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Time to buy a class D amp?


Will some new class D amplifiers outperforming the current ones appear soon

(the newest ones i know were released a  few years ago)?

Class D amps attract me as I consider them the most ecological ones with obvious non-auditionable benefits.

I have no doubts that they posses the maximum ratio performance/sound quality among the amplifiers of all classes.

At the same time, the sound quality the class D amplifiers that I have auditioned produce, although is quite good,

but not yet ideal (for my taste).


I use PS Audio Stellar S300 amp with PS audio Gain Cell pre/DAC with Thiel CS 3.6 speakers in one of my systems.

The sound is ok (deep bass, clear soundstage) but not perfect (a bit bright and somehow dry, lacking warmness which might be more or less ok for rock but not for jazz music).

I wonder if there are softer sounding class D amps with the same or better details and resolution. Considering two reasonable (as to the budget) choices for test, Red Dragon S500 and Digital Audio Company's

Cherry  2 (or Maraschino monoblocks), did anybody compare these two?



128x128niodari
audiozenology
362 posts
 
atmasphere,
Would you say there is inherent limitation in the phase shift that is a factor of the comparator speed, digital logic delays, and turn-off time of the FET? What do you think a practical limit is on that? That may put a practical limit of a few-10 degrees at 20Khz, but that would be inaudible.
noble100's avatar
noble100
2,419 posts
 
Hello atmasphere,

     As I understand it from you and Bruno Putzeys as a layman, there is no such thing as too much feedback with class D amplification.  The generally accepted concept that feedback negatively effects the sound quality of traditional linear amplifiers may be true, but this aversion to feedback doesn't apply to class D amplifier design.  Very high levels of feedback, in an intelligently designed class D amp, are actually utilized to optimize the sound quality throughout the entire audible frequency spectrum.  
     Am I understanding this correctly?

Thanks,
  Tim
georgehifi's avatar
georgehifi
10,312 posts
 
Very high levels of feedback, in an intelligently designed class D amp, are actually utilized to optimize the sound quality throughout the entire audible frequency spectrum.
This can also be said about linear amps, but they sound crap when done. The goal is to have the best engineered design with the lowest distortions without negative feedback, and then if it can be done just a little local feedback around the input/driver stage to clean things up, but no global feedback compassing the output stage as well.

It was Matti Otala back in 1970-80’s that was the guy behind it all in solid state amps, and is still used today by the very best, but hard to design for. Look for today's amps that say in their description/specs "no global negative feedback"


Cheers George
audiozenology
362 posts
 
This can also be said about linear amps, but they sound crap when done. The goal is to have the best engineered design with the lowest distortions without negative feedback, and then if it can be done just a little local feedback around the input/driver stage to clean things up, but no global feedback compassing the output stage as well.



This is but one design methodology, and to say unequivocally it is the best is ... a leap not shared by all. It is more religion than science.

Can you define the time domain characteristics of feedback in a Class-D amp and linear amp?
georgehifi's avatar
georgehifi
10,312 posts
 


The proof will be in the pudding, as there are Class-D’s coming out with little or no feedback, Merrill Elements being just one with it’s said to be a very good sound.
From EE Online
"If none of these issues are addressed, it is difficult to achieve PSRR better than 10 dB, or total harmonic distortion (THD) better than 0.1 percent. The standard solution for compensate for the poor performance of a Class-D system is to add negative feedback, but a large amount of negative feedback increases Transient Intermodulation Distortion (TIMD)."
Question is does Putzey’s designs with large amounts of feedback, ever state TIMD "Transient Intermodulation Distortion" I think not only ever seen THD specified
https://pdfs.semanticscholar.org/b3c0/a892a982ebde91f83f228905dac30186f827.pdf

Cheers George
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