Why Class B and not Class AB in Naim amps?

As I understand, Naim uses class B in its amplifiers.
Why is this, when class B gives more crossover distorsion than class AB?
Most amplifiers normally use classAB.
I could be wrong of course…

thought they were all class a/b?

They are class AB.


Self awareness, the necessary first step…….



Agree. I just wish I, wasn’t so self aware. I think I’d be a lot more confident. :nerd_face:

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Ok, I read in some review they are class B.
And, at least my SN3 barely gets lukewarm in idle. All my other AB amps get noticeably warmer.

Naim amplifiers have been class AB for 50 years :slight_smile:

FYI the class AB bias current is small, just enough to stop crossover distortion and not too much to cause the lesser known ‘gm-doubling’ distortion.

For each new amplifier we measure an acceptable range on the bench. Then try each setting until it sounds best.



Here’s a quickie (a very quickie!) on the different amplifier topologies. Bear in mind that a high quality, well designed class B amp cam sound better than a poor quality, poorly designed class A amp.

What are the differences between Class A, AB, and Class D amplifiers.


Ok, thanks Steve.
Good to know.

I have a friend running a pair of 105db Klipschorn’s with a NAP500. Because he’s only using 1/4 watt to fill the room its class-A all the time. I’m told the sound is remarkable.


What is the hiss like with such high sensitivity speakers (making it 15-20dB louder than the majority of hifi speakers)?

Good question. I don’t know.

Damn. And here I sit with my 87db speakers and a 300DR.

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True class A all the way is lovely, it’s certainly not the most efficient way to do it, and not sure how naim does it, but it certainly sounds better i agree.
True class A amp is running at max out put all the time, that’s why they get hot, and need a very big reserve off power due to running at max all the time for the big dynamic pieces in the music, as if not they suffer with being dynamic

I feel an FAQ topic on the way…


I’d certainly agree that Class A amps can sound “lovely”, but not so sure they always sound better than other classes. For many years I ran my system with a pair of Musical Fidelity Class A monoblocks. The sound was silky smooth with absolutely nothing to scare the horses. Audio nirvana for many, I guess, and for me initially. But gradually I found the system too easy going and listened less and less. The Class AB amps in the power packs of the active ATCs I now use are not as silky smooth as those old class A boxes, but I now get much greater connection with the music and listening pleasure.

As with so much hifi, there’s a temptation to believe that one technology is intrinsically and always better than some other, whereas, in reality, the way it is implemented and a host of other things make comparisons more complicated than that. My MFs would surely have had a very different sound from monster class A Krell amps!



Which model was that?

I guess i am very lucky then as i can push a button on the remote and go into class B.
I can also switch over to a rock mode, this has the tendency to alter the sound stage slightly and moves it forward more, i don’t use this as i much prefer the classic mode ( normal ) plus i leave it in true class A ( 30 w per channel max ) as this also sound’s better.



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When I graduated in electronic (and computer) engineering three decades ago push pull audio power amplifiers with low distortion were always class AB and not class B. That is the push pull driver stage configuration was biased with respect to the small signal to the more linear part of the driver transistors transfer curve so as to minimise distortion and cross over distortion at the cost of less efficiency. Class B amplifiers were for applications where harmonic distortion was irrelevant but efficiency and heat dissipation were more critical such as FM RF power amplifiers.
In fact I remember a module on exactly this topic where we, in groups, had to design and build a class AB amplifier from first principles and measure its performance.

Class B audio amplifiers by definition would always sound awful… (think guitar fuzz box).

I probably still have my lecturers book on the subject somewhere in the house.