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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?



niodari
audiozenology
362 posts
 
Servo controlled woofer is much different from a low output impedance amplifier connected to a woofer that will keep moving after the amplifier signal goes to 0. A servo controlled woofer can be designed to smoothly stop a woofer without any ringing if so desired.


"Damped" and damping factor are of course not the same thing. Damping factor is a simple output impedance  / 8 Ohm calc.  "Damped" refers to how or the characteristic of how a system will respond to a step response.


Speakers are designed to be driven typically by constant voltage sources. Dynamic drivers on the other hand can behave better, i.e. lower distortion with constant current sources.  To that end, all speakers are the product of trade-offs, and designing for 0 output impedance forces other trade offs a particular designer may not want to make. The amplifier is part of the circuit that governs how the speaker will behave. We can talk about a "perfect" world, but dynamic drivers are already imperfect. So better to discuss which imperfections you want to live with.
georgehifi's avatar
georgehifi
10,312 posts
 
Servo controlled woofer is much different from a low output impedance amplifier
I didn’t say it was the same, I said it controls even better the cone movement than the amps damping factor alone can.
I’ve asked you three times now, go away please, and stop stalking my posts.
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
12,180 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.
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