Class A vs AB vs D amplifiers

[rank]

So you're listening for the maximum possible distortion at very high volume levels?

Apogee was relocated in Australia and produced an easier to drive Definitive model rated at 4 ohms in 2014. But I didn't listen to it cos I have never met one at a hifi show. I heard the old Divas, they sound good but perhaps not better than the Magnepan MG III I owned.

 

[Koeitje]

So you're listening for the maximum possible distortion at very high volume levels?

Apogee was relocated in Australia and produced an easier to drive Definitive model rated at 4 ohms in 2014. But I didn't listen to it cos I have never met one at a hifi show. I heard the old Divas, they sound good but perhaps not better than the Magnepan MG III I owned.

You are missing the point I was trying to make. I was saying all amplifiers sound the same if they are operating within their design limits (i.e. not clipping).

 

[Blenderguy]

What I gather from this conversation is that the people who have speaker that have controlled impedance where even badly designed amplifiers will work properly there maybe no difference. I think the people that hear a difference will have speakers on the edge of impedance norm. And maybe on top will be inefficient. It is quite possible that driving an amplifier into clipping with those without one even aware this is happening. Not many amplifiers have clipping indicators on front panel.
So it mskes sense that others will never encounter these situations. I also suspect that many are also unaware of their hearing loss.

 

[Blenderguy]

But, but, but... everyone knows this stuff who has ever designed using BJTs and FETs. It was probably one of my first lectures of a 3 year EE degree course.

How do you prevent that from happening in an inductive or capacitive load? In an fully inductive load the current lags by 90 degrees. So when the top transistor is supposed to turn off, it still has to conduct the inductive current for another quarter cycle.

 

[Blenderguy]

I would call those speakers to badly designed. But its fun to talk about because of how silly those speakers really are

And why would you call them silly? I am sure you never heard them. Maybe you think champagne is silly, after all who wants to drink bubbly wine

 

[MaxwellsEq]

How do you prevent that from happening in an inductive or capacitive load? In an fully inductive load the current lags by 90 degrees. So when the top transistor is supposed to turn off, it still has to conduct the inductive current for another quarter cycle.

Google Boucherot cell or Zobel Network.

 

[Koeitje]

And why would you call them silly? I am sure you never heard them. Maybe you think champagne is silly, after all who wants to drink bubbly wine

I have actually heard them, some guy I bought a cd-player from had them. And they do sound good (not the best I ever heard, but not bad), but that doesn't make a speaker that drops to 1 Ohm well designed. A well designed speaker won't melt 99,999% of all amplifiers. That is just silly.

 

[Blumlein 88]

At 1 ohm I only know the old Apogees. The Full Range and even the Scintillas I think (the latter easier to drive). It's close to 0 ohm which seems problematic in theory but any real class A amp can hold them.

Like the Mark Levinson ML-2 or some Krells. For cheapos, the Hiraga in diy but I think he could no longer be repaired because of certain components having unfortunately disappeared without equivalence. The problem = the lack of power, old Apogees have low efficiency.

Knew someone with those Apogees. Class ab Classe amps powered them fine. I've owned ESLS that drop below an ohm. A good sized class D amp handled them better than any amp connected to them including some Classe amps.

 

[DonH56]

How do you prevent that from happening in an inductive or capacitive load? In an fully inductive load the current lags by 90 degrees. So when the top transistor is supposed to turn off, it still has to conduct the inductive current for another quarter cycle.

The output transistors in a class D amplifier (or SMPS, for that matter) are turned off by a switching network in the driver stage, that also guarantees both sides are not on at the same time. The passive output network supplies the charge after the output transistor is off.

 

[Holmz]

…
I would call those speakers to badly designed. But its fun to talk about because of how silly those speakers really are.

Hard to argue ^that^

At 1 ohm I only know the old Apogees. The Full Range and even the Scintillas I …

Scent’illas, when the smell of the amp escaping…

Might as well chuck on an L7 sound to test it out.

 

[rank]

I have no experience with D amps driving difficult loads or electrostatics.
Apart from the ESL 63 with a simple Quad 306 which never had the slightest problem.

