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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
 
This is a public forum. I will respond to the content of your posts if I please. That is how public forums work. You didn't start this thread. Lose the attitude.

An amplifier with a high damping factor may limit the total error energy in the woofer cone movement, which could be one measurement of "better", but there is no guarantee that will sound better, because the energy may be concentrated over a narrow frequency range (ringing) that is audible, compared to what happens with an amplifier with a lower damping factor. This is not a new concept, and is explored in the item linked by Nelson Pass, and has been discussed on/off since the 70's.


This is much different from a servo controlled woofer movement where the actual physical position is directly controlled, not an indirect via the coil wires (and through the cross-over).
atmasphere's avatar
atmasphere
11,662 posts
 
In theory the "signal" stops and starts as recorded so that is accurate. The problem is the woofer does not stop right away. In a lower damping factor amp the output resistance will help dissipate the energy in the woofer which can give it a more controlled stop.
This is of course the theory but in practice (IOW the real world) is not a thing. The woofer never 'stops'; its always in motion; there is no recording where the woofer 'stops'. The only way for it to 'stop' as often described abover is if a DC pulse is being reproduced, which is something that neither the amp or speaker will ever have to do. On this account I've often viewed this as a red herring.


More to the point, the idea is that the woofer will continue to oscillate after the initial pulse. But in reality after the woofer moves the first way, the audio signal directs it in the opposite way; it never gets the signal removed and so can't ring. This is why amps with a low damping factor can do quite well in the bass. The real problem isn't ringing or distortion, but getting too much bass if the amp fails to reduce power into impedance peaks of the woofer's impedance curve. This isn't a control issue (which is also a problematic idea), its simply that an amp with insufficient low impedance will simply make too much power. 
audiozenology
362 posts
 
Can you read your full last paragraph? I think the wording in your last two sentences contradicts though I know what you mean. I agree this is an issue. I also agree that the audio signal never stops, but decays within bandwidth limits. However overly low impedance can accentuate ringing.  I get the impression you would be familiar with snubber circuits?  It is similar to a resistor in series with the capacitor. The resistance is needed to damp ringing.
atmasphere's avatar
atmasphere
11,662 posts
 
Can you read your full last paragraph?
Yes- in rereading it, it makes sense to me...

However overly low impedance can accentuate ringing. I get the impression you would be familiar with snubber circuits? It is similar to a resistor in series with the capacitor. The resistance is needed to damp ringing.
Usually those snubbers you see in amps are for the amp’s benefit, not that of the loudspeaker. But keep in mind almost any amplifier will provide damping to almost any loudspeaker. But the simple fact remains that there is no signal in audio where the ability to stop on a dime is important.


As I just pointed out, once the woofer nears the zero crossing point it will want to keep going for a bit, but once it gets to the zero crossing point whatever signal that allowed it to get there will also be calling on it to continue in the same direction past the zero crossing point. There never is a point where the woofer stops unless the amp is shut off.


So the two points of stopping are:
*a DC pulse, or
* the amp being turned off
In either event no audiophile listens to either so its moot :)

audiozenology
362 posts
 
I was thinking more of snubbers for diodes (transformers), but realistically any circuit with reactive elements.  The output impedance of the amplifier is part of the overall electrical circuit and hence the total electro-mechanical assembly and hence impacts ringing/resonance. I guess I made my point poorly ;-)
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