Finally, The Class D Holy Grail?

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6 hours ago, Shadders said:

 

If you examine a class A/B signal, it is vastly more cleaner than the class D signal. Also, class D is an approximation to the signal which is filtered/averaged using a filter.

 

The real issue is that your hearing is not as good as you believe it is. You either have to agree that you cannot hear above 20kHz, and any information above 20kHz has no effect on what you hear, or if you agree that 20kHz+ signals make a difference, then why can you not hear the effect of the "mush" on class D amplifiers ?

 

Any amplifier output is a scaled approximation of the input.  If it is the modulation in Class D that bothers you, I wonder if you feel the same about sigma delta converters, DSD, etc.

 

I think I share your general point of view, though.  If the best Class AB amplifiers (e.g. AHB2) can provide comparable or better performance than the best Class D amplifiers, then I'd rather not have the switching noise even if it is not causing a problem.  Especially if the Class AB amplifier provides this excellent performance while also including Class H efficiency.

 

Rather than chase after lower and lower THD+N, I would rather see Class D advancements where the switching noise is made significantly lower.

 

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15 minutes ago, ddetaey said:

Any real life examples?

 

Dirk

Sorry, I don't follow you.  Examples of what?

[psjug]

1 minute ago, Shadders said:

Hi,

The class A/B amplifier is a continuous function, and the output is exactly the same as the input with added noise, whether harmonically related or not. It is not an approximation.

 

A class D amplifier is discrete time and discontinuous before the output filter. It can only be an approximation of the original signal.

 

Regards,

Shadders.

If the amplifier has any noise or distortion then I would say its output is an approximation, whether modulation is used to get there or not.  So a good Class D amplifier provides a better approximation than a bad Class AB amplifier.

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2 minutes ago, ddetaey said:

Examples of Class AB amplifiers with Class H efficiency.

Oh, I should have been more clear.  I was referring to the the Benchmark AHB2 that I mentioned.