Multicore issue

[Pattern123]

Hello all, I am using a relatively new CPC bought multicore between control room & stage (18 send, 4 return) we have stereo returning from desk to Amp via stage Box and have used up to 12 Radio Mics on the stage sending down it to our desk - no problems.

 

Last show we tried at the last second to send one way of ASL talkback back down a return to the stage, and had intermittant problems with it, with the call coming on and getting stuck and a strange noise, like a regular 'clicking' appearing on the system. After eliminating & testing every other potential cause, I bypassed the multicore and removed the issue.

 

Current show, same problem occurred (Short term memory loss) with the same solution. Yesterday I tried to send a signal (Line out on Aux from desk) back down a return to get to a powered monitor in a backstage area, loud buzz on the signal and same 'clicking' noise regular intervals in background, with the signal still being heard, but only just above the buzz. Tried sex changing at both ends and using a Mic send which I knew had worked - same problem. Tried swapping to one of the Amp lines I knew to be working - clear as a bell.

 

Anyone any ideas?

[Brian]

Anyone any ideas?

Comms problems like that are often down to multiple earths. There should only be one and it should be at the power supply. Take a meter to your multi and check that every line is continuous and separate from every other line including all your earths.

 

 

[E2A]

As it says somewhere...

 

NOTE: To prevent shock hazard, ground loops, and noises, NEVER connect line connector Pin 1 (common) directly to the station chassis. In addition, never connect Pin 1 to the shell of the mic cable.

[dbuckley]

Comms lines are unbalanced, and thus can get interfered with in a way that balanced audio is immune to.

 

Perhaps your aux out (or your cabling to it) is unbalanced too?

 

As brian notes, serious examination of earthing (both power and audio) should shed light onto whats up.

 

Regular ticking sound - if you were here in New Zealand I'd say you're within a few miles of an electric fence :) They play havoc with all kinds of things...

[TAG1960]

I had a friend who had problems with a cheapo multicore (I shall mention no names), and the faults turned out to be two fold, 1. some channels were wired incorrectly (ie earth on pin 2 instead of pin1) so all looked good on a cable tester, but open all the XLRs and the fault was visible. 2. cheapo multis use cheapo neutric look alike XLRs which deffinatley do not have the same properties. Many made very intermittant connections. We replaced the lot with Neutrics and hey presto...no problems.

[Pattern123]

Thanks for the replies, yes something to do with unbalanced/unscreened signals & cables, but found cause of the noise was the earth on old Hi-Fi Amp which drives our control room monitor speakers, when I lifted the earth it was clear as a bell, both monitors were being fed from the same unbalanced output on the desk. I suspect there is still an issue with the multicore, will have a look at it over the summer holiday.

[tb1979]

Just double-checking here: when you say "earth", you do mean the thing in the 13A plug on the hi-fi unit? You did reconnect it before using the hi-fi any more didn't you? Huge apologies if that's a 'granny sucking eggs' question, but if it is you'll know why I wanted to clarify for anyone reading this thread in the future

[Pattern123]

Yes indeed, should clarify that having lifted the earth and eliminated the noise, I reconnected it and swapped it for a newer Amplifier which didn't cause the same issue.

[tb1979]

Phew! Hope you didn't mind me asking, but it's always good to clarify these things for whoever ends up reading this thread for inspiration...

 

Don't run your sound equipment without earth connections, kids ;)

 

[/public service announcement]