Happy Jack Posted January 22 Share Posted January 22 The Junkyard Dogs set up at a big Social Club on Saturday night, large hall and a very nice stage but audience a bit thin on the ground - it was the third week of January, the temperature had barely risen above zero for three days, and it was the band's first gig at that venue. No matter, treat it as a combined audition for future gigs and well-paid rehearsal. Which we bloody needed, I can tell you. Powered subs on each side of the stage driving passive tops, 13A sockets under metal flaps across the front of the stage so no messy cabling, everything is set up so it's time to switch it all on. Stage Left sub is fine, exactly as usual; Stage Right sub produces an enormous hum. Play music through the system and Left is just fine, Right is very, very faint ... lots of hum, very little music. Hmmmmmm. Literally. It sounds a lot like a ground loop so flick the Phase switch on Stage Right. Nada. Not a sausage. Bugger all. The hum is still there. Replace the XLR cable from PA to Stage Right. No change, the hum is still there. Switch the Main Out L/R cables at the PA. The hum stays with the Stage Right unit and doesn't shift to the Left. Switch off Stage Right and unplug everything. Count slowly to five. Plug it all back together and switch on. The hum is still there and the clock is ticking. Out Of Time. Game Over. Insert New Coin. Switch off Stage Right and unplug everything, then run a long Speakon cable from the Stage Left passive top to the Stage Right passive top. It works perfectly; we now have the entire PA being driven by the Stage Left powered sub. Play gig, load out, go home, go to sleep. Quote Link to comment Share on other sites More sharing options...
Happy Jack Posted January 22 Author Share Posted January 22 While I'm asleep, I dream about the gig. I was looking around as I played and noticed that - as with many Clubs I have played - it's very obvious that much of the decor has been cobbled together on the cheap, presumably by Members volunteering to help. In my dream I was fixated on this poor-quality work. Wake up, get out of bed, down to the studio and plug the whole f***ing PA together but I know what's going to happen. Sure enough, everything works just fine. I'll lay you odds of 100-1 that if you plugged a tester into the socket we used for the Stage Right sub it would have shown a fault ... seriously defective wiring at that point. It was the one thing we didn't isolate (well you don't, do you?) and - even more irritating - two of the four of us there actually had testers in our bags. 🙄 Quote Link to comment Share on other sites More sharing options...
Beedster Posted January 22 Share Posted January 22 A cautionary tale Jack, dodgy venue electrics can do a whole lot worse stuff to you than lower your spls 👍 1 Quote Link to comment Share on other sites More sharing options...
Huge Hands Posted January 22 Share Posted January 22 If you had have plugged in your tester, it may have shown a fault, or it may not. In large venues the sockets can often be wired to different distribution boards or even electrical phases, so you can end up with all sorts of ground loops or weird issues. You could have even been plugging into a lighting dimmer circuit if some in-house techy type had rewired it so! Sounds like you did the perfect work around to me, and glad your kit seems to have come out of it unscathed! 1 Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted January 22 Share Posted January 22 (edited) Or there's a loose wire in your sub. Edited January 23 by Downunderwonder Ninja correction. 1 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted January 23 Share Posted January 23 22 hours ago, Happy Jack said: While I'm asleep, I dream about the gig. I was looking around as I played and noticed that - as with many Clubs I have played - it's very obvious that much of the decor has been cobbled together on the cheap, presumably by Members volunteering to help. In my dream I was fixated on this poor-quality work. Wake up, get out of bed, down to the studio and plug the whole f***ing PA together but I know what's going to happen. Sure enough, everything works just fine. I'll lay you odds of 100-1 that if you plugged a tester into the socket we used for the Stage Right sub it would have shown a fault ... seriously defective wiring at that point. It was the one thing we didn't isolate (well you don't, do you?) and - even more irritating - two of the four of us there actually had testers in our bags. 🙄 I have a long lead with several sockets at 1 metre intervals. I lay it across the back of the stage and everything, including the PA, is run from it. It is rated at 13 amps and that gives us a limit of just over 2900* watts, but we rarely use the big PA and even that is within limits. It avoids this type of problem. *Calculated at 230V ac. In most places the UK voltage is still around, or above 240V ac. so clsoefr to 3100 watts. Quote Link to comment Share on other sites More sharing options...
Happy Jack Posted January 23 Author Share Posted January 23 32 minutes ago, Chienmortbb said: I have a long lead with several sockets at 1 metre intervals. I lay it across the back of the stage and everything, including the PA, is run from it. It is rated at 13 amps and that gives us a limit of just over 2900* watts, but we rarely use the big PA and even that is within limits. It avoids this type of problem. *Calculated at 230V ac. In most places the UK voltage is still around, or above 240V ac. so clsoefr to 3100 watts. We have the same leads ... two of them. In fact, I remember when a Basschatter first discovered them on special at Lidl in "the middle aisle" and posted about them. We nearly lost long-standing members in the rush to get them. 🤣 The problem here was that we had those leads at the back of the stage (for backline & lighting etc.) but we were using the stageboxes - if that's the correct description - to power things at the front of the stage. Quote Link to comment Share on other sites More sharing options...
