owen_mcauley Posted June 13, 2003 Share Posted June 13, 2003 Hi guys, not sure whether this should be in light or sound but I'll give it a go here. A few times now, I've hired par16's off a hire company, they have come with just a domestic style 12 transformer, presumably dimmable. The problem is that they interfere on balanced audio lines coming from any microphone onstage, (and on lavalier radio mics, not as prominent tho)! So when they dim any open mic channel starts making the pa resemble a very loud dimmer rack! ;) Would the fact that the most problematic mics are on the grand pianos, be of any relevance? (yes I did say pianos) Any clues/hints on what causes such interference? Thanks Owen Link to comment Share on other sites More sharing options...
Chris M Posted June 13, 2003 Share Posted June 13, 2003 Are the cable runs withing a few inches of each other, cause sound/mic cables and power cables shouldn't be run next to each other. If they are running next to each other, I imagine you must be able to get some kind of super insulated cable ;) Alternativley just make sure the cables are far away from the sound cables, I believe its okay for them to cross at 90 degrees, just not run parallel. Link to comment Share on other sites More sharing options...
Brian Posted June 13, 2003 Share Posted June 13, 2003 1. what mics have you got on the grands? 2. are you really sure that the transformers are dimmable? Link to comment Share on other sites More sharing options...
robloxley Posted June 13, 2003 Share Posted June 13, 2003 Are they electronic transformers? Link to comment Share on other sites More sharing options...
owen_mcauley Posted June 13, 2003 Author Share Posted June 13, 2003 Sennheiser E 604's on grands for a little reinforcement, (small venue) will check transformers when I go in for the show, Only cables running nearby are the mains feed to the transformer, running across each other at 90 degrees at one point. Unavoidable due to the lighting install design and position of orchestra. Transformers themselves about 5 meters away from microphones/stageboxes. Only two more shows left so no big issues, I don't think anybody else has noticed! Will let you know what I've found out. PS Will a non-electronic transformer create more problems ( I know the obvious problems with using it on a dimmable circuit) than using the correct electronic transformer? Owen Link to comment Share on other sites More sharing options...
Brian Posted June 13, 2003 Share Posted June 13, 2003 A non-electronic transformer does not like being dimmed. The sharp switching edges caused by the dimmers can cause the core to saturate and then all sorts of noise is generated. (Technical note: core saturation is exactly what it sounds like, it soaks up so much magnetism that it can't take any more). Dimmable ones can still saturate, they normally just have a larger core and windings so it doesn't happen so easily. Some electronic transformers aren't much better, they are after all nothing more than a power oscillator. Any noise generated will radiate from all the cables connected both the mains side and the LV side. Link to comment Share on other sites More sharing options...
owen_mcauley Posted June 13, 2003 Author Share Posted June 13, 2003 They were electronic transformers, and yes I do know the difference between them, just not their noise characteristics, many thanks for all your input. Will probably bring it up again when some fool hires them in for not artistic benefit again. Owen Link to comment Share on other sites More sharing options...
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