Some clarification....

[Frankensuby 10+ year member]

Just need to make sure I'm thinking right.

If an amp says that it's THD is .02% at 90 RMS, if I run the amp at 70 RMS, there is even less distortion? I know running it above it's ratings at sine wave increases distortion, but does less reduce it?

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[stratastic 10+ year member]

i could be wrong but i believe that .02% is the min distortion that the amp will produce at any given level

 

[luvinthebass 5,000+ posts]

tha'ts .02% at that 90 rms not at any given level...i think

 

[mike dressure 10+ year member]

not exactly sure but i think luvinthebass is right

 

[creyc 10+ year member]

Depends on how its rated. Manufacturers are SUPPOSED to rate the distortion at their rated power output, but some companies will rate distortion way below their rated output just to get a better number.

Unless you drive the amp harder than where that distortion measurement was taken, it won't distort worse that that, no.

 

[T3mpest 10+ year member]

The distortion rating of an amp, in my experience is fairly flat. Looking at my arc's birthsheet it shows the distortion actually dropping as power is increased, but it's minimal. It's goes from .05 to .02 over a 500 watt range. Really it doesn't matter, all the variations on the graph are inaudible. Anyway,, once it hits 500 watts it shoots almost straight up. The next 50 watts are where it hits it's maximum allowed thd, 1% Like I said though, you won't hear it.

 

[thylantyr 10+ year member]

Random thoughts;

* Don't rely 100% on amplifier published specs to form conclusions.

* Distortion numbers will change based on frequency tested.

I have the 'binks'proamp shootout at those amps are tested at 1% THD+N

with 20hz, 1khz, 20khz tests. Each amp will reach 1% distortion at different power levels

at those different tested frequencies. 1% THD is considered the upper range of

inaudibility, but some folks can't even hear as high as 3% THD.

What is interesting is many of those amps output less power at the lower

frequency when it hits 1% THD+N. So, the 20hz score is lower power than

the 1khz score and less power than the 20khz score. Some amps are weird, they

output much less power at 20khz than the other frequencies so their topology

is suffering at high frequency playback.

Here's a very high end amp;

rated: 2200w/ch @ 4 ohms 20hz - 20khz

Tested;

20hz power = 1327 watts

1khz power = 2310 watts

20khz power = 648 watts

This amp really fails at 20hz and 20khz, outputting much less power

than rated at 1% THD.

Here's another very high end amp;

rated: 3200w/ch @ 4 ohms 20hz - 20khz

Tested;

20hz power = 3152 watts

1khz power = 3293 watts

20khz power = 4804 watts

This amplifer is much closer to published spec and it exceeded spec at 20khz testing.

Bottom line, any amplifier is subject to this even if it's a car amp, home amp,

pro amp, what they do in real life can be much different than ratings.

The last variable is the input power you give the amp. Those number can be different if

the supply voltage sags below nominal.

I don't know how valid birthsheets are either, will a manufacturer *really*

show you a bad birthsheet? lol ...

 

[Team Hammer 10+ year member]

Random thoughts;
* Don't rely 100% on amplifier published specs to form conclusions.

* Distortion numbers will change based on frequency tested.

I have the 'binks'proamp shootout at those amps are tested at 1% THD+N

with 20hz, 1khz, 20khz tests. Each amp will reach 1% distortion at different power levels

at those different tested frequencies. 1% THD is considered the upper range of

inaudibility, but some folks can't even hear as high as 3% THD.

What is interesting is many of those amps output less power at the lower

frequency when it hits 1% THD+N. So, the 20hz score is lower power than

the 1khz score and less power than the 20khz score. Some amps are weird, they

output much less power at 20khz than the other frequencies so their topology

is suffering at high frequency playback.

Here's a very high end amp;

rated: 2200w/ch @ 4 ohms 20hz - 20khz

Tested;

20hz power = 1327 watts

1khz power = 2310 watts

20khz power = 648 watts

This amp really fails at 20hz and 20khz, outputting much less power

than rated at 1% THD.

Here's another very high end amp;

rated: 3200w/ch @ 4 ohms 20hz - 20khz

Tested;

20hz power = 3152 watts

1khz power = 3293 watts

20khz power = 4804 watts

This amplifer is much closer to published spec and it exceeded spec at 20khz testing.

Bottom line, any amplifier is subject to this even if it's a car amp, home amp,

pro amp, what they do in real life can be much different than ratings.

The last variable is the input power you give the amp. Those number can be different if

the supply voltage sags below nominal.

I don't know how valid birthsheets are either, will a manufacturer *really*

show you a bad birthsheet? lol ...

Thats some good Information, I Printed this out just to keep in my file.

These values change when you wire them in Series. I seen them jump all over the Scope when you add Two or more on a channel.

 

[Frankensuby 10+ year member]

Hmm, well that blows in a way haha. Thta means whatever amp i get, I'd have to run a similar test to see what is going on?

Atleast I know better now.

 

[thylantyr 10+ year member]

Send me a an email if you want a copy of the binks pro audio amplifier test.