Phantom Power Hum

[mbenny123]

What causes hum in phantom power? Is there a way to replace a bad component? The phantom power in my board is starting to hum.

 

[antispatula]

try plugging the mixer into a different socket, it's possible your mixers power isn't grounded correctly.

 

[RezN8]

If it's a grounding issue, try http://www.ebtechaudio.com/he-2des.html

If it's starting to hum along with the tunes, maybe it's because it likes the music -- just ask it nicely to stop.

(sorry, couldn't resist the pun.)

 

[MOFO Pro]

Is it the phantom power... or the device you're powering...

Same symptoms on different mikes?? How about a dynamic mic, is that connected at the same time? Does it hum when you engage phantom power with nothing connected?

Most hum on a desk is not the board... but what you hook up to it...

 

[mbenny123]

Same symptoms on different mikes??

Yes, but some mics the hum seems louder.

How about a dynamic mic, is that connected at the same time? Does it hum when you engage phantom power with nothing connected?

Hums with a)dynamic mic connected, b)only 1 condenser mic connected, and c)without anything connected to any channels (though the hum is quite faint then, but I still notice it appear as soon as I flip the phantom on switch).

Tried switching outlets, circuits, different power strips, no power strip at all, etc.

 

[MOFO Pro]

Sounds like it might be a bad cap in line with the +48 transformer tap of the power supply... Does your desk have a din plug with isolated voltage feeds, or just a two conductor wire? If it's two conductor, the problem's in the mixer, if din... then you could try another supply.

 

[antispatula]

try plugging in a mic, then setting it down. I know that when I hold a mic, I get a hum, just from the electricity in my body or whatever.

 

[mbenny123]

Sounds like it might be a bad cap in line with the +48 transformer tap of the power supply... Does your desk have a din plug with isolated voltage feeds, or just a two conductor wire? If it's two conductor, the problem's in the mixer, if din... then you could try another supply.

Are you talking about the ac/dc converter cable that powers the mixer? If you are, the answer is it's a 3 prong round plug, with three wires going into the desk.

 

[MOFO Pro]

Hard to say from that... what's the model of the mixer?

 

[mbenny123]

what's the model of the mixer?

Well, it starts with a B, and ends with ehringer, model MX1604A...

http://www.behringer.com/MX1604A/index.cfm?lang=ENG

 

[dgatwood]

Hums with a)dynamic mic connected, b)only 1 condenser mic connected, and c)without anything connected to any channels (though the hum is quite faint then, but I still notice it appear as soon as I flip the phantom on switch).

Hmm. If it were leakage from the phantom power unit into the signal lines, I would not expect it to diminish so greatly when no mic is connected. In fact, I would not expect it to diminish at all. If anything, I would expect it to diminish with a mic connected due to the mic drawing down the current. I'm wondering if the ground side of the device's internal power supply (and the ground side of the XLR plugs and everything else in the mixer) might be floating, and might be getting some leakage from something like dendritic growth across an electrolytic capacitor leading to a near short condition and dumping AC into the case.

You might try the "ground the heck out of it" method.... Go to your nearest hardware store (or even a discount store like Wal-Mart) and buy yourself a power plug. Not a cord, just a bare plug. Connect the ground pin to a piece of 10AWG (or so) wire, and connect the other end to the shield of an audio plug. Be absolutely certain (using electric tape) that the wire cannot come loose and short against a hot contact in the plug (or really, even a neutral contact). Plug the plug into the mixer, then plug the power plug into an outlet. Turn on phantom power and see if the hum is gone.