How does Class D work?

[travis]

I understand the basics of the circuit, but I don't understand how the pulses can sound like music, or like the source music anyways.

Links to articles?

[Electrone]

It works by integrating the short on-off switching of the power so that the human ear just responds to the varying audio inserted into the output signal.

[raintalk]

"How does Class D work?"

It works very well - thank you

A good explanation here:
http://en.wikipedia.org/wiki/Switching_amplifier

That Low pass output filter is a big discussion. Plenty of threads here.
With the filter the class-d does present to the speaker the same signal that would come out of any amp.

[travis]

Originally posted by raintalk

With the filter the class-d does present to the speaker the same signal that would come out of any amp.

You're blowin' my mind, raintalk.

[wwenze]

Originally posted by travis


You're blowin' my mind, raintalk.

That's in theory of course, and in theory all amps should sound sound the same.

But we're in reality here.

And that most class-D amps in the market are for cheapo applications (i.e. computer speakers) doesn't help.

[ssanmor]

Hello,
I wrote and published this some time ago. I would add some comments today, but I think it will help you understand the operation of Class-D and what the limitations were/are.

Hope it helps:

http://sound.westhost.com/articles/pwm.htm

[travis]

Originally posted by ssanmor
Hello,
I wrote and published this some time ago. I would add some comments today, but I think it will help you understand the operation of Class-D and what the limitations were/are.

Hope it helps:

http://sound.westhost.com/articles/pwm.htm

First thing I read. Great site.

I just didn't get how the filter turns the pulses back into the original signal. I was thinking running those rectangular pulses through a low pass would make rectangular pulses with rounded corners.

[Eva]

The pulses are generated in a way such that they already contain the audio signal, plus the high frequencies that are attenuated by the filter. That's the trick.

[Pafi]

I was thinking running those rectangular pulses through a low pass would make rectangular pulses with rounded corners.

Freq of the pulses (eg. 400 kHz) is much higher than cutoff freq of the filter (eg. 30 kHz), so at the output there is no switching freq left, just audio.

[Gyula]

Freq of the pulses (eg. 400 kHz) is much higher than cutoff freq of the filter (eg. 30 kHz), so at the output there is no switching freq left, just audio.

Maybe in an ideal world, it would be true.