Paul S Posted January 23 Share Posted January 23 52 minutes ago, Happy Jack said: We have the same leads ... two of them. In fact, I remember when a Basschatter first discovered them on special at Lidl in "the middle aisle" and posted about them. We nearly lost long-standing members in the rush to get them. 🤣 ... and the damned things haven't been in stock since. Quote Link to comment Share on other sites More sharing options...
Happy Jack Posted January 23 Author Share Posted January 23 Yup. Basschatters bought the lot. 🙄 Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted January 24 Share Posted January 24 Guilty as charged your honour. I am Lidl's secret shopper Anyway I deliberately choose to run everything off a single socket. The theory is to have everything connected to the same earth point. Any resistance in the wiring can lead to differences in earth potential and voltages appearing across betwen gear plugged into different sockets. I measured 47volts between earths once, after I got a belt off the mic of course. I re-wired some 6-way mains strips so I have two with 5m leads and one with a 10m lead and Ihave one with the bought 2m lead. First thing I do at every set up is to plucg in to the most convenient socket and run the cables so there is a 6-way at each corner of the stage. Everyone plugs into these and I won't say its idiot proof but it reduces the chance of miss hap. As John says you've got nearly 3kW to play with and that your PA is probably running at 20% load anyway. With LED lighting most of us could run off a 5A fuse never mind 13A 1 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted January 24 Share Posted January 24 3 hours ago, Phil Starr said: Anyway I deliberately choose to run everything off a single socket. The theory is to have everything connected to the same earth point. This was my reasoning too. Quote Link to comment Share on other sites More sharing options...
Suburban Man Posted February 4 Share Posted February 4 On 24/01/2024 at 20:16, Chienmortbb said: This was my reasoning too. On 24/01/2024 at 15:35, Phil Starr said: Guilty as charged your honour. I am Lidl's secret shopper Anyway I deliberately choose to run everything off a single socket. The theory is to have everything connected to the same earth point. Any resistance in the wiring can lead to differences in earth potential and voltages appearing across betwen gear plugged into different sockets. I measured 47volts between earths once, after I got a belt off the mic of course. I re-wired some 6-way mains strips so I have two with 5m leads and one with a 10m lead and Ihave one with the bought 2m lead. First thing I do at every set up is to plucg in to the most convenient socket and run the cables so there is a 6-way at each corner of the stage. Everyone plugs into these and I won't say its idiot proof but it reduces the chance of miss hap. As John says you've got nearly 3kW to play with and that your PA is probably running at 20% load anyway. With LED lighting most of us could run off a 5A fuse never mind 13A Running off a single socket also prevents the accidental use of separate phases. The installation (venue, hall, whatever) will regularly have 3-Phase power incoming and a number of power sockets on each phase intended to balance the overall load. Obvs only an idiot would leave different phases close to each other on stage... but stranger things have been known. 2 Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted February 4 Share Posted February 4 Having different phases isn't a real issue. Having outlets with different ground potentials is. If correctly wired you don't see that, but wherever electricity exists Murphy's Law is in full effect. Quote Link to comment Share on other sites More sharing options...
Suburban Man Posted February 4 Share Posted February 4 3 hours ago, Bill Fitzmaurice said: Having different phases isn't a real issue. Having outlets with different ground potentials is. If correctly wired you don't see that, but wherever electricity exists Murphy's Law is in full effect. Well I wouldn't recommend it. 🙂 Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted February 5 Share Posted February 5 On 05/02/2024 at 04:22, Bill Fitzmaurice said: Having different phases isn't a real issue. Having outlets with different ground potentials is. If correctly wired you don't see that, but wherever electricity exists Murphy's Law is in full effect. It's why if you look up the phone book for an electrician you won't find any named Murphy. Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted February 5 Share Posted February 5 On 04/02/2024 at 19:07, Suburban Man said: Well I wouldn't recommend it. 🙂 No, the voltage between phases over here is over 400V. Quote Link to comment Share on other sites More sharing options...
tauzero Posted February 6 Share Posted February 6 21 hours ago, Chienmortbb said: No, the voltage between phases over here is over 400V. How would they come together? Socket A powers a few things, which will almost all contain some form of power supply converting the AC to DC. Socket B on a different phase powers various other devices to which the same applies. Are there any devices which will connect socket A to socket B? Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted February 6 Share Posted February 6 2 hours ago, tauzero said: How would they come together? Socket A powers a few things, which will almost all contain some form of power supply converting the AC to DC. Socket B on a different phase powers various other devices to which the same applies. Are there any devices which will connect socket A to socket B? They should not come together, and mains sockets on different phases should not be closer than can be touched simultaneously by a single person. Quote Link to comment Share on other sites More sharing options...
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