Class A/AB vs D -- Is it Audible in 2021?

[red_kk]

This seems fairly achievable if most of the listening is done <10 watts.

What would <10 watts listening translate to in terms of dB ?

 

[watchnerd]

What would <10 watts listening translate to in terms of dB ?

Can't answer without knowing speaker sens and distance.

 

[Robin L]

I don't see unlimited SPLs with zero distortion speakers across the entire audio spectrum in our future any time soon.

Gawd, I hope not, it would rip a seam in the space-time continuum.

 

[JSmith]

Any amplifier topology can measure well and sound the way it is supposed to... it all comes down to design, implementation and parts cost.

Each has their own positives and negatives, all involve a tradeoff;

https://www.electronics-tutorials.ws/amplifier/amplifier-classes.html



JSmith

 

[red_kk]

Can't answer without knowing speaker sens and distance.

89dB sensitivity and 11ft away sitting position

 

[watchnerd]

89dB sensitivity and 11ft away sitting position

now you can plug that into here:

https://myhometheater.homestead.com/splcalculator.html

 

[red_kk]

now you can plug that into here:

https://myhometheater.homestead.com/splcalculator.html

For 10 Watts I get 91 dB SPL at my listening position. So are you saying that all my listening which is way below 90dB is using less than 10watts? I'm using Parasound A31 amp so am I a pure class A guy now?

 

[red_kk]

For 10 Watts I get 91 dB SPL at my listening position. So are you saying that all my listening which is way below 90dB is using less than 10watts? I'm using Parasound A31 amp so am I a pure class A guy now?

Something about this calculator doesn't seem right to me, if i'm using <10W of power why is the amplifier rated at 225W continuous output per channel? I'm never going to go over 80dB listening levels, i even measured with decibel app in iPhone which is pretty accurate give or take +/-3dB

At worst case listening of 80dB let us say there are peaks in the music worst case of +10dB that still gives me 90dB peak which is still <10W

I'm confused.

 

[daftcombo]

Something about this calculator doesn't seem right to me, if i'm using <10W of power why is the amplifier rated at 225W continuous output per channel? I'm never going to go over 80dB listening levels, i even measured with decibel app in iPhone which is pretty accurate give or take +/-3dB

At worst case listening of 80dB let us say there are peaks in the music worst case of +10dB that still gives me 90dB peak which is still <10W

I'm confused.

Peaks can be +20dB I think, if the music isn't very compressed.

 

[Geert]

At worst case listening of 80dB let us say there are peaks in the music worst case of +10dB that still gives me 90dB peak which is still <10W. I'm confused.

It's generally known that when listening at moderate levels in a modest home setting most people only need a few Watts most of the time. Exceptional speaker sensitivity or impedance or high music dynamic range can lead to exceptions that proof the rule.

 

[Alice of Old Vincennes]

As a diyer and sometimes customer, here is my opinion.

1. "Class D have better bass control" is a false statement in science point of view, but a somewhat valid one in commercial device.

Bass control is the combination of high damping factor and output current capacity of amplifier at the low load. Problem is speakers right now, especially bookshelf, have low sensitivity and low impedance with horrible phase in bass region. So the amplifier must be capable to deliver huge current at low impedance. Many amplifiers, especially tube amp or wimpsy amp, are not capable of doing that and reach a point of clipping at that moment. And with nature of clipping, the high THD effect caused by clipping will last a small period of time before it going back to normal. Class D amp, especially the good one, does not suffer from this effect. And that can be a different people heard.

In addition, class D like Hypex uses much more negative feedback than the normal class A/AB out there (Benchmark or Halcro or Soulution aside), so naturally class D amp will have lower distortion than the normal class A/AB on the market. Because of that reasons, the class D will have better bass control than the vast majority of class A/AB in the market. But if you have class A/AB amp with huge amount of current reserve and using good amount of negative feedback, their bass control to your speaker is the same

If class D exhibits inherently superior bass control over class AB, then why doesn't every consumer audio company simply switch to Class D? Pro audio companies have made great strides in recent years with Class D. Their customers demand light weight, reliability and reasonable fidelity. Amir hints at the difference in his reviews. His speaker reviews reveal the ohm problem. Speaker may average 4 ohms, yet dip down to less than 3. 6 ohm speaker may test at 4 ohm average. Why are most AVR companies still cramming A/B amps in their products? Panasonic tried the class D route. Why have competitors not followed suit? Some are using class D for lower demand surround channels. Are they waiting for the Hypex to come off patent? I really get a kick out of every explanation that class D is not digital. 0 is off and 1 is on. Sure sounds "digital" to me. The reserves provided by AB can be startling in the home environment. My son watched the goofy new Conguring movie on HBO Max. Those AB's crammed in the Anthem AVR made him jump. After Anthem room correction,. I have answered the door and and heard footsteps upstairs with 5.1.

