Who's Who Posted October 8, 2012 Share Posted October 8, 2012 Bit of a query for anyone in the know. We played a gig last night in an old pub in the back end of Essex. The pub was a typical small oldie pub, wooden beams on the ceiling etc. We sound checked and my amp seemed really quiet. I changed all the leads and it still sounded much quieter than usual. Then when we came on to start the first set it was back up to it's usual volume. Everything was fine and then a couple of songs in the volume started dipping again. This carried on through the whole set with the volume dipping every now and again. I'm really hoping it's not a fault with my amp or cab and I won't get a chance to try it again till the end of the week. So I was hoping that such an old building, with equally old electrics, may cause this problem. Baring in mind a 4-piece band would be drawing a massive amount of electricity compared to the old T.V in the corner, is there a possibility that this was the cause of the problem. Is it possible that dodgy electrics could have caused this problem??? Thanks in advance guys Quote Link to comment Share on other sites More sharing options...
pietruszka Posted October 8, 2012 Share Posted October 8, 2012 I personally can't help you, but I will be following this thread. My PA (RCF 310A's and a Xenyx 2442 desk) seems to pick up static noise from somewhere and goes when the RCF's are turned off then on again. I wondered if it was the electrics to. Does your amp do this anywhere else? If it's fine everywhere else I'd assume it was the venue electrics. Hopefully someone will come along and explain things! Dan Quote Link to comment Share on other sites More sharing options...
Who's Who Posted October 8, 2012 Author Share Posted October 8, 2012 [quote name='pietruszka' timestamp='1349721796' post='1829663'] I personally can't help you, but I will be following this thread. My PA (RCF 310A's and a Xenyx 2442 desk) seems to pick up static noise from somewhere and goes when the RCF's are turned off then on again. I wondered if it was the electrics to. Does your amp do this anywhere else? If it's fine everywhere else I'd assume it was the venue electrics. Hopefully someone will come along and explain things! Dan [/quote] I've never had a problem with the amp before. But I wasn't sure if it had just started developing problems or if the electrics were causing it. Quote Link to comment Share on other sites More sharing options...
flyfisher Posted October 8, 2012 Share Posted October 8, 2012 I reckon you're clutching at straws regarding 'dodgy electrics'. UK mains voltage is very well regulated and things like voltage drops are very rare, so 'dodgy electrics' is likely to be mean faulty venue wiring but even then there are limited faults that will occur. Typical things like a missing earth connection or reversed live/neutral might be dangerous but are unlikely to cause your amp to behave as you described. I'd suggest you give your amp a workout at home or a rehearsal studio where you can rely on the mains supply and check if it is still playing up. Quote Link to comment Share on other sites More sharing options...
brensabre79 Posted October 9, 2012 Share Posted October 9, 2012 We often get this phenomenon in pub gigs where we all have to run off one manky old socket or something. I think it has to do with the amount of watts being drawn through a single socket, theres only so many available. I'm not talking the output watts of your amp but the required watts to run the various bits of equipment the band is using. Add all the amps, PA, outboard, lights etc. and you'll quickly get to the limit of power that one socket can provide. That's when amps start buzzing or acting up and generally underperforming - especially the ones with valves. ...on the other hand it could be that your amp is fu***d, so I would test it out at a practice or something. Quote Link to comment Share on other sites More sharing options...
flyfisher Posted October 9, 2012 Share Posted October 9, 2012 Often? There's certainly a limit to the number of watts that can be obtained from a single mains socket (about 3000 in fact) but when you get to that limit things won't start 'acting up' - in fact, things will just stop working when the fuse blows. If the electrics are so dodgy that someone has replaced the main fuse with a big nail then things will continue working normally until the overloaded wiring melts or starts a fire. I suppose it's possible that poor wiring could result in a significant voltage drop, which might cause problems, but I've done outdoor gigs with a six-piece band all powered from a single mains socket on the end of a 40m extension lead with no problems at all, hence my doubts about 'dodgy electrics'. Quote Link to comment Share on other sites More sharing options...
Musky Posted October 9, 2012 Share Posted October 9, 2012 It could be a supply problem (old, rural pub) or it could be a problem with their own electrics (in which case the place would be a fire hazard), but in both those scenarios I'd expect it to affect the whole band as well as the lighting (which would be very noticeable to everyone in the pub). So it's more likely to be the amp. I couldn't begin to guess all the possible causes but have experienced a similar problem with a dirty input socket. It would help if you could try to replicate the problem at home/rehearsal. Quote Link to comment Share on other sites More sharing options...