As you are Australian, could you tell us about the current Apogee?

 

[JeremyFife]

Thought this was interesting, although light on detail.
TLDR: interview with Bruno Putzeys in PMA magazine stating that Class A design has stagnated, that Class D keeps improving and that amplifiers are not the weak link in the audio chain (speakers are). Interesting comment that Class A design could be improved, but no-one is bothering.

Is Class-A Amplifier Design Stagnating?

Robert Schryer dives into Bruno Putzeys' claim that class-A amps have stagnated, with only Nelson Pass responding to defend class-A in this heated debate.

pmamagazine.org

 

[MaxwellsEq]

Thought this was interesting, although light on detail.
TLDR: interview with Bruno Putzeys in PMA magazine stating that Class A design has stagnated, that Class D keeps improving and that amplifiers are not the weak link in the audio chain (speakers are). Interesting comment that Class A design could be improved, but no-one is bothering.

Is Class-A Amplifier Design Stagnating?

Robert Schryer dives into Bruno Putzeys' claim that class-A amps have stagnated, with only Nelson Pass responding to defend class-A in this heated debate.

pmamagazine.org

It's a thought provoking discussion. Given that there are only a limited number of ways to construct an A Class current delivery stage, perhaps there are no new avenues of research...

 

[Sokel]

Interesting comment that Class A design could be improved, but no-one is bothering.

What kind of improvement is he talking about though?
Spec-wise there are really good performing class A ones so he must be talking about efficiency,ways to get more power out of it without going enormous in size,etc.

 

[somebodyelse]

What kind of improvement is he talking about though?
Spec-wise there are really good performing class A ones so he must be talking about efficiency,ways to get more power out of it without going enormous in size,etc.

I would think any area of performance. Current Class A manufacturers seem to target the part of the market that doesn't believe measured performance is important, so there's no incentive to improve measured performance. Low/zero feedback may be seen as a selling point, not a shortcoming. High cost and large size are a positive in that part of the market, so there's little incentive to make them more efficient. Has anyone done anything on that front since the Aleph current source?

 

[mppix]

NO. Since as I said there is no perfect amp available. Each class has its benefits but also drawbacks. But one idea, why there are at least to my knowledge no preamplifiers in Class-D technology if this type is called better than A or AB.

The signal version of a class-D amplifier is a DAC. I believe we use them all the time.

 

[mppix]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

Huh? There are several class-D amps that compete in the relevant spectrum (even the NC400).

As for outside the spectrum, I would be curious what happens to speakers when fed a reference level sine-wave @ 0.1Hz or 200kHz

 

[rageworm]

I wanted to upgrade from my Emotiva BasX A2 to something like Yamaha A-s1200 eventually... I actually wanted that Yamaha for a couple of years now, but it seems like getting something like Buckeye 2ch ncx500 would be a much better choice. Sure, Yamaha looks nice, has knobs and solid phono stage, but speaking of amp performance, it seems like it isn't as good as ncorex/purifi. Not to mention huge difference in price.

 

[Papel65]

Ho misurato un sacco di amplificatori di classe AB e ho ingrandito la forma d'onda con una doppia base temporale in modo da poter vedere davvero se c'era anche un accenno di distorsione di crossover e tutti erano puliti e senza distorsione di commutazione a qualsiasi impostazione del volume. Ho posseduto un vero amplificatore di potenza di classe A made in USA che era lineare fino a 2 Ohm. Era un bell'amplificatore, era bello dentro e fuori e mi è piaciuto molto. Era colorato. Suonava come un amplificatore a valvole dal suono morbido. Non perché è di classe A ma perché il progettista apparentemente ha introdotto la colorazione nel risultato finale. Se fosse stato un puro classe A senza colorazione non avrebbe suonato diversamente.

salve, scusate ma di come suonano questi apparecchi non se ne parla?


Translated by mod

Hi, sorry but is there any talk of how these devices sound?

 

[Jimbob54]

salve, scusate ma di come suonano questi apparecchi non se ne parla?


Translated by mod

Hi, sorry but is there any talk of how these devices sound?

Please post in English . Thanks