warnock Posted September 8, 2009 Share Posted September 8, 2009 Hey was doing a gig in a small theatre the other night using inhouse PA (Tanoy) and using Wharfedale EVP-X15M passive monitors that retail around £180 I think. Got a really nice sound from the monitors however there was a lot of interfearence from the lighting circuit I think. Whenever the lights got brighter the interfearence through the monitors would increase. It sounded like a loud buzzing noise. Is there anyway of getting rid of this if I come across the same issue in the future? Link to comment Share on other sites More sharing options...
Wilflet Posted September 8, 2009 Share Posted September 8, 2009 we're you drawing off the same power as the lampys? Link to comment Share on other sites More sharing options...
warnock Posted September 8, 2009 Author Share Posted September 8, 2009 we're you drawing off the same power as the lampys? hey, no the sound equipment was all run off a seperate 32 amp circuit Link to comment Share on other sites More sharing options...
timtheenchanteruk Posted September 8, 2009 Share Posted September 8, 2009 where does it originate form though??we have 32 & 16A sockets around the theatre that all come from the lighting supply board, there are only a couple that come from the "dom3stic" supply side (ie no dimmers on the circuit). Link to comment Share on other sites More sharing options...
warnock Posted September 8, 2009 Author Share Posted September 8, 2009 where does it originate form though??we have 32 & 16A sockets around the theatre that all come from the lighting supply board, there are only a couple that come from the "dom3stic" supply side (ie no dimmers on the circuit). to be honest im not sure. the theatre technician said that use this 32amp power as you will get "clean" sound for the PA. Link to comment Share on other sites More sharing options...
Brian Posted September 8, 2009 Share Posted September 8, 2009 Don't get bogged down in the old 'sound should be on a different phase' debate - it makes no difference. A properly designed and maintained audio system doesn't care where its power comes from. You said that the monitors were passive? The ones I found with a google appear to be active (ie built in amps). If this is the case then I'd put money on you having an unbalanced audio connection feeding the monitors. [EDIT]****ing websites which use the wrong picture. So, the speakers you have are passive but how were you feeding them? My comments still stand. Link to comment Share on other sites More sharing options...
warnock Posted September 8, 2009 Author Share Posted September 8, 2009 Don't get bogged down in the old 'sound should be on a different phase' debate - it makes no difference. A properly designed and maintained audio system doesn't care where its power comes from. You said that the monitors were passive? The ones I found with a google appear to be active (ie built in amps). If this is the case then I'd put money on you having an unbalanced audio connection feeding the monitors. [EDIT]****ing websites which use the wrong picture. So, the speakers you have are passive but how were you feeding them? My comments still stand. cool.........I have the monitors connected as follows...... jack lead from aux1 and aux2 to input jacks on dbx 215 graphic. Then x2 XLR from outputs to input channels1 and 2 on amplifier. Then the cables from amp to each monitor. cheers Link to comment Share on other sites More sharing options...
MarkPAman Posted September 8, 2009 Share Posted September 8, 2009 jack lead from aux1 and aux2 to input jacks on dbx 215 graphic. If these are unbalanced leads (tip & screen only) then that's where I'd start looking. What desk is it? Link to comment Share on other sites More sharing options...
warnock Posted September 8, 2009 Author Share Posted September 8, 2009 jack lead from aux1 and aux2 to input jacks on dbx 215 graphic. If these are unbalanced leads (tip & screen only) then that's where I'd start looking. What desk is it? the desk is an Allen and Heath mixwizard wx 16:2 http://www.allen-heath.com/UK/DisplayProduct.asp?pview=49 I think it may be the cables that is the issue.... I will have a look at them Link to comment Share on other sites More sharing options...
KevinE Posted September 8, 2009 Share Posted September 8, 2009 Always worth exploring the 'source' of the noise as well, it's often easier to kill it here especially if it's caused by a fault of some sort. Link to comment Share on other sites More sharing options...
AndyL Posted September 8, 2009 Share Posted September 8, 2009 Don't get bogged down in the old 'sound should be on a different phase' debate - it makes no difference. A properly designed and maintained audio system doesn't care where its power comes from. So, the speakers you have are passive but how were you feeding them? My comments still stand. jack lead from aux1 and aux2 to input jacks on dbx 215 graphic. Then x2 XLR from outputs to input channels1 and 2 on amplifier. Then the cables from amp to each monitor. cheersAgree about the 'phase' red herring.... but earthing is another matter. Anyway, the connection from the graphic to the amp is XLR and therefore presumably meant to be balanced and shielded. But you don't say where the amp was in relation to the desk/graphic, i.e. how long were the XLR cables? All the sound power was from one place, but how was it distributed? Although the unbalanced jack leads are an understandable suspect in this investigation unless the are really looooooooong or faulty or very near the source of the interference they wouldn't necessarily be top of my list. From the description it sounds like a ground loop, and/or signal cables running (possibly unwittingly) parrallel to (hidden?) lighting supply cables. Link to comment Share on other sites More sharing options...
rob098 Posted September 9, 2009 Share Posted September 9, 2009 jack lead from aux1 and aux2 to input jacks on dbx 215 graphic. If these are unbalanced leads (tip & screen only) then that's where I'd start looking. What desk is it? the desk is an Allen and Heath mixwizard wx 16:2 http://www.allen-heath.com/UK/DisplayProduct.asp?pview=49 I think it may be the cables that is the issue.... I will have a look at them I've got both these products and had a similar issue. The Mixwiz outputs balanced and the DBX inputs balanced.Make sure you use stereo to stereo screened jack cable for balanced audio connection.As indicated, this may not be the root of the problem, but you should be running balanced wherever possible. At the risk of hijacking this thread - its also worth checking with that desk if your auxes are running pre or post EQ.A&H tend to ship MixWiz pre EQ for monitors which, depending on your preference, may not be very desirable. This wont help you with your interference issues however! Link to comment Share on other sites More sharing options...
paulears Posted September 9, 2009 Share Posted September 9, 2009 My own venue has pretty ancient dimmers but many visitors like to use the 3 phase supply in a more convenient place - SL, as it happens, when our sound dedicate power is SR. Even with our nearly 40 year old dimmers chopping up the mains from the busbars rather close, it's always resulted in very rare problems, with most people finding it very quiet and hum free, even when the dimmers are on half. We discovered a big problem recently though, when somebody wanted to use the 13 amp ring main in the dressing rooms - there are a few dotted around that are normally enough, but there is a separate ring for freestanding heaters - because when it gets cold on the end of a pier, it's really cold. People then bring in fan heaters and hence the extra ring. Somebody wanted it on, so I flipped the big lever in the intake room, and every guitar amp on stage hummed. Turn it off again, and silence returned. Working method for that show - heat on the loud numbers, off for the chat, and off for the ballads where the hum would be obvious. The hum did also change in tone during dims, but how on earth a ring main that runs from the main intake room, not from any supply on or near the stage can produce this weirdness is beyond me! Anyone care to have a stab in the dark? Link to comment Share on other sites More sharing options...
Brian Posted September 9, 2009 Share Posted September 9, 2009 Anyone care to have a stab in the dark?Difficult to know without knowing how the whole lot is wired but I'd go for a N-E fault somewhere. Link to comment Share on other sites More sharing options...
dbuckley Posted September 10, 2009 Share Posted September 10, 2009 Along with what Brian suggested, there may be a cross-connection on a neutral, quite a common feature on bad wiring (even by "professional" electricians) such that the route out and back tothe loads is not the same. Thus you get an inductive effect, which could be what the amps are picking up on. If you were in NZ I'd be down there with my test equipment, as that is indeed an interesting "feature"... Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.