The Sound and Testing of Class D

[Kenshin]

Originally posted by classd4sure
Sweep the frequency, step the power, multi tone tests.. can you think of others?
Regards,
Chris

Standard TIM test: 3.18KHz triangle & 15KHz sine, 4:1 mixed and fed into the input. If there's TIM, 900Hz signal would be generated at the output.

[IVX]

Kenshin,
nice link, however my Chinese limited by two words only -"Nihao" and "Combay". Well, i'll have to learn.

[soongsc]

Originally posted by IVX
Kenshin,
nice link, however my Chinese limited by two words only -"Nihao" and "Combay". Well, i'll have to learn.

You'll figure it out after a few "Combays" Good spice analysis though.

[Jocko Homo]

Well, we have to realize he's writing that paper to push his product. It's an advertisement.

No! Someone shilling their cr@p in an industry rag? I'm shocked.

"Round up the usual suspects."

Whatever he ws selling, didn't convince me. I'm not buying. (You will notice his reference to to jitter.............leads one to believe he is measuring Bose-grade amps.)

Jocko

[ghemink]

Originally posted by classd4sure


An analog computer, couple op amps.... yeah, nothing's faster

Are you guys seeing the possibilities like I am here?

It's more than just simplicity, it's the strong visual aspect of it, everyone knows what a straight line should look like, so that's all you need to compare it to.

I think a multitude of tests could be still be done while expecting to see the same straight line output.

Sweep the frequency, step the power, multi tone tests.. can you think of others?

I was impressed that Mueta gave a linearity graph on their recent update, but I think they swept frequency and kept the gain constant. Why leave it at that?

Regards,
Chris

I think an analog computer is not needed, you just need enough gain in front of your soundcard so that the dynamic range limitations of the soundcard are not the limiting factor. Using analog conputers may give you trouble with phase differences between input and output signals and with the HF carrier frequency of the UcD. We would have to filter out the HF carrier from the output signal as it could easily overload the DAC and gain stages before the DAC.

I expect the UcD to be pretty linear though as it does not digitize the input signal and does not use digital input signals. The noise level is also very low, indicative for a good dynamic range?

Best regards

Gertjan

[classd4sure]

Hi,

UcD keeps comming up in this thread lol. It's funny. It's got a death grip on the industry. Of course I would like to see some graphs of it like that, I'll let Jan-Peter do them.

Such a measurement should be good for any amp of any kind.

If we could do it ourselves in a meaningful way though it could be very interesting for tweakers and experimenters who dont' have AP2s etc.

You make some excellent points about the problem with an analogue computer. Any solution would take some thought. I do have a good sound card for taking measurements with so I'd be interested in making that work.

Regards,
Chris