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Watts Of Electricity Vs. Watts Of Sound


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I want to gauge whether I'm overloading a mains socket, by adding up all the bits plugged into my trailing 4-way extension. I understand the combined wattage shouldn't exceed 3100 watts (or thereabouts). However, it's not clear what power-wattage an amp will draw from the mains point - is it the same as the power it's kicking out (sound wise) and if not - then how do I find out either way?

Confused as always, Chris. :wacko:

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Amplifiers are, at best, around 80% efficient (depending on topology, some much less so), meaning that they will only ever put out 80% of the power they draw in....

 

BUT capacitor banks have a large part to play in burst power which is why you see some crazy peak power figures on modern amps that exceed what could realistically be drawn down the power cable.

 

Also, although your amp may be rated at 1000w per channel it is unlikely that you'll be playing sine waves all night at full power, so you won't ever draw 2400w with both sides of the amp running hard.

 

Modern music has a duty cycle of between 2/3rds and 3/4 peak power so even running flat out you'll be putting out (and therefore drawing) significantly less than the rated value. If you have an active system then the bass will work much harder than the mid tops too so you can allow for that.

 

We've run silly rigs off of single and double 13A sockets when required and they've been fine. We had 8 Funktion 1 F218's and 6 Res4's on MC2 amps running off a twin 13A socket last month no problem.

 

I'd say if you regularly run flat out with the amps then use a number about 2/3rds of the combined channel output at the impedance you're running to calculate how much you can plug in. this will undoubtedly give you some headroom but thats always safer.

 

Lights are another matter....

DIY plans and pro audio related technical discussions

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The design of the amp also plays a big part. The types with switchmode power supply tend to be more efficient, they store less energy internally and draw it directly from the mains as and when needed. This may be a factor where spurious tripping or fuse blowing is leading one to suspect too much load on one socket.

 

The energy used also depends heavily on the nature of the music and the speakers connected.

 

 

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To put it in perspective, the Void Infinite 8v2 is capable of doing 3800w per side at 2ohms. It has a digital readout on the front to indicate how many amps its pulling from the mains. People I know use this to see just how high they can get it as a form of racing...

 

In normal use with 4 18" bass cabs per side playing bass heavy music like DnB and dubstep they tend to tick over about 6-8amps which is a lot lower than the theoretical 33A at 230v that you might expect. Thats not to say that they don't get up into the 20's but thats being silly and certainly well in excess of what you're likely to do at a disco.

DIY plans and pro audio related technical discussions

www.speakerplans.com/forum

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