Hi,

I'm getting noise from 2 x mono unbalanced outs to 2 x mono balanced ins, and could do with clarification.

The unbalanced TRS cables are run from unbalanced outs, into XLR adapters, which go into balanced XLR inputs.

- The adaptor
http://www.maplin.co.uk/1-4-mono-socket-to-xlr-plug-43159

My question is: should two of the following cables fix it?
http://www.ebay.co.uk/itm/Balanced-Mic-Lead-Cable-XLR-Male-TRS-Jack-3m-Bla ck-/110763779533#ht_2415wt_1397

Even though each one these cables are stereo(?)

Many thanks,


Andy

If the source is unbalanced, TRS is just confusing the issue. You need a TS jack on the source and XLR at the other end. In between I'd suggest the SOS pseudo-balanced cable (look under Piranha Cables in the SOS shop). If that doesn't do the job you have a problem somewhere else. Depends what the noise is - it could just be noisy kit that's more obvious into a quiet mixer than a stage amp, say. Other noises could result from poor shielding or bad power supply or, well, pretty much anything in theory but in practice I hope somebody like Hugh will come along and stop me floundering.

One other possibility is that you're putting a low-level signal (unbalanced mike, or guitar, say) into a line input and by the time you've turned it up enough to hear it there's some hiss and stuff from the electronics there. Do check all this stuff before you buy anything. IF you can describe exactly what you're connecting to what we can help more.

You are almost suffering from ground loop noise.

The SOS pseudo-balanced cables are of a bespoke design which was conceived specifically to resolve this kind of problem cost effectively.

http://www.soundonsound.com/shop/Product.php?ProdID=424

Hugh

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Technical Editor, Sound On Sound

Thanks for the replies guys!

Interestingly, I swapped out for a cable of the same type, just a lot shorter, and in a different position (away from lots of other cables, and possibly some power lines).

The issues seems to have largely gone, but could prob be better

It was stated in the RME Babyface manual:-
When using unbalanced cables with the XLR breakout cable: be sure to connect the 'ring' contact of a stereo TRS jack, and pin 3 of a XLR jack, to ground. Otherwise noise may occur, caused by the unconnected negative input of the balanced input.

I'm coming out from a mains powered Novation Nova synth.

So is / was prob a combination of the ground loop and positioning. .

(just lastly, I didn't get an email notification about these replies. I'm not sure if anyone knows how to fix that. 'Favourite'ing the post didn't seem to have a effect)

Quote block:

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Interestingly, I swapped out for a cable of the same type, just a lot shorter, and in a different position (away from lots of other cables, and possibly some power lines).

The issues seems to have largely gone, but could prob be better

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Long unbalanced cables are more likely to pick up unwanted noises than shorter ones, and avoiding running the cables near power supplies and other equipment will help.

Quote:

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It was stated in the RME Babyface manual:-
When using unbalanced cables with the XLR breakout cable: be sure to connect the 'ring' contact of a stereo TRS jack, and pin 3 of a XLR jack, to ground. Otherwise noise may occur, caused by the unconnected negative input of the balanced input.

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Yes, the issue here is that some unbalanced adapters don't include a connection to pin 3 (cold) and hence the differential input amplifier doesn't have a proper differential signal to work with.

The SOS pseudo-balanced cable actually works in a slightly different way: it connects the unbalanced source between the hot and cold connections, and avoids any direct conenction to the ground, hence avoiding the risk of a ground loop.

Quote:

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I didn't get an email notification about these replies. I'm not sure if anyone knows how to fix that. 'Favourite'ing the post didn't seem to have a effect)

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You need to select the thread as a favourite, and then make sure that the option to send emails for favourite threads is enabled in your preferences. You'll find these options under the 'MY HOME' label in the blue bar at the top of the forum page, and then the Subscribe/Unsubscribe option at the bottom of the resulting page.

hugh

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Technical Editor, Sound On Sound

Great stuff Hugh,

Thanks for all the info

Will test further if the problem seems to need more attention.

Enjoy the weekend!


Andy