Accuphase amplifier choice

Conclusion:
Accuphase’s Class A amps are genuinely Class A within their rated range — not just “high-bias AB.” Their engineering and thermal performance confirm that. However, they’re designed sensibly so that they can exceed that range without distortion by sliding into AB operation.

Would you like me to show you some measured bias current or power consumption data from bench tests (like Stereophile or Audio Accessory reviews) to illustrate this?

@westcoastaudiophile 

I currently own an Accuphase A-48S as I previously mentioned and I thoroughly enjoy it!  This is the best amp I've ever owned but I will upgrade to the Accuphase A80 sooner than later. How, when or even if the A48-S Class-A operates in Class AB is beyond me,  but I can definitely tell you that I can hear a sonic difference and this difference compelled me to purchase this A48-S.  It sounded great with the Fyne Vintage 15 and I'm enjoying it with my LaScala AL5 spkrs and that's all that really matters at the end of the day. 

@fire_water congrats with A48s! excellent amp., with 105dB @ 2.83V / 1m (WOW!) AL5s Scala you have symphonic orchestra playing live in your house with less than 50W p/ch for sure! 

..as of AB vs A class amp design definition it’s simple: class A amp has maximum theoretical efficiency of 25%, which means x2 ch 50W @8Ohm load amp will burn 400W in idle (no signal) state, while claimed 100W p/ch @4Ohm should dissipate 800W, which is not the case for Accuphase, per spec it is 200W idle, thus it’s actually designed as high bias AB class amp! I admire and enjoy Accuphase presence/amps performance tho! 

Accuphase class A amps are AB class amplifiers biased to the clipping point for 8+ Ohms load.. Accuphase class A amps are AB class amps if load is below 8 Ohms, e.g 6/4/2 Ohms. Thus there is not much difference between Accuphase AB and A class amps!

The above is more or less true of all push-pull Class A amps.

Only with single-ended designs can you be certain that the amp runs 100% in Class A 100% of the time.

@milpai Sometimes us audiophiles (including yours truly, of course) use terms like ’warm’ or ’neutral’ rather loosely. I would like to understand why you think Accuphase Class A is ’warmer’? More importantly, how are you interpreting this term?

The reason I ask is that many people sometimes conflate a slight roll off in the upper frequencies as ’warm’. Yet others think warm is the same as lack of details.

From my experience, having lived with Accuphase A-80- for almost 10 months now (i.e., I’m done with the honeymoon phase :)), there’s nothing warm about the amp. In fact, there’s a certain sparkle (not to be confused with bright or etched) in the treble region which can only be attributed to class A. The sound is liquid smooth, balanced, and natural without exaggerating any areas of the frequency response. Further, it has a very high damping factor and tons of reserves in the tank that deliver regardless of the wattage numbers. 

Having lived with class A, AB, and D amps, all I can tell you is that class A watts are more than what mere numbers suggest. Without exception, all my class A amps sound much more potent compared to the same wattage in class AB or D. I’m sure someone will slap me with "watts are watts" and "all watts are the same" argument, but I’m just sharing my personal experience.

At the end of the day, it is your system, your room, and your ears. Just because I favor class A doesn’t mean you will share my enthusiasm. You might still prefer AB after all. However, if there’s a possibility of auditioning the A48S in your system, I highly recommend it. Reviews and opinions only give you a partial picture. 

But either way, even if you go with Accuphase class AB, it is still an Accuphase and will make you very happy. Good luck and let us know what you end up with.