Are Class D Amplifiers really "digital"?

[kumakuma]

Recently one of our respected members expressed the opinion that Class D amplifiers couldn't be mentioned in this sub-forum because they are "digital".

 

Wikipedia seems to say that this isn't always true:

 

Quote

The term "class D" is sometimes misunderstood as meaning a "digital" amplifier. While some class-D amplifiers may indeed be controlled by digital circuits or include digital signal processing devices, the power stage deals with voltage and current as a function of non-quantized time. The smallest amount of noise, timing uncertainty, voltage ripple or any other non-ideality immediately results in an irreversible change of the output signal. The same errors in a digital system will only lead to incorrect results when they become so large that a signal representing a digit is distorted beyond recognition. Up to that point, non-idealities have no impact on the transmitted signal. Generally, digital signals are quantized in both amplitude and wavelength, while analog signals are quantized in one (e.g. PWM) or (usually) neither quantity.

 

What are your thoughts on this?

[kumakuma]

6 minutes ago, fas42 said:

 

 

 

Looks like Paul agrees with Wikipedia.

 

Quote

Many people believe that Class D amplifiers are actually digital when Paul argues just the opposite. Find out how a class D amplifiers work and what the differences between Class D and digital are.

 

[kumakuma]

@sandyk

 

You obviously feel Class D amplifiers are digital in nature. Why do you feel this way?

[kumakuma]

@sandyk

 

Please leave this thread or tell us why you feel the need to mark every post in this thread as off topic.

[kumakuma]

7 minutes ago, sandyk said:

Better still, you leave this Sub Forum as you are going against the main reason many members requested it. 

It was asked for as a digital free area where Vinyl etc. could be discussed without opposing views from the members who prefer pure analogue. 

 

This only makes sense if Class D amplifiers are indeed digital.

 

Did you watch the video created by Paul McGowan from PS Audio? He makes a pretty compelling case that Class D amplifiers aren't digital.

[kumakuma]

3 minutes ago, sandyk said:

Tom

Please stop trying to  turn this area into that which was not originally asked for by many members over the years.

 It is far too divisive , and may result in PMs sent that would almost certainly result in banning of their senders if reported .

 This has already happened in this Sub Forum

 

Alex

 

Please leave if you have nothing of value to share and, if you've got a problem with this thread, take it up directly with Chris.

[kumakuma]

3 minutes ago, sandyk said:

Discussions like this should be in the Objective area of the forum  .

 

Chris is free to move it there if he wishes.

 

[kumakuma]

11 minutes ago, Rexp said:

 

 

By his definition, a Class D amplifier is analog.

[kumakuma]

12 hours ago, Rexp said:

His definition of a digital signal is one with discrete values. 

 

It is my understanding that the pulse height has discrete values but not the pulse width but I could be wrong.

 

Found this interesting video:

 

 

 

https://www.psaudio.com/pauls-posts/dsd-and-class-d/

 

 

[kumakuma]

44 minutes ago, Rexp said:

Yes but the signal is off or on which is a definition of a digital signal. Analog signals are continuous. 

 

Yes, but unlike in digital systems, information isn't being conveyed by the on/off state of the signal but by the length of time that it stays on which isn't in discrete values or "digits".

[kumakuma]

10 hours ago, sandyk said:

From Silicon Chip magazine's Class D Amplifier.

 

Yes, the PWM waveform appears digital but the width of Vo will vary in an "analog" way. The non-digital nature of the waveform will be even more apparent when Vs is more complex than a sine wave.