amp efficiency

[cqtama]

this ^ boon wins

[corrie32]

actually i think it could go both ways, I'm looking in one of my old Car Audio mags. v6 of 2006, where they tested a Alpine PDX 4.150 and this is what they came up with

Efficiency at 1/3 power, 1%THD lowest impedence.............................72%

Efficiency at full power, 1%THD, lowest impedence.............................92

if anybody has an old Car audio mag, it's Volume 6, of 2006 , on page 37

and in volume 9 of 2006 the tested 2 full range class D amps

the Eclipse XA2000

efficiency at 1/3 power, lowest impedence...................................91

efficiency at full power, 1%THD lowest impedence........................89

Pioneer PRS-D2000T

efficiency at 1/3 power,lowest impedence..................................84

effeicieny at fulll power, 1%THD lowest impedence......................84

in all tests 2 ohm was the lowest impedence

so i could go both ways

Edited January 3, 2010 by corrie32

[JBurt09]

Amps are less efficient at lower ohm loads. They make more power but they take even more power to do so.

For example, completely made up but hey...

At 4 ohms, an amp might make 1000w and require 100A of input current to do it.

At 2 ohms it might make 1800w and require 200A to make it

Then at 1 ohm you might see 2400w but you will see close to 300A being pulled.

This, as mentioned above, is mostly due to inefficiency in the MOSFETs/Transistors and transformers used in the amp.

If you look at the specification RDS(on) for a MOSFET - this is the Resistance Drain - Source for a FET. It presents an in-line resistive load to the electricity in the amp.

Say we have 20A drain - source and the FET has an RDS of 5 milli-ohms.

The FET will drop 0.1v across it.

If we increase the current across the part to 60A we are losing 0.3v instead.

This effect is most pronounced in the power supply section where the parts are carrying heavy current at the supply voltage (12.x or whatever) so a loss of 0.3v equates to a loss of approximately 2% power.

This doesn't seem like much but it doesn't allow for the increase in temperature either. As the junction temperature rises the RDS increase as well, sometimes by a factor of 2 or even more. So suddenly you're losing 5% of your power just in heat going through the power supply section, and you see how it starts to add up.

This is quite possibly one of the best, most well explained and correct, educating comments on this entire site.Well said.

[Decaf]

This is quite possibly one of the best, most well explained and correct, educating comments on this entire site.Well said.

bah, he just explained more indepth what i said, lol

i try not to confuze da newbs

j/k boon, u know ur stuff bro... ive learned alot from you in the past

[REaudioBuff]

ok so i have 2 t2500.1bds running off of 2 kinetik 2400's. thats powering 2 12'' re mx subs... now do you think those batteries are a good enough bank? and i havent doen the big 3 yet should i do that even with my stock alt? its all in a scion tc only has a 100amp alt....

[Boon]

actually i think it could go both ways, I'm looking in one of my old Car Audio mags. v6 of 2006, where they tested a Alpine PDX 4.150 and this is what they came up with

Efficiency at 1/3 power, 1%THD lowest impedence.............................72%

Efficiency at full power, 1%THD, lowest impedence.............................92

if anybody has an old Car audio mag, it's Volume 6, of 2006 , on page 37

and in volume 9 of 2006 the tested 2 full range class D amps

the Eclipse XA2000

efficiency at 1/3 power, lowest impedence...................................91

efficiency at full power, 1%THD lowest impedence........................89

Pioneer PRS-D2000T

efficiency at 1/3 power,lowest impedence..................................84

effeicieny at fulll power, 1%THD lowest impedence......................84

in all tests 2 ohm was the lowest impedence

so i could go both ways

Full range Class D amps are completely ass-backwards when it comes to power and efficiency. The tiny little JVC ones make more power at 4 ohms than 2, go figure, haha.

[corrie32]

Full range Class D amps are completely ass-backwards when it comes to power and efficiency. The tiny little JVC ones make more power at 4 ohms than 2, go figure, haha.

True True!!