Effect of measuring bandwidth on class D amplifier measured THD and THD+N parameters

[SoNic]

He tests one version of IMD (I prefer the twin tones at 18+19 khz), he doesn't test for DIM don't know I've seen anyone who regularly does. He does do a multitone which would show IMD even if not at the specific frequencies in the DIM test. He tests for FR, distortion at different levels and other things. The point being not that his tests are totally comprehensive, but that they are far more than a one shot one SINAD number and call it done. Yet you posted, "People keep saying that THD+N is all you need to know, because one sinus signal is sufficient." Like SIY, who says this? I only see people claiming other people saying this not anyone who does say this.

I just looked a a few AMPLIFIERS and there is just normal THD shown.
I saw a lot of people here say that THD+N is all you need, I don't need to provide a list, I am not at an congressional hearing.

 

[SylphAudio]

The effect of the isolation transformer is indisputable.

Have you tried the setup without connecting the notebook/laptop to mains and run only with its battery? It should have a similar effect.
Also make sure that your dummy load is exactly 4 ohms. Using 4.2 ohm vs 3.7 ohm will have a widely different SINAD result, some amps will lose around 3dB just by using a slightly lower impedance load.

 

[fpitas]

I just looked a a few AMPLIFIERS and there is just normal THD shown.
I saw a lot of people here say that THD+N is all you need, I don't need to provide a list, I am not at an congressional hearing.

Wait...what? We just showed you 32-tone IMD testing. For an amplifier.

 

[SoNic]

Once you've climbed the "I am right and everyone else is wrong" pole it is very hard to get back down.

What are you talking about???
Where did I say THAT?
This is a toxic attitude, that anyone with different opinion than yours is automatically wrong.

 

[fpitas]

What are you talking about???
Where did I say THAT?
This is a toxic attitude, that anyone with different opinion than yours is automatically wrong.

Definitely. I am always right, and anyone who even thinks differently is deluded.

 

[SoNic]

Wait...what? We just showed you 32-tone IMD testing. For an amplifier.

I looked at others and doesn't have that.
Anyway, my OP didn't have ANYTHING to do with how Amir tests.
But how MANUFACTURERS are testing.
Adding a straw man into discussion just to contradict people is weird.

 

[fpitas]

I looked at others and doesn't have that.
Anyway, my OP didn't have ANYTHING to do with how Amir tests.
But how MANYFACTURERS ar testing.
Adding a straw man into discussion just to contradict people is weird.

It is hard to argue with reasoning like yours. So, I give up.

 

[Sokel]

Show me where does Amir test IMD or DIM for amplifiers.

And regardless, I was talking about manufacturers of class D amps not showing those numbers.

I don't think they don't,there's one of my amps:

Whole datasheet here:

300A2 - ICEpower

Featuring our proprietary ICEedge class D chipset, the 300A2 is a stereo amplifier module capable of 2 x 300W output capable of being bridged for 600 W and 70V constant voltage output. The 300A2 is designed to be used alone for a standard 2 channel amp or combined with multiple modules to serve...

icepoweraudio.com

 

[fpitas]

I don't think they don't,there's one of my amps:

View attachment 268775

Whole datasheet here:

300A2 - ICEpower

Featuring our proprietary ICEedge class D chipset, the 300A2 is a stereo amplifier module capable of 2 x 300W output capable of being bridged for 600 W and 70V constant voltage output. The 300A2 is designed to be used alone for a standard 2 channel amp or combined with multiple modules to serve...

icepoweraudio.com

Sure. Hypex, NCORE, Purifi do too. I think we're being, uhm...there's a word for it, but it escapes me at the moment.

 

[SIY]

But how MANUFACTURERS are testing.

So, I'll ask again- specifically, which manufacturer is doing strictly single tone tests and that's it? Name ONE. I'm reasonably familiar with the industry and I have never ever encountered this. I suspect you're making it up.

You were caught in an error, and that's OK, we all are from time to time, and being corrected is how we learn. Don't compound error by moving over to out-and-out lying, learning and correction is much superior.

 

[SoNic]

I don't think they don't,there's one of my amps:

View attachment 268775

Whole datasheet here:

300A2 - ICEpower

Featuring our proprietary ICEedge class D chipset, the 300A2 is a stereo amplifier module capable of 2 x 300W output capable of being bridged for 600 W and 70V constant voltage output. The 300A2 is designed to be used alone for a standard 2 channel amp or combined with multiple modules to serve...

icepoweraudio.com

That's not the DIM that I was talking about.

 

[SIY]

That's not the DIM that I was talking about.

Well, what ARE you talking about? You've made a lot of assertions which seem, ummm, odd, yet have not backed up a single one of them with specifics.

 

[Head_Unit]

IMD 18 + 19 kHz 10W

I find it really interesting how quite different each of these amplifiers measures. Not shocking, but mildly surprising, since none of them are cheap.

 

[Head_Unit]

The main reson of isolation transformer use is to eliminate capacitive leakage currents from SMPS.

Interesting-can you explain more? Why does the transformer reduce the junk? And how much does it cost?

 

[Julf]

Then remember that musical programs have an infinity of sine wavers (Fourier transformation).

No, they don't.

 

[dlaloum]

Because measuring what's audible will lead to conclusions that don't benefit advocacy of old-fashioned amplifiers.

There have been double blind tests that came to the conclusion that regardless of topology, as long as the amps are run within their performance envelopes (power, impedance of speakers driven, etc...) - all "quality" amplifiers sound the same. (and the definition of "quality" need not be an overly onerous high bar... decent basic amps as packaged into mass market AVR's qualify!)

The conclusion being - choose an amp that can provide the power you need, into your specific speakers... and then don't fuss too much about the amp!!

 

[Verig]

@pma I've always found class D measurements interesting. However, do you happen to have any material about audibility and perceived quality? Is the distortion noticed at all or differently than with A/B? Yes, distortion is distortion but a group average telling that class D is usually heard in certain way?

At work I'm taking a look at VoLTE MOS, how our automation picks up bad quality "line" and how the audibility is scored. Very interesting stuff but the errors and distortions in call traffic are in totally different class than some hedgehog at -110...

 

[Ricardus]

I think we have found another one of the new account trolls.