# So how much power do you really need?



## Talley (Dec 8, 2010)

Decided to take a few photos powering up my equipment from idle to full on and I also have a small video of the amps bouncing around. Ran the Fluke 289 in min/max mode since it's captures data at 250 micro seconds of resolution and played a movie (Fury - 4 tanks vs 1 scene) and this is the result I got:

THIS ENTIRE TEST WAS RAN AT -10DB VOLUME

https://www.youtube.com/watch?v=muC_kcfx4OA&feature=youtu.be



everything off I was only pushing .8amp = 100w
turned the XPA-7 amp on and my inrush went to 6.7A and settled around 3.7A with just the amp on idling and everything else off idling so about 3 amps or about 370W just for the amp
turned on projector, xmc-1, subwoofer & bluray and idling without anything playing went to 4.7A which means another 120W was added 
So "Peak" power needs was pushing 22A

Obviously everyones needs are different and you can see my equipment in my signature but it gives you some idea that TWO 20A circuits would be enough to fill most anyones needs who shares a single multichannel amp. My future plans is to add two XPA-1 for the mains and let the xpa-7 run the surrounds so this would obviously absorb more and adding a second subwoofer will no doubt absorb more.

The interesting and obvious thing about the video is the peak came during the loud tank parts that included the main gun firing and when the motor would rev up and really push the sub into playing mode. "Most" of the time the amps was only around 7-9a.

Just figured I'd share for those who might be curious. I suppose me having 80 amps worth of 120v on my main with the 9 20a circuits is a tad overkill. Even adding a second subwoofer and two xpa-1s and maybe a couple height speakers I don't see me ever pushing past 30-35 amps and this is PEAK power... sustained would be less than 20 for sure.


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## Talley (Dec 8, 2010)

The bigger question is:

What would be the peak draw if I ran my system at 0db?


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## Owen Bartley (Oct 18, 2006)

That's great info Talley, thanks for posting. I've often wondered how many breakers I'd (theoretically) need when I finally get to building. Maybe a dedicated line for sub amps and 1 or 2 more for assorted other gear at most.


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## Talley (Dec 8, 2010)

I would say each sub get a circuit and the amp get its own then everything else can be on one. 

It's also known that even at peaks of 22 amps the breaker will not trip. They will push beyond that for short peaks. I would say my entire system was really around 10amps. Again two circuits would cover 95% of people.


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## willis7469 (Jan 31, 2014)

Thanks talley. Nice to see a real world case study. 


Sent from my iPhone using Tapatalk


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## Talley (Dec 8, 2010)

willis7469 said:


> Thanks talley. Nice to see a real world case study.
> 
> 
> Sent from my iPhone using Tapatalk


No problem. even a SINGLE 20 amp circuit would probably cover 95% and TWO 20 amp circuits would cover the remaining 4.5% and then you have the .5%ers who would need more.

Case in point... Plan ahead if you can and always size your feeders large. #8 would be great #6 even better.


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## B- one (Jan 13, 2013)

Very interesting,I have often wondered if I would have enough power as I add stuff and have been lucky so far! I did tell the electrician do what you need to!


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## Savjac (Apr 17, 2008)

Thanks Talley, while I may not exceed the limits for my man cave, I now think it proper to add another dedicated circuit.
This should be fun....


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## chashint (Jan 12, 2011)

All the photos indicate the meter is displaying milli-amps.
Is there some kind of scaling going on ?


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## Talley (Dec 8, 2010)

chashint said:


> All the photos indicate the meter is displaying milli-amps.
> Is there some kind of scaling going on ?


1000:1

It's how the Fluke i400 works with the multimeters. Most scale the same way.

here is the manual just in case you were wondering http://media.fluke.com/documents/i400____iseng0000.pdf

Page 2 figure 1 puts it into perspective.


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## chashint (Jan 12, 2011)

Talley said:


> 1000:1 It's how the Fluke i400 works with the multimeters. Most scale the same way. here is the manual just in case you were wondering http://media.fluke.com/documents/i400____iseng0000.pdf Page 2 figure 1 puts it into perspective.


Got it, the clamp on probe was not mentioned earlier.
Since you have the clamp on, what kind of readings can you get at one of the front main speaker terminals ?


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## Talley (Dec 8, 2010)

chashint said:


> Got it, the clamp on probe was not mentioned earlier.
> Since you have the clamp on, what kind of readings can you get at one of the front main speaker terminals ?


this clamp on becomes unreliable under a half amp or about 45w in speaker terminology. I have a ground resistance clamp on meter that is super sensitive with .01ma resolution that I could use and watch but nothing I could record.

Is there any particular reason to test the speaker circuit?


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## chashint (Jan 12, 2011)

Just curious what kind of current is going through the speaker.
Without the voltage measurement I guess it really is not very useful for anything.
You have been working hard on your system, much harder than I am willing to work on something like this.
I am glad you are beating it into submission.


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## Talley (Dec 8, 2010)

chashint said:


> Just curious what kind of current is going through the speaker.
> Without the voltage measurement I guess it really is not very useful for anything.
> You have been working hard on your system, much harder than I am willing to work on something like this.
> I am glad you are beating it into submission.


As an electrician you are taught to troubleshoot starting at the source first then work your way to the device. My first goal was to get my equipment acquired and setup and then work on the rest. So now I'm going back to the source and starting over and I want every detail as perfect as I can get it.

I've got some changes coming up that will be interesting at least on the power side and then I will work on moving toward the source.


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## Tonto (Jun 30, 2007)

Tally, it's great to have you on board!

That is really a pertinent study that we can all benefit from. Keep up the good work.


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