light buzzing in audio

[sam.spoons]

Fortunately, for most folks with a balanced output mixer needing to link to an unbalanced input, the mixer will be of the cost class that doesn't feature output transformers. :)

 

Or servo balanced outputs either http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif

[KevinE]

Contrary to normal practise, Behringer specifically recommend linking 1&3 on XLR balanced outputs if you want to feed into an unbalanced input on an amp. (it's in the manual..)

[mackerr]

Contrary to normal practise, Behringer specifically recommend linking 1&3 on XLR balanced outputs if you want to feed into an unbalanced input on an amp. (it's in the manual..)

 

Contrary to your practice perhaps, but that would be standard practice for people who want the best noise performance. See the Rane Note 110 that was referenced in a couple of earlier posts in this thread.

 

Mac

[KevinE]

Contrary to your practice perhaps

 

er no, some electronically balanced output stages can be damaged by 'unbalancing' the output with a shorting link. A previous post mentioned this, and I added that the behringer permits it.

 

Only cross-coupled output stages can be referenced in this way and of course floating transformers. Many electronically balanced line drive outputs in our industry, particularly older analogue stuff can be damaged, sometimes slowly over time. Certain models of FOH desks will pop their fusible op-amp supply resistors if you try it..though most will not be subject to that sort of misuse.

 

If in doubt therefore, the safest way is to use one leg and put up with the signal loss...or use a balun.

[paulears]

I thought I posted this yesterday, but Sound on Sound have a great article on this subject - not sure if you need to have a subscription to view it, but you can try this link.

 

Diagrams explain it pretty well, I think!

[sam.spoons]

I thought I posted this yesterday, but Sound on Sound have a great article on this subject - not sure if you need to have a subscription to view it, but you can try this link.

 

Diagrams explain it pretty well, I think!

 

I'm sure you did somewhere Paul, I looked at it http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif

 

Contrary to your practice perhaps

 

er no, some electronically balanced output stages can be damaged by 'unbalancing' the output with a shorting link. A previous post mentioned this, and I added that the behringer permits it.

 

Only cross-coupled output stages can be referenced in this way and of course floating transformers. Many electronically balanced line drive outputs in our industry, particularly older analogue stuff can be damaged, sometimes slowly over time. Certain models of FOH desks will pop their fusible op-amp supply resistors if you try it..though most will not be subject to that sort of misuse.

 

If in doubt therefore, the safest way is to use one leg and put up with the signal loss...or use a balun.

 

I mentioned it in more than one post in this thread. I also pointed out that a cable with pins 1 & 3 shorted does not always solve the noise issue. It's often a case of 'suck it and see' with noise on balanced outputs feeding unbalance inputs. Try the "pin 3 lift" cable first, it can't damage your desk outputs, if you get no signal you'll know you have cross-coupled or transformer outputs and can safely use a cable with pins 1 & 3 shorted.

 

 

 

[MarkPAman]

I thought I posted this yesterday, but Sound on Sound have a great article on this subject - not sure if you need to have a subscription to view it, but you can try this link.

 

Diagrams explain it pretty well, I think!

 

You did! Different thread though.

[paulears]

I wish the search function worked! Cheers Mark

[IA76]

Hi All

 

I tried all the cable methods mentioned but it didn't cure the problem.

 

One of the main mixer outputs is used to feed a http://www.behringer...ucts/MX882.aspx which feeds audio to a camcorder and also a pc for recording audio. On the recorded audio I could faintly hear the buzzing/humming in the background.

 

What else could be causing this problem and how else can I try to cure it?

 

Just check that the buzz doesn't change as the lights are dimmed up and down = if it does, then it's coming from the dimmers, probably being carried by the mains cabling.

 

Hi Paul

 

All the lights in the building are fluorescent tubes.

 

 

 

 

 

[paulears]

I was thinking dimmers - they're a major player in the interference stakes, and the sound of the interference changes as lights dim, which gives you a direction to stick your nose into. If you have no dimming equipment, then forget it!

[Hilary Watts]

Is the gain structure of the mixer set correctly? I've got a similar mixer and if the input signal is too low or the gain or input fader (or possibly a sub fader) is set too low and the output faders raised to compensate then the internally generated self-noise is quite noticeable.

 

Can you lower the output faders and increase the input without overloading the early stages and creating distortion?

[GR1]

If I were recording to anything other than a Pro Camcorder with a balanced line input I would use a DI box or transformer in case the input is a high impedance mic level input. For the PC recording I would use an interface like a UCA222. This would improve the situation but might not entirely fix it. Pro camcorders are expensive for a reason and audio input flexibility is one of them.

[sam.spoons]

That mixer appears to have balanced inputs so presumably you are using balanced XLR leads to connect to it. This is a different issue to the original post isn't it? You originally were having problems with an unbalanced input on an InterM amp?

I gather you haven't solved that one either so the two may well be connected. Does the noise go away when you record from the Berry desk without the InterM amp being connected?

Fluorescent lights can cause interferance sometimes, does it go away when the lights are off?

We use one of these http://www.maplin.co...-isolator-vw43w to isolate laptops from the desk when noise from the PSU gets into the audio. It's reasonably cheap and works okay, as a last resort it may help you.