Why can't a Sine Wave be used for testing high-power Class D amps?

[bibio]

Hi, amplifers like the lab gruppen PLM's:
https://www.labgruppen.com/product.html?modelCode=P0F66
Or the Crown I-tech range:
https://www.crownaudio.com/en/product_families/i-tech-hd-series

Try sticking a sine wave into an amp like this, it's not happy. I'm just trying to understand the technical reason why.

 

[Deleted member 21219]

It really just depends on how the limiting thresholds are set, which varies from manufacturer to manufacturer. They don’t want Gene killing an amp any more than an idiot who thinks he’s clever (the most dangerous type).

On my subs, I have access to all that, but I never dared mess with Funk’s settings.

Using the words "idiot", "moron", "shit", "dumbassery" and then claiming that it's simply honesty are not conducive to productive conversations. They are also not necessary; they are crude and abusive and indicative of argumentative and provocative individuals.

We don't subscribe to Emily Post at ASR, but we appreciate posters who use common sense and display respect.

Thank you.

Jim Taylor

 

[Steve81]

Using the words "idiot", "moron", "shit", "dumbassery" and then claiming that it's simply honesty are not conducive to productive conversations. They are also not necessary; they are crude and abusive and indicative of argumentative and provocative individuals.

We don't subscribe to Emily Post at ASR, but we appreciate posters who use common sense and display respect.

Thank you.

Jim Taylor

I’m not calling anyone here such names. I’m saying people who have no idea what they’re doing, and decide to push full power sine waves are idiots engaged in dumbassery…because they are.

 

[fpitas]

Hi, amplifers like the lab gruppen PLM's:
https://www.labgruppen.com/product.html?modelCode=P0F66
Or the Crown I-tech range:
https://www.crownaudio.com/en/product_families/i-tech-hd-series

Try sticking a sine wave into an amp like this, it's not happy. I'm just trying to understand the technical reason why.

What happens with a sine wave input?

 

[bibio]

The sinewave is reproduced by the amp but as the level is increased the amplifier heavily limits the signal. You don't get anywhere near the potential full output of the amp.

 

[fpitas]

The sinewave is reproduced by the amp but as the level is increased the amplifier heavily limits the signal. You don't get anywhere near the potential full output of the amp.

So you don't get the rated output?

 

[bibio]

absolutely nowhere near the rated output. I've been told before not to use sine waves for testing these amps, I'd like to understand why.

 

[fpitas]

absolutely nowhere near the rated output. I've been told before not to use sine waves for testing these amps, I'd like to understand why.

If they don't give rated output with a sine wave, that does sound like a major problem.

 

[bibio]

but this is how you evaluate a traditional Class A/B amp, using sine waves.

 

[fpitas]

but this is how you evaluate a traditional Class A/B amp, using sine waves.

Yes, or any amp.

 

[bibio]

I just found this online:
https://www.diyaudio.com/community/threads/test-signal-for-max-power-test-of-class-d.218513/

 

[SIY]

I've tested at least two dozen different Class D amps and have never seen any issue like this at all. Either you're grossly misunderstanding someone or you're reading stuff written by incompetents.

 

[fpitas]

I just found this online:
https://www.diyaudio.com/community/threads/test-signal-for-max-power-test-of-class-d.218513/

That just makes my brain hurt. Amir tests amps with sine waves all the time.

 

[fpitas]

reading stuff written by incompetents.

I was too tactful to say that, but...

 

[SIY]

I was too tactful to say that, but...

I'm not tactful.

 

[bibio]

FYI, I've only seen this issue on very high-power amplifier designs, small class d amps are totally fine.

 

[fpitas]

I'm not tactful.

One reason I fled that place years ago.

 

[SIY]

FYI, I've only seen this issue on very high-power amplifier designs, small class d amps are totally fine.

Please describe exactly what you've "seen this issue on very high-power amplifier designs," because that's arrant nonsense.

 

[fpitas]

FYI, I've only seen this issue on very high-power amplifier designs, small class d amps are totally fine.

Not sure how much power we're talking; but it should work fine nonetheless.

 

[SIY]

One reason I fled that place years ago.

That's an old post, from the time I was an admin/head moderator at that forum. Our policy was to not censor posts that were technically stupid, but rather to allow smarter members to correct things in public.