Happy Jack Posted September 16, 2012 Share Posted September 16, 2012 In matters electrical, I am a complete ignoramus who leaves things plugged in so as to avoid having electricity trickling out of the socket and ruining the carpets. I really, [i][b]really [/b][/i]do not get the whole volts / amps / watts thing, but I have a simple (I hope) question. I nearly supplied the PA for a disco rig for a big party. It's gone away now, but the question remains. Imagine the following:[list] [*]Disco mixer/desk into my band PA desk; [*]PA desk #1 into a 500W power amp, driving 2 x 12" tops at 8 Ohms each; [*]PA desk #2 into a 1000W power amp, driving 2 x Barefaced cabs at 4 Ohms each. [/list] Can all that be driven with a single 13A plug? Quote Link to comment Share on other sites More sharing options...
flyfisher Posted September 16, 2012 Share Posted September 16, 2012 (edited) Yes. Probably. A 13A socket can provide, er, 13 amps at 240 volts (it varies a bit, but that'll do for this example). Multiply those two numbers together and you get 3120, which is also the number of watts of energy available. Looking at the PA example, you have 1500 watts of amplification. This is the OUTPUT power of the amplifiers. If the amplifiers were 100% efficient at turning the mains input power into output power then they would also consume 1500W from the mains socket - which is well within the 3120 watts available. But amplifiers (or anything else) are not 100% efficient when converting one form of energy (e.g. electricity) into another form of energy (e.g. sound) and the wasted energy usually ends up as heat, meaning that MORE energy goes INTO the amplifier that comes OUT of it. So, the amplifiers will require MORE that 1500 watts from the mains socket. The key question is how much more? This is determined by the efficiency of the amplifier, which is an unknown (at this stage anyway). But, let's be pessimistic and assume that the amplifiers are only 50% efficient. This means they'll only turn HALF of the mains power into sound power. We know they produce 1500W of sound power, so if that is only HALF of the mains power it means that they would need 3000 watts of mains power. 3000 watts is still less than the 3120 watts that the mains socket can provide so a single plug will be adequate. Hence my first answer of 'yes'. My second answer of 'probably' is because I don't know the efficiency of the amplifier for certain so I'm making a guess. There are other considerations such as the volume levels involved, but the above numbers assume the worst case (except the amplifier efficiency guess). If you really want to be sure then you could buy a power consumption meter from the likes of Maplin ([url="http://www.maplin.co.uk/plug-in-mains-power-and-energy-monitor-38343"]http://www.maplin.co...y-monitor-38343[/url]) and check the actual power consumption (from which you could then work out the amplifier efficiency if you were geeky enough ). Otherwise, just plug them in and give it a go. The worst that will happen is a blown fuse - assuming that everything is correctly fused in the first place! Edit: just noticed I've only allowed for the amplifiers and not the mixers etc. These require relatively little power but they are likely to be a bit over the 120 watts that are remaining after my 50% amplifier efficiency example. However, 50% efficiency is pretty low and I'd expect it to be higher than this so I'll stick by my 'yes, probably' answer. If you're really worried about a fuse blowing mid-gig then I'd recommend the power meter to check what sort of 'headroom' you have in terms of mains power consumption. Otherwise, it is always a good idea to split such loads across more than one mains socket - even if they are on the same circuit, because the mains circuit will be able to supply 30 amps or 7200 watts. Edited September 16, 2012 by flyfisher Quote Link to comment Share on other sites More sharing options...
BOD2 Posted September 16, 2012 Share Posted September 16, 2012 Yes ! Quote Link to comment Share on other sites More sharing options...
Happy Jack Posted September 16, 2012 Author Share Posted September 16, 2012 Thanks guys. Quote Link to comment Share on other sites More sharing options...
mart Posted September 16, 2012 Share Posted September 16, 2012 I reckon flyfisher's answer must rate as one of the most comprehensive (and correct ) answers that I've seen in basschat, and that includes some pretty stiff competition! Quote Link to comment Share on other sites More sharing options...
flyfisher Posted September 16, 2012 Share Posted September 16, 2012 (edited) [blush] Just trying to give back a little in return for all the stuff I've learned from BC, but thanks for the kind words. Edited September 16, 2012 by flyfisher Quote Link to comment Share on other sites More sharing options...
bertbass Posted September 17, 2012 Share Posted September 17, 2012 The fuse in the plug is 13 amps, the ring main that it's connected too is 32 amps. Any problems use another socket as well. Quote Link to comment Share on other sites More sharing options...
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