[johnsuitcase]

Glad to hear you got it working!

(I still think replacing the wall wart might have been cheaper and less possibility of problems, but if it works, go for it!)

 

[quickmill]

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

Forgive my pointing it out but credit should go to Commanda for figuring out that your transformer voltage was wrong.

 

[saads]

Commanda owns you now.