Who's Who Posted October 10, 2012 Author Share Posted October 10, 2012 Used the amp last night with no issues at all. Used all the same cables and the same bass and tried it at different voice levels, different settings, pick, fingers and had no issues at all. I had a spare valve with me ready to swap over hoping it may be a simple issue like that, but there was no need in the end. The amp worked fine all night. On the night in question we had my amp, the guitarist amp and his pedal board all running off an extension lead from single socket. Can't think what the problem was if it wasn't the electric as the amp was fine last night. Quote Link to comment Share on other sites More sharing options...
flyfisher Posted October 10, 2012 Share Posted October 10, 2012 Curious! Bad connection somewhere within the amp perhaps? I'm not saying it [u]couldn't[/u] be 'dodgy' mains supply but it still wouldn't bet on it. Reproducing the problem is usually the key to solving it. I always use one of these little gadgets at a new venue to verify that the mains socket I'm using is at least wired correctly: http://www.maplin.co.uk/mains-socket-tester-9800 I've also got one of these, which will measure the mains voltage and current being drawn: http://www.maplin.co.uk/plug-in-mains-power-and-energy-monitor-38343 These two devices should reveal any significant problems with the mains power supply and are generally useful things to have for peace of mind. Incidentally, I once had a problem with my Ampeg combo briefly cutting out with all the signs of an intermittent connection somewhere. I opened it up and, sure enough, the PCB trace to one of the large resistors in the power circuitry had cracked and come away from the board and was only being held in place by the resistor leg. Vibration was causing the contact to be unreliable, hence the cutting out. Obviously I can't tell if this is the sort of problem with your amp, but it's an example of what can happen with bass amps and - I'd say - is probably more likely than a faulty mains supply. Good luck with a solution though - I imagine it is very frustrating! Quote Link to comment Share on other sites More sharing options...
pietruszka Posted October 10, 2012 Share Posted October 10, 2012 Good to hear it's ok! I'm using my PA on Friday, I'm hoping I don't get any interference like I have done. FlyFisher, those items from Maplins look very worth while. I think a visit is in order! Dan Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted October 10, 2012 Share Posted October 10, 2012 If you have high-current devices being switched on, all plugged into the same socket as your amp, you can get a phenomenon known as 'brown-out' (cue the usual hilarity) where the mains voltage sags for a second or so. This can cause weird things to happen (such as digital kit resetting itself to default mode), but there should be no permanent damage. It used to happen to my guitar synth (cue more hilarity) when the singer switched all the stage light on using his foot on the rocker switch of a 4-way cable - very annoying! Quote Link to comment Share on other sites More sharing options...
Ghost_Bass Posted October 10, 2012 Share Posted October 10, 2012 I would bet on a faulty or tired valve starting to act up... maybe the vibration in the car on the way home set it back to a stable condition... i would go and get my amp checked just in case. Quote Link to comment Share on other sites More sharing options...
Big_Stu Posted October 10, 2012 Share Posted October 10, 2012 I had it once on my valve amp; it was a pre-amp valve letting me know that it was about to go to the great Woodstock gig in the sky. Quote Link to comment Share on other sites More sharing options...
gjones Posted October 10, 2012 Share Posted October 10, 2012 I was playing a gig last week where the electricity was provided from a generator. I noticed that the lights were flickering on and off and my MiBass head was as well. Strangely, the guitarists valve amp wasn't affected and neither was the vocal PA. It pissed me off mightily (as I was worried about damage that might be caused to my amp) and was very close to switching my amp off and walking off stage. Quote Link to comment Share on other sites More sharing options...
thinman Posted October 11, 2012 Share Posted October 11, 2012 In my job I get to see the mains voltages at various diverse locations in the UK and have seen the AC RMS voltage vary from 215v to 250v - that's a variation of 15%. Those levels can follow an expected time of day pattern, i.e. the voltage can drop during the ads in Corrie when everyone puts the kettle on and there are many short term effects, e.g. a nearby industrial user switching something on or off. So although the generated voltage may be well regulated, local cable lengths/capacities and usage can have a marked local effect. That variation in AC voltage can feed through to the power rails in your power amp as they are proportional based on the transformer. Say at full output into 8 ohms your amp outputs 50v (with 250v in ) (OK - I'm fudging this here as rail voltage is usually derived from the peak rather than RMS but the principle is the same). 50/8 = 6.25A, if the rail voltage is 15% lower (50*.85)/8 = 5.3A Power is I[sup]2[/sup]R then the difference in max power output = 225W vs 312W - probably noticeable as the overall gain would be lower. I've probably made some horrific error here but I'm sure someone will gleefully point it out! Quote Link to comment Share on other sites More sharing options...
flyfisher Posted October 11, 2012 Share Posted October 11, 2012 Mains voltage variations might affect the DC power rails in old designs without stabilised PSUs, but I'd hope that more modern stabilised PSU designs would adjust for variations in mains input voltages. Also, the nominal mains voltage is 230Vac, +10% and -6% or a range of 216-253 Vac, so any amp (or other device) that can't cope with such variation could be argued to be unfit for purpose. Quote Link to comment Share on other sites More sharing options...
Who's Who Posted October 14, 2012 Author Share Posted October 14, 2012 Gigged the amp last night and it wad absolutely fine. That's a studio practice and a gig now where there hasn't been any issues, I'm convinced it was a power/electrics issue in that last pub. Anyway, I'm gonna stick a new valve in it just for peace of mind, but fingers crossed I may now be sorted. Thanks for all the advice guys Quote Link to comment Share on other sites More sharing options...
flyfisher Posted October 14, 2012 Share Posted October 14, 2012 Glad to hear it hasn't been playing up recently. Nothing worse than worrying about unreliable gear. It would be very interesting to take the amp back to the 'problem' pub and try again, though I realise that's probably impractical. Quote Link to comment Share on other sites More sharing options...
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