What are the reasons to choose Class A/AB/H over D in this day and age?

[Lambda]

The arguments about "phase shift" and "load tolerance" are utter nonsense.

Not utter.
If you load a class d output filter with a real reactive speaker impedance its something completely different compared to a test with a 4-8 ohm impedance.

There is gonna be some Phase shift and some distortion from the filter.
the question is how audible is it.

For a HiFi system i would go with Class D for the Sub, Low and Mids. but i would not bother with ab extra Class D for the Tweeters.
You need so little Power for tweeters its not worth the trouble and cost to uses an extra Class D for them.

 

[ebslo]

Short answer is amplitude phase shift and load tolerance.

This is not supported by the data. For example, see the Soundstage measurements ot the NAD C298. Specifically sections "RMS level vs. frequency vs. load impedance (1W, left channel only)" and "Phase response".

 

[Lambda]

This is not supported by the data. For example, see the Soundstage measurements ot the NAD C298. Specifically sections "RMS level vs. frequency vs. load impedance (1W, left channel only)" and "Phase response".

This. data shows a high end Class D performing Well with a purly Restive load.
Now do this test with you average cheap class d an an real reactive speaker impedance.

 

[DanielT]

There seems to be ambiguity about what is actually measured (what is captured) in terms of class D in any case, see from and post 1221:

Calleberg has some doubts, apparently. You can see this in the following posts in that thread. I suspect that it results in that if measurements had been made with bandwidth up to 80 kHz, the result would have looked different. Those of you who know more about measurements and how they should be performed in a sensible way can get involved in that thread. It was mostly a tip from me.

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[NiagaraPete]

Repairably speaking, I predict Class D amps will end up in a landfill more often than Class AB. So, pick your environmental poison - waste in electricity usage or waste in "waste".

I've been thinking the same thing. 40 year old AB amps are still running and can be serviced.

 

[ebslo]

I've been thinking the same thing. 40 year old AB amps are still running and can be serviced.

Classic survivorship bias.

 

[dguillor]

If this is not true then Class D manufacturers should give more than the typical 2 year warranty to help us believe otherwise.

I believe that most class AB amps don't have more than two year warranty. NAD amps have a two year warranty regardless of whether they're class AB or class D.

 

[ebslo]

This. data shows a high end Class D performing Well with a purly Restive load.
Now do this test with you average cheap class d an an real reactive speaker impedance.

Measurement of the same amp from Stereophile in Fig.1 shows frequency response into a "simulated loudspeaker load". Regarding "average" and "cheap" amps, this site is littered with measurements of poorly performing amps of all topologies.

 

[MakeMineVinyl]

Traditional class A and A/B amplifiers tend to be more interesting as objects in their own right, and thus lend themselves to audio as a hobby. This is doubly true of vacuum tube amplifiers. Class A and A/B amplifiers are relatively (or literally) massive and you can clearly see the technology in action. The sheer presence of these amplifiers is the point; pride of ownership is part and parcel for these amplifiers. They are the logical complement to beautifully finished and imposing loudspeakers.

Class D amplifiers are more like appliances, and its difficult for me to view them as an object of fascination. They are more for the person who wants efficiency in a box which does its job to near technical perfection and otherwise gets out of the way. They are for people who are more interested in the end product - the music or movie sound - and less interested in the bits which are making it possible.

Myself, I'm firmly in the class A / A/B camp, and almost exclusively vacuum tube. I can sit and be fascinated by the glowing tubes while enjoying the music they are enabling. A class D amplifier holds about as much fascination for me as my toaster or lawn sprinkler controller.

 

[sergeauckland]

I guess we're missing the point, if you have a perfectly good class ab amp why replace it with something only a tiny bit better, but newer and likely unrepairable at its core. I can fix my neurochrome amps, I can't fix the amp board on a class d amp, just the ancillary circuits.

I can't hear the difference, so why consume the resource.

That's pretty much my view on the issue. I currently use 3 Behringer A500s in my active main system, an old Technics SU-600 in my study, and Genelec 1029As for surround. Changing, for example, to A800s for my main system means throwing away some perfectly good Class AB amps for better Class D amps, but with what environmental impact? Ditto with my diesel car and Plasma TV. At what point does it become more beneficial to scrap the old technology for something more modern, than to carry on with the old? I don't know, so in the absence of any definitive ruling, I'll stick with what I've got, and only replace them when needed.

S.

 

[Ken1951]

It will be a tough decision for me when/if I have to replace my Adcom GA555. So used to the size/weight/look of the type of amplifier I've known for my entire awareness of Hi-Fi

 

[Lambda]

I believe that most class AB amps don't have more than two year warranty. NAD amps have a two year warranty regardless of whether they're class AB or class D.

