gnomatron Posted November 19, 2015 Share Posted November 19, 2015 hi! Experienced an odd issue the other day. We had a buzz in a conference room, which we traced back to the dimmers - they're strand LD90s and a bit long in the tooth, no huge surprise there. The rack itself is buzzing more than I'd normally expect, and seems to be causing a buzz in the PA. Now, this is where it gets a bit puzzling - even with both FOH rig and public address system in the room muted at the amplifiers there's still a noticeable buzz in the room itself. I know lanterns buzz audibly but has any experienced them doing so loudly enough to be heard from ground level 4 metres or so away? We couldn't get ladder etc. in to have a listen closer but even with all conceivable noise sources in the room muted there was no likely source of the noise other than the lanterns (source 4s) in the room. Link to comment Share on other sites More sharing options...
timsabre Posted November 19, 2015 Share Posted November 19, 2015 Yes, you can get quite a loud noise from the lamp filaments. This would normally change with the dim level, falling to nothing at full brightness.LD90's are a relatively new dimmer design. Install dimmers have a long life. Is there something odd plugged into them like a load of 12V lighting transformers or anything? That can make them buzz more. Link to comment Share on other sites More sharing options...
TomHoward Posted November 19, 2015 Share Posted November 19, 2015 What lanterns are they? Par cans seem to buzz a lot. Other lanterns with T class lamps or similar seem to buzz less. Link to comment Share on other sites More sharing options...
Junior8 Posted November 19, 2015 Share Posted November 19, 2015 Yes certainly I have heard them from this distance especially at certain check levels. Link to comment Share on other sites More sharing options...
Srobo512 Posted November 19, 2015 Share Posted November 19, 2015 I've also had this. Especially with blinders Sam Link to comment Share on other sites More sharing options...
gnomatron Posted November 19, 2015 Author Share Posted November 19, 2015 Ok, cheers. I should have said, I have heard buzzing like this before, but mostly with par lamps. The lamps are all varieties of source 4, and while I've heard them buzz a little never loud enough to be heard more than a couple of feet away. As far as I know there's nothing odd plugged into the dimmers, just source 4 profiles and parnels. The buzz does disappear at 100%. Link to comment Share on other sites More sharing options...
alistermorton Posted November 19, 2015 Share Posted November 19, 2015 Could it be sometihng as simple as a recent refocus has changed the positions of the lanterns (and hence the lamps in them) and made the buzzing more noticeable? I've noticed PAR cans seem to buzz differently depending on orientation. Link to comment Share on other sites More sharing options...
musht Posted November 19, 2015 Share Posted November 19, 2015 Flash through them at 50% see if can isolate it to a single problem lantern? Link to comment Share on other sites More sharing options...
timsabre Posted November 19, 2015 Share Posted November 19, 2015 Also what is the history of this problem? Is this a venue you know well where the problem has just started, or could it have been like this for a while? I do know of one place wired in singles in metal trunking where the wiring buzzes audibly as the wiring vibrates slightly in the trunking. Link to comment Share on other sites More sharing options...
DrV Posted November 19, 2015 Share Posted November 19, 2015 LD90's are a relatively new dimmer design. (My emphasis) Tim, is that a typo or am I missing the point? Dave Link to comment Share on other sites More sharing options...
timsabre Posted November 19, 2015 Share Posted November 19, 2015 LD90's are a relatively new dimmer design. (My emphasis)Tim, is that a typo or am I missing the point? I meant in terms of the design, they are relatively new digital based dimmers, i.e. probably under 20 years, dimmer technology has not really moved on significantly since then apart from IGBT dimmers. Many places I go to have older dimmers than that, if they were Permus or JTM's or something I could understand if there were mystery buzzing problems. Link to comment Share on other sites More sharing options...
DrV Posted November 19, 2015 Share Posted November 19, 2015 LD90's are a relatively new dimmer design. (My emphasis)Tim, is that a typo or am I missing the point? I meant in terms of the design, they are relatively new digital based dimmers, i.e. probably under 20 years, dimmer technology has not really moved on significantly since then apart from IGBT dimmers. Many places I go to have older dimmers than that, if they were Permus or JTM's or something I could understand if there were mystery buzzing problems. At the risk of wandering too far OT, I can see that the method of triggering is different - the older units using a conventional ramp generator whereas the LD90 times everything digitally, but in terms of the power end, one uses two thyristors whereas the other uses a triac, which is almost the same thing. They both use iron cored chokes rather than the more modern ferrite ring cores but would you consider that there is any other key difference between them which would make one "new"er than the other. (This is a genuine question - I'm not attempting point scoring of any sort!) Dave Link to comment Share on other sites More sharing options...
timsabre Posted November 19, 2015 Share Posted November 19, 2015 I was mainly thinking of interference suppression (smooth the switching edges wot cause the buzzing) which has become more effective in newer designs as EMC standards have been tightened. Maybe I'm just getting old, thinking of a 20 year old dimmer system as relatively new. But I still come across loads of Mk1 betapacks and Zero88 stuff of a similar vintage. Link to comment Share on other sites More sharing options...
DrV Posted November 19, 2015 Share Posted November 19, 2015 Fair enough! I have repaired some STMs, PIPs, Betapack1s and very old Act 6s together with LD90 processors recently so I'm wondering about an archaeology degree as the next step. Compared with the first 4 the LD90 is indeed a modern, sophisticated design!!! Not like the salt pots at Ally Pally though... :) Dave Link to comment Share on other sites More sharing options...
Bryson Posted November 19, 2015 Share Posted November 19, 2015 Filament sing is worst at around 30%, so if it's a chronic problem, you could consider lamping down (eg: run a 575W or 375W lamp version instead of a 750W) and running at a higher level. Link to comment Share on other sites More sharing options...
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