 

[Doodski]

I really get a kick out of every explanation that class D is not digital. 0 is off and 1 is on. Sure sounds "digital" to me.

Class D amplifiers are very much a analogue amplifier. The musical waveform simply rides on top of the square wave and then the square wave is filtered out after amplification and the musical waveform remains. Very analogue. The square wave is not digital even though a square wave appears digital.

 

[JSmith]

Class D amplifiers are very much a analogue amplifier.

Pretty much... although some are more analogue than others;

To minimize IC cost, some vendors prefer to minimize or eliminate analog circuit content. Some products use a digital open-loop modulator, plus an analog-to-digital converter to sense power-supply variations—and adjust the modulator’s behavior to compensate, as proposed in Further Reading 3. This can improve PSR, but will not address any of the distortion problems. Other digital modulators attempt to precompensate for expected output stage timing errors, or correct for modulator nonidealities. This can at least partly address some distortion mechanisms, but not all. Applications that tolerate fairly relaxed sound-quality requirements can be handled by these kinds of open-loop Class D amplifiers, but some form of feedback seems necessary for best audio quality.

https://www.analog.com/en/analog-dialogue/articles/class-d-audio-amplifiers.html#

• All Amplifiers Are Analogue, but Some Are More Analogue Than Others

The definitive explanation why there's no such thing as a "digital amplifier", and why most
"digital" amplifiers are seriously fundamentally flawed.

https://www.hypex.nl/img/upload/doc/an_wp/WP_All_amps_are_analogue.pdf



JSmith

 

[carmol]

Class D amps have that LC network on output and high feedback,
this compromises their frequency linearity on complex speakers loads,
wich is very common.
At least those I tried, TPA 3255 and ta 2022.

 

[Matias]

Class D amps have that LC network on output and high feedback,
this compromises their frequency linearity on complex speakers loads,
wich is very common.
At least those I tried, TPA 3255 and ta 2022.

Try I high end ones like NCore or Purifi as these are more representative of what class D can do (state of the art).

 

[carmol]

Try I high end ones like NCore or Purifi as these are more representative of what class D can do (state of the art).

undoubtedly the high hend ones perform better,
but the combination of LC filter on the output, feedback and non-linear load is a critical point for this technology.
On resistive load they have a superlative response hovewer

 

[boXem]

undoubtedly the high hend ones perform better,
but the combination of LC filter on the output, feedback and non-linear load is a critical point for this technology.
On resistive load they have a superlative response hovewer

Ncore and Purifi amplifiers include the LC filter in the feedback loop and solve the issue of the non linear load.
Some reading:
https://www.hypex.nl/img/upload/doc/an_wp/WP_Globally_modulated_self-oscillating_amplifier.pdf
https://www.hypex.nl/img/upload/doc/an_wp/WP_Ncore_Technology.pdf

 

[carmol]

Ncore and Purifi amplifiers include the LC filter in the feedback loop and solve the issue of the non linear load.
Some reading:
https://www.hypex.nl/img/upload/doc/an_wp/WP_Globally_modulated_self-oscillating_amplifier.pdf
https://www.hypex.nl/img/upload/doc/an_wp/WP_Ncore_Technology.pdf

Texas Instruments implements Post Filter Feedback too,

https://www.ti.com/lit/an/slaa788a/...=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTPA3251

but in my measurements the issue is improved but not eliminated.
Cant say anything on ncore and purifi,
I believe that they perform much better,
but they are also quite expensive so the convenience comes
a little less, at that point it becomes just a matter of taste.
In the meantime, in doubt, I went back to a high-level AB class

 

[boXem]

Texas Instruments implements Post Filter Feedback too,

https://www.ti.com/lit/an/slaa788a/slaa788a.pdf?ts=1623089980798&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTPA3251

but in my measurements the issue is improved but not eliminated.
Cant say anything on ncore and purifi,
I believe that they perform much better,
but they are also quite expensive so the convenience comes
a little less, at that point it becomes just a matter of taste.
In the meantime, in doubt, I went back to a high-level AB class

If memory serves, Ti pffb represents 6 dB loop gain. Purifi 1ET400A has 80 dB loop gain at 20 kHz. You are comparing apples to oranges.
I seriously doubt that at equal performance a class AB amplifier is the same cost as a class D.

 

[DonH56]

Here's an overview of class D operation and why it is not "digital", not that I expect reality will cause anyone to change their mind...

https://www.audiosciencereview.com/forum/index.php?threads/class-d-amplifiers-101.7355/

Most if not all class D amplifiers today are self-oscillating but the basics are the same.