Calculate an amps efficiency
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=50857
Printed Date: May 15, 2025 at 11:31 AM
Topic: Calculate an amps efficiency
Posted By: skoldspuppy
Subject: Calculate an amps efficiency
Date Posted: February 25, 2005 at 6:10 PM
Hi all, Is there a mathematical way to calculate an amps effciency
I thought its was input divided by ouput times 100
Any ideas? Later
Skold ------------- 2004 Honda Civic Ex 4Dr
Kenwood DDX-7015/W Nav
4 Fosgate T152C
Hifonics Brutus BX1500D
RE XXX 12 in a 4 Cube Snail Shell
Replies:
Posted By: haemphyst
Date Posted: February 25, 2005 at 9:20 PM
input voltage times input current = input watts
RMS output watts divided by input watts times 100 = efficiency
14.4 X 30 = 432 watts
300 / 425 = .694 X 100 = 69.4% efficiency
While this is a VAST oversimplification, this is pretty close, and will get you an efficiency number approaching the real numbers...
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: skoldspuppy
Date Posted: February 25, 2005 at 9:30 PM
Thanks, then in theory my new Memphis 16-MC500D is 71.4% efficent and my
Not bad for a Class D amp Thanks a bunch ------------- 2004 Honda Civic Ex 4Dr
Kenwood DDX-7015/W Nav
4 Fosgate T152C
Hifonics Brutus BX1500D
RE XXX 12 in a 4 Cube Snail Shell
Posted By: Francious70
Date Posted: February 25, 2005 at 11:17 PM
My amp is 500 RMS. The manual says use a 40A fuse.
14.4x40 = 576 watts input
500/576 = .87x100 = 87% efficent??? In a class A/B amp?? Huh??
Paul
Posted By: haemphyst
Date Posted: February 26, 2005 at 12:39 AM
As I said, this is a GRAND OVERSIMPLIFICATION. This formula takes the power supply AND the outputs into consideration. If you have a very efficient power supply (and most switchers are) and a not so efficient output, they will average in this formula. If you get a number TOO much above around 60 to 66% for a class AB, then I would suspect your manufacturer may be stretching the truth a little bit as for the output power... that or they offer a better protection system by underrating the input fuse. I expect your amp COULD take probably around 50A without damage (DON'T DO IT! THIS IS SPECULATIVE) and the mfr just wanted to extra protect it with a smaller fuse than is necessary...
Insofar as the digital amp, that sounds pretty close to the mark. In THEORY, digital amps can run as high as 95% efficient, but in PRACTICE, 70 to 80% is more like it...
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
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