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?

[fas42]

 

 

[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.

[sandyk]

 #30

[sandyk]

6 minutes ago, kumakuma said:

@sandyk

 

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

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. 

[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.

[sandyk]

35 minutes ago, kumakuma said:

 

This only makes sense if you can prove that Class D amplifiers are indeed digital.

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 the banning of their senders if they were reported .

 This has already happened in this Sub Forum, but you may already be aware of this ?

 

Alex

[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.

[sandyk]

8 minutes ago, kumakuma said:

 

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.

Discussions like this are best held in the Objective area of the forum  .

[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.

 

[Rexp]

 

[kumakuma]

11 minutes ago, Rexp said:

 

 

By his definition, a Class D amplifier is analog.

[Rexp]

13 minutes ago, kumakuma said:

 

By his definition, a Class D amplifier is analog.

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

[SoundAndMotion]

An intelligent, cogent argument can be made that Class D is analog.

 

An intelligent, cogent argument can be made that Class D is digital.

 

Professionally, we call this "a gray area". I assume the goal of this thread is for anyone interested to argue that this shade of gray is most definitely [black, white, both, neither]. Put me in the minuscule group who would argue "neither". I don't want to be the first to argue my point though, and I haven't looked for an authority (wiki, Paul, random youtube dude) to appeal to.

 

IMHO, discussion of what makes something "analog" or not could be intellectually stimulating and informative, and fits just fine in this sub-forum. Thread-crapping with armchair moderation seems OT to me. But I don't own the forum, nor am I a moderator.

 

I shouldn't need to point out that there are a couple of "Ignore" functions, so those who've set their hair on fire worrying that this topic is in the wrong place can protect their delicate eyes from the Medusan threat.

[R1200CL]

I liked the “secret” in the in Paul’s video.

Now that even Chris has become a class D owner, I look forward to what I has to say how that little amp he got performs upstairs.

 

In Bruno Putzeys interview you can learn something about his design. He also reveal what class A amp that may be equal to class D in about 6:45. And I must say one is not a very expensive amplifier. The other is totally crazy price.

 

[barrows]

No they are not.  Class D amplifiers modulate a switching output stage with an analog signal, and output an analog signal.  

 

But it also appears that there is an assumption inherent in the question that there is something wrong with digital audio?  Really? Anyone who currently thinks an analog recording played back by an analog system is superior to a digital recording played back by a competent digital system is mistaken (given care in the recording and playback chains).

[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/

 

 

[barrows]

2 hours ago, R1200CL said:

I liked the “secret” in the in Paul’s video.

Now that even Chris has become a class D owner, I look forward to what I has to say how that little amp he got performs upstairs.

 

In Bruno Putzeys interview you can learn something about his design. He also reveal what class A amp that may be equal to class D in about 6:45. And I must say one is not a very expensive amplifier. The other is totally crazy price.

 

Thanks for posting this interview, i had not seen this one before.  Beware folks, anytime you listen to Bruno Putzeys you might actually learn something valuable about audio circuit design, and audio performance, and what you learn, just might, be in direct opposition to your own strongly held beliefs (AKA myths)!

[R1200CL]

Some more inspiration. 
 

 

 

 

 

[fas42]

9 hours ago, R1200CL said:

 

In Bruno Putzeys interview you can learn something about his design. He also reveal what class A amp that may be equal to class D in about 6:45. And I must say one is not a very expensive amplifier. The other is totally crazy price.

 

 

Hmmm ...

 

Two measurements of distortion performance, at 1kHz into 8 ohms:

 

 

 

  

Which amplifier should give you the better performance, looking at those two AP graphs, at normal, rather than extreme listening levels? 😉

 

Surprise, surprise ... the first is of that extreme cost amp mentioned by Putzeys; the second is of a DIY construction project of a 20W class A unit using normal topology, published in a hobbyist magazine in 2007 ... 😁.

 

 

 

[sandyk]

2 hours ago, fas42 said:

Which amplifier should give you the better performance, looking at those two AP graphs, at normal, rather than extreme listening levels? 😉

 

Surprise, surprise ... the first is of that extreme cost amp mentioned by Putzeys; the second is of a DIY construction project of a 20W class A unit using normal topology, published in a hobbyist magazine in 2007 ... 😁.

 And that was using components that weren't selected for matching., where even better results were achievable.

 A little more work in the PSU area, as well as close matching of the differential input pair further improved it audibly 

Their ULD series of Class AB amplifiers would easily outperform that one too.

[Rexp]

13 hours ago, kumakuma said:

 

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/

 

 

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

[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".