AndyJones Posted March 10, 2006 Share Posted March 10, 2006 Hello guys, We have a canford audio cans system that recently has acquired a large buzz. The buzzing is loud in some parts of the building, and fairly quiet in other places. Also the actual level (volume wise) changes dramatically around the building, for example, The cans on fspotLeft are barely audible from LX op cans, were as every one else can hear them fine. It's strange and annoying, I have tried some of the usual suspects earthing etc.. I guess I should tell you a bit about the system we have. We have at least 10 outlets, on each ring main (and and B) all powered by an amp from the stage managers desk. Hope you can help Cheers AndyJones Link to comment Share on other sites More sharing options...
Andrew C Posted March 10, 2006 Share Posted March 10, 2006 Just fixed a similar fault. Ours was caused by a poor solder joint in a cable. Fault finding? Wiggle the cables and connectors and see if it goes away. Link to comment Share on other sites More sharing options...
AndyJones Posted March 10, 2006 Author Share Posted March 10, 2006 caused by a poor solder joint in a cable. Fault finding? Wiggle the cables and connectors and see if it goes away. when the cable is wiggled on nearly all of the boxes there's always pops and crackles. the other day I managed to get cans feedback- a large squealing noise form a cans headset hung over a follow spot yoke, we could hear it from on stage, which is 1100 seats away. we are a three pin and 6 pin system, I'm guessing similar to DMX 2 pins are simply repeats? so therefore there shouldn't be any compatibility issues should there? Cheers AndyJones Link to comment Share on other sites More sharing options...
Dominicg Posted March 10, 2006 Share Posted March 10, 2006 I experienced the same problem however I managed to fix it 10 minutes before the show went up. The fault was a buzz on loop B, but A was silent. I found that it was the show relay at fault and after fiddling with that it seems to solve it. Also experienced a quiet spotter due to the headset being faulty, again down to poor wiring. Link to comment Share on other sites More sharing options...
Ynot Posted March 10, 2006 Share Posted March 10, 2006 when the cable is wiggled on nearly all of the boxes there's always pops and crackles. In that case I'd have ALL of your cables apart at the plugs/sockets and check/resolder them all. Check for twists in the cable, as well as partial breaks in the conductors, which may be anything up to 3 or 4 inches from the cable restraint. the other day I managed to get cans feedback- a large squealing noise form a cans headset hung over a follow spot yoke, This sounds like a normal problem (not a fault) whereby the spot op forgets to turn the mic off, thus getting feedback around the headset. Link to comment Share on other sites More sharing options...
Neil Hampson Posted March 10, 2006 Share Posted March 10, 2006 caused by a poor solder joint in a cable. Fault finding? Wiggle the cables and connectors and see if it goes away. we are a three pin and 6 pin system, I'm guessing similar to DMX 2 pins are simply repeats? so therefore there shouldn't be any compatibility issues should there? Almost but not quite...The three pin system refers to a single channel system i.e. everybody talks on the same ring, the 6 pin system has 2 audio lines so that 2 channels can be used, for example if the LX desk needs to speak to the spot operator to describe a long cue without affecting the SM calling the show then the LX and The Lime can switch their packs to channel B and everyone else can hear the SM on Channel A. A single channel beltpack can be modified for Dual channel use by makiing up a 'Y' splitter 1, 6 pin XLR and 2, 3 pin XLRs, however to swap channel you need to plug in the other XLR (doesn't work if you are part of a ring though) Link to comment Share on other sites More sharing options...
Brian Posted March 10, 2006 Share Posted March 10, 2006 It's worth remembering that the Canford/Techpro system is unbalanced audio, as such it can be prone to noise pickup from nearby cables. It's also worth noting that it is generally best to make sure that the only earth connection to the cable screen is at the power supply. Any connections to earth made at intermediate points, eg wall boxes, will increase the danger of noise pickup. Link to comment Share on other sites More sharing options...
Al Cain Posted March 10, 2006 Share Posted March 10, 2006 Have u checked the simple one, that all cables are connected properly, and theat all the conectors are clean?? Could be just a simple fault like this! ;) Link to comment Share on other sites More sharing options...
AndyJones Posted March 10, 2006 Author Share Posted March 10, 2006 eg wall boxes, will increase the danger of noise pickup. So could it be advisable to avoid contact from the metal casing of the connector to the metal wall boxes and railings etc? would something like lx tape or heatshrink solve this, on the casings? or just repainting the wall boxes? Thanks for your help so far when we get some dark time I might go and have a throwing out and repair session, Try and get the whole thing on six pins rather than a mish mash. cheers AndyJones Link to comment Share on other sites More sharing options...
Bobbsy Posted March 10, 2006 Share Posted March 10, 2006 Well, it's not so much physical contact between casings and wall boxes etc., though avoiding this can be useful. The thing about an unbalanced circuit is that it is much more prone to pick up interference from nearby sources, such as mains cables running parallel to the intercom wiring, any dimmers close by, mobile phones, TV receivers, computers etc. A lot of noise on the Tecpro system (and Clearcom as well) can be reduced or eliminated by careful siting of your cable runs. Beyond that, as has already been recommended, make sure that you use good quality screened cable and that all the connectors are properly made off. Bob Link to comment Share on other sites More sharing options...
Tomo Posted March 10, 2006 Share Posted March 10, 2006 So could it be advisable to avoid contact from the metal casing of the connector to the metal wall boxes and railings etc?What Brian means is that the 'Shield' or 'Screen' in the cable should NOT be connected to the metal shell of any wall boxes or XLR connectors. It should only be connected to the pin in the connector - Pin 1. For a cans loop it's especially important because the shield is used for the 0v reference for both power and signal, which will essentially double the apparent level of any hum (added by the amplifier AND in the signal). Link to comment Share on other sites More sharing options...
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