Pass Labs Xa60.8 Class A or should it be called class A/B?

Contact Desmond at Pass. He is extremely helpful. 

I’m assuming that all the output above 122 watts (at least for 8 Ohms) is class B. Makes sense and shows tons of headroom. I can’t wait to get a set of these.

From JA/Stereophile, 
"Specified as putting out 60W into 8 ohms and 120W into 4 ohms (both 17.8dBW), the XA60.8 considerably exceeded that power, delivering, at 1% total harmonic distortion (THD), 150W into 8 ohms (21.8dBW, fig.4), 240W into 4 ohms (20.8dBW, fig.5), and 380W into 2 ohms (19.8dBW, fig.6). The THD begins to rise above the noise floor at high powers, but remains at or below 0.1% below the specified output power. The percentage of THD then slowly rises with increasing power, suggesting that the XA60.8 has only a small amount of corrective feedback."
Charles 

Could possibly/ likely be 60 watts of class A into 8 ohms and 120 watts class A into a 4 ohm load.
Charles 

I'm puzzled as well, since peak power of 60W sinewave is 120W.  Most of power comes from low frequencies and it is likely to be close to sinewave.  Does it mean that headroom of this amp is only 2W?

Let's think about it the other way round.

How many amps described as class A/B offer 122w of class A power?

All ‘class A’ power amps transition to A/B at high levels!

Sorry not true.  The distinguishing characteristic of a true class A amplifier is the quiescent current is at maximum with 0V output and to produce output away from zero the opposite leg's current is reduced.

An amp that transitions has some quiescent current far below maximum which then is INCREASED above a certain threshold during which the opposite leg eventually shuts off.

These are the two required characteristics for a true class A:

• Maximum current and power goes through the transistors at 0V
• Neither transistor side ever fully shuts off.
  

There are a number of Class A amps which fulfill this requirement.

Of course this makes true class A amps monsters in terms of electricity consumed and heat output.

I also want to point out that it seems Luxman also does a similar thing with the L 590, but I'm not entirely sure.  They sell it as a 30WPC integrated but measurements indicate it can do much more around 100WPC.  Perhaps it is also a "high bias" class A/B?  It is also possible it is a true class A amp but can't handle the required preconditioning load so they instead underrate it.

XA60 is a great amp. 

Thanks everyone that answered my questions.  I didn't mean this as a bash against Pass, rather I was just curious as to how this all works. As I said in my original question, I'm probably going to purchase the XA60.8 so no worries at all about them doing something sinister.  

All ‘class A’ power amps transition to A/B at high levels!

Nothing sinister going on here.

Technically it is a Class A/B amp but Pass sells it as a 60 watt Class A amp and it does operate in Class A up to 60 watts.  He does this in order to distinguish it from his X series amps that operate more like traditional Class A/B amps (10 -15 watts in Class A then switch over to Class B).

Most people know this about Pass amps and give him a pass on it.  Now you know it too.  If you think this is wrong, contact Pass Labs about it.  

Indeed they are impressive.  I'm really impressed by the entire XA line, but as far as I understand, all AB amps run at some point in class A and then transition. Yes, most transition way less than 122 Watts, but I'm still confused as how a class A amp can leave class A and still be called a class A amp (Unless that's the way they all work). 

122W until leaves class A....
that is a class A amp of the highest order!

  I don’t think my brothers McCormack dna-750 monos even do any class A at all, they sound great all the time, and my Odyssey kismet amps are 10W of class A, they are very refined, and have a spectacular sound until the volume gets pretty loud, at a normal to average loud volume, the class A is great!!

 Wish I had a pair of class A amps, they are simply flawless!

 Class A is sublime!

  

Yeah, I read that too and understand that it's pure class A, but what's this transition to AB thing?  Do all class A amps have a peak transition to AB point or is this unique to Pass?

According to the man who designed it it's pure class A as is all the XA series amps. 

https://www.passlabs.com/products/xa60.8/