Hum via XLR

[snippet]

Hi

 

Can anyone offer any advice?

 

I am using a focusrite saffire audio interace for home recording and very pleased I am with it too.

 

I have been recording vocals via a very very old shure mic through the jack input.

It had worked fine with no hum but just not a brilliant sound.

 

So I bought an alternative mic that was in my price range, the studio project b1 mic.

It didn't come with an XLR cable so I bought one seperately.

 

I have just plugged it into the saffire with a 2m XLR male to female and there is a noticeable hum .

Its not terribly loud but its noticeable.

 

Is this likely to be a faulty cable?

A cable which is too short at 2m?

Could the mic be at fault?

 

What d'ya reckon?

 

Thanks very much

[saturnx21]

Hi there

 

Check that the XLR is wired correctly (I have bought quite a few new ones that where wired incorrectly!!!)

If the XLR is correct then it is likely to be the mic.

 

 

HTH

 

;)

[snippet]

Thanks but I can't really check the wiring as its sealed

[paulears]

Does the hum change when phantom is turned off?

 

Also, does the hum go up and down in level as you change the gain?

[snippet]

Yes it goes up if I turn the gain up.

 

The hum still shows as an audio signal when recording when the phantom is turned off and is really noticeable when I normalise the sound

[paulears]

the increae when normalising is well, 'normal'.

In view of the level going up and down, then it all points to cabling being the most probable cause. First thing is to swap the XLR for a know good one and see if there is a difference. One question - does the mic actually work as in produce sound? If so then pins 2 and 3 must be ok as it wouldn't work if the phantom wasn't getting to the mic, and the audio getting back to the interface. The likely scenario is no pin 1 connection - but this in itself would not automatically generate hum - but best to change the cable first and see.

[snippet]

Thanks Paul, always so helpful.

 

"One question - does the mic actually work as in produce sound?"

 

Yes, if I sing through it I can record my dolcet tones.

 

I'll try and pcik up a cable tomorrow.

 

Would a standard XLR from Maplins do the trick?

[Simon Lewis]

If so then pins 2 and 3 must be ok as it wouldn't work if the phantom wasn't getting to the mic, and the audio getting back to the interface. The likely scenario is no pin 1 connection...

 

Doesn't phantom require pin one to be connected in order to complete the 0V return?

 

I wonder whether cable shield is connected to the XLR shell?

[kev-no1987]

I've had a problem with XLR's in recording, the hum problem poped up when I was recording vocals through a drawmer Pre amp.

 

The problem turned out to be the lights in the room they where causeing the hum but I never noticed this with dynamic mics just with condensiers. My advice would be to check the lighting in the room.

[snippet]

I'll try the lights thing but its a 60 watt with no dimmer so...........

 

Nah, lights didn't make a difference but thanks anyway

 

In fact I turned everything off I could and still no difference, I'm hoping its just the cable.

 

Fingers crossed

[dirkenstein]

The other likely scenario is that pin 1 and 2/3 are swapped, resulting in one of your balanced signals ('hot' or 'cold' side, doesn't matter which one) travelling over the screen instead of the twisted wire pair in the cable.

This always introduces a largish amount of noise.

 

I have previously bought a K&M microphone arm (the spring loaded table clamp kind) with a prefitted cable wired this way, much to my surprise.

 

And yes, a standard Maplin XLR will work fine (for a given value of 'fine').

 

Anybody know if there's an alternative wiring standard for XLRs used elsewhere on earth?

[paulears]

I have to say I was talking complete b*llocks - so helpful it wasn't. What I meant to say, but got wrong, was that the audio path via 2 and 3 must be intact, but maybe pin 1, which as was put right for me, is essential to power up the mic - so maybe something as daft as a poorly made solder joint on pin 1 could be part of the problem. No doubt a visual inspection and then a hot iron to reflow any dry joints could put the matter straight, and solve the hum.

[snippet]

The strangest thing!

 

Ok, I tried it with a different lead and the sound is gone but also tried it with the original lead and the sound is gone as well!!!

 

Don't know if this is going to come back again but for now it seems ok.

 

Apart from a dodgy lead where the wiring is slightly out I can only think of a an external (to the pc) electrical devise causing the noise.

 

Thanks for your help.

[timtheenchanteruk]

Anybody know if there's an alternative wiring standard for XLRs used elsewhere on earth?

 

doesn't america use a different XLR wiring "standard" I seem to remember something on Sabine FBX, I seem to recollect pin 1 hot??

[jamesperrett]

Anybody know if there's an alternative wiring standard for XLRs used elsewhere on earth?

 

doesn't america use a different XLR wiring "standard" I seem to remember something on Sabine FBX, I seem to recollect pin 1 hot??

 

Pin 1 is always the ground but some gear is wired with pin 3 hot and pin 2 cold. Even worse, I have found some unbalanced gear wired with pin 3 hot and pin 2 not connected at all.

 

The standard, which has now even been accepted by US manufacturers is to make pin 2 hot, pin 3 cold and pin 1 audio ground.

 

Cheers

 

James.