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Guys I have just connected a studio microphone to the phantom power which inturn is connected to the sound card (m audio) which is also in turn connected to my PC using a usb port. The problem am having is that when I record audio, I hear a hum noise. I don't want to fix the problem during mixing. I want my vocals to be recorded without any noise. Please someone help n guide me. Thanks

  • Are you using a balanced XLR cable? – deepsweet Jul 25 '14 at 8:12
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Make sure that the microphone cable is not running close to any (switching) power supply. You should already be using a balanced microphone cable: those can take a lot of electromagnetic abuse but there are limits.

Ground loops are not all that likely with the described setup: even if the USB sound card has a power supply of its own (you did not go into this level of detail), this is likely of the wall wart variety without an actual ground line.

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Hum can really only come from one of 2 places. Either the microphone element is picking it up or it is being induced in the signal path. Here are some things to try for each scenario

1)

Lights, some kinds of light fixtures especially florescent can induce quite a bit of hum into a microphone. Try turning off the lights and see if you hear a difference.

Go to another room, some times if there are enough electrical cables running the walls in the room you are in you can end up with some nasty induced hum

2)

Make sure all of your devices are plugged into either the same outlet or a pair of balanced outlets. Since wall power is AC and most if not all audio circuitry needs DC your devices all have their own transformers and rectifiers in them. Most house outlets are slightly out of phase of each other due to the way they are wired. The older the house the more apparent this may be. Some of the AC wave form will always slip through your converters and can cause some nasty hum by making your devices slightly out of phase of each other (speakers, interface etc.)

External phantom power units (I assume thats what you are using here) can cause a bit of hum as they are not really intended for recording use. Most of the interfaces worth using with mic pre amps in them also have phantom power. If they dont get your self one that does or get a decent mic pre with a phantom power driver

Does your mic need phantom power? For that matter what mic are you using? Phantom power Driver? Interface?

Get your self some shielded cables they make quite a big difference

Make sure every thing is grounded properly. i.e. if your device has a 3 prong wall plug make sure it is plugged into a properly grounded socket.

There are lots of potential issues here. If you post the equipment you are using we can better help find the possible issue.

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hum can come from a number of things. could be the mic cable, so try another one if you have one. Not sure what you mean by "phantom power"?!? Is that a stand-alone unit for the mic or a mixing desk or some other device or ??? How is it connected to the sound card? Try other cables there as well. Also, computers & monitors can introduce hum, make sure everything is as far away as possible.

Also, you should try and track down which piece is generating it by hooking up just the sound card and monitoring the input in your DAW. Then add the phantom power source, then the mic cable, then the mic. See what piece introduces the hum.

  • Thanks so much. I will try the cables coz really I suspect they are the ones that could have a problem – brian mwiinga Jul 25 '14 at 17:49
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'Phantom power' is voltage provided along the microphone cable for microphones who need it. It is phanom because it does not affect regular[dynamic] microphones in any way.

As above the cord is the first suspect. an ungrounded powwer supply can cause a ground loop so check the power supplies and better still keep all the connections tied to one ground spot.

Multiple grounding routes lead to voltage differences and current flow hence 'hum'

  • The term "Phantom Power" has nothing to do with the fact that dynamic microphones don't need it. Neither do "electret" microphones. Phantom power is simply a term for the method of providing 48v to condensor microphones over the balanced signal lines. – Mark Nov 24 '16 at 14:59
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My problem with bad hum was simply to turn off the preamp-amp of the HiFi system when recording from microphone. Turning it off cut all input signals (CD FM, cassette and possibly a low, inaudible hum from speakers but does not affect the Mike input since it comes in directly from plug (TEAC 3300), and not from amp/receiver. Doing it this way eliminated possible 60 mhz loop hum, and other source hums (like from bad capacitors), and my recording from microphone was a clean as could be. The only problem is that you cannot immediately compare the tape and source signals to hear whether the recording levels are OK. You do have to have the whole system ON to playback your tape. But a little experience with setting the tape input levels, and reading the VU meter helps with that problem. It's worth a try, just cut out everything but your mike.)

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