In Germany every Consumer product needs to have at least two year warranty.

in Fig.1 shows frequency response into a "simulated loudspeaker load". Regarding "average" and "cheap" amps, this site is littered with measurements of poorly performing amps of all topologies.

I was talking about phase and it is Easy and cheap to make Class AB with Linear phase but it is harder to make this for an Class D

but newer and likely unrepairable at its core. I can fix my neurochrome amps, I can't fix the amp board on a class d amp, just the ancillary circuits.

Maybe you can't but some can
People Fix Smartphones and Laptops why not a Class D AMP?
Repeatability with modern products containing firmware is a real issue but Class D amp is relative easy and primitive compared to a Phone

I've been thinking the same thing. 40 year old AB amps are still running and can be serviced.

And on this am has used how mush energy in 40year compared to a modern Class D?
What is it remaining Objective value?

At what point does it become more beneficial to scrap the old technology for something more modern, than to carry one with the old?

If the New devices Saves more energy in its lifetime to pay for itself you can be sure.
Since the Price must contains Labor, Taxes, material and Energy cost to manufacture.

 

[SIY]

Not utter.
If you load a class d output filter with a real reactive speaker impedance its something completely different compared to a test with a 4-8 ohm impedance.

Yes, utter. These have everything to do with design (whether D, AB, A, whatever) and nothing to do with class.

 

[Frgirard]

Traditional class A and A/B amplifiers tend to be more interesting as objects in their own right, and thus lend themselves to audio as a hobby. This is doubly true of vacuum tube amplifiers. Class A and A/B amplifiers are relatively (or literally) massive and you can clearly see the technology in action. The sheer presence of these amplifiers is the point; pride of ownership is part and parcel for these amplifiers. They are the logical complement to beautifully finished and imposing loudspeakers.

Class D amplifiers are more like appliances, and its difficult for me to view them as an object of fascination. They are more for the person who wants efficiency in a box which does its job to near technical perfection and otherwise gets out of the way. They are for people who are more interested in the end product - the music or movie sound - and less interested in the bits which are making it possible.

Myself, I'm firmly in the class A / A/B camp, and almost exclusively vacuum tube. I can sit and be fascinated by the glowing tubes while enjoying the music they are enabling. A class D amplifier holds about as much fascination for me as my toaster or lawn sprinkler controller.

The power amp in my monitors kh420 and k+h o300 are little, little. 12 amps in AB class.

 

[Lambda]

and nothing to do with class.

Ok, shuld be easy to design an output LC filter that performs the same way independent from the load...

LCFILTER-CALC-TOOL Design tool | TI.com

View the TI LCFILTER-CALC-TOOL Design tool downloads, description, features and supporting documentation and start designing.

www.ti.com

 

[anphex]

I've got to admit, the size, power ratings and effort considering parts and design of some huge +50 Kg amps leave even me as a realist in awe. It's kind of like looking at a Bugatti Chiron and just appreciating everything like a piece of art. A piece of art I would never get for myself though because I am firstly following pragamatism, realism and the holy grail of price value. Considering this I can't help but fall back to Class D in recent times.
The points I got so far in regard of technical advantages: Class A/AB may have a longer life span and is easier to repair. Okay, that's a very valid point. Though there is the matter of objective and subjective obsolesce. Would a SINAD of 60-70 compared to newer available amps with +100 SINAD make your current obsolete...? Though question I can't answer myself since I went straight into Class D because I had the option available when I got into Hifi.

 

[usersky]

OP answer: I for one am not at all comfortabile with all that ultrasonic garbage entering my speakers so AB it is here.

 

[nc42acc]

OP answer: I for one am not at all comfortabile with all that ultrasonic garbage entering my speakers so AB it is here.

Doesn’t the use of the new GaN FETs help push the switching speeds much higher away from the audio band? Maybe less schmear? Maybe Bruno and Purifi will come out with a GaN amp soon.

 

[sq225917]

They make millions of iphones, they fail so there's a commercial market for fixing them. Class d amps are made by the thousands, tens of thousands if lucky, and the manufacturers don't offer repairs. The small brands might, those with a handful of staff, but the mainstream audio brands using off the shelf boards forget it.

I know one guy in the UK who could repair class d amps, and at his hourly rate you're better off replacing. I can service any class ab amp myself.

 

[ebslo]

Ok, shuld be easy to design an output LC filter that performs the same way independent from the load...

LCFILTER-CALC-TOOL Design tool | TI.com

View the TI LCFILTER-CALC-TOOL Design tool downloads, description, features and supporting documentation and start designing.

www.ti.com

Yeah, that's for the TI TPA3251. We can see from the "typical application" circuit diagram on page 21 of the datasheet that there is no feedback path from after the filter. The higher quality class-D amps mitigate interaction between the output filter and load by taking feedback from after the output filter.