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

I'm looking at possibly purchasing the Pass Labs Xa60.8, but am puzzled by one of its specifications.  One reviewer stated that "The XA60.8 doesn’t leave pure Class A until it reaches 122 peak watts. Then it moves into Class AB for unheard of headroom for a 60-watt amp".  I've confirmed this headroom is on the specification sheet, but if the amp actually can transition into A/B, shouldn't it really be called class A/B?  Also, I'm confused as to if this headroom is available as continuous watts or just peak.  Can anyone clarify?
dfairc777a
twoleftears's avatar
twoleftears
5,318 posts
 
Let's think about it the other way round.

How many amps described as class A/B offer 122w of class A power?
kijanki's avatar
kijanki
4,428 posts
 
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?
charles1dad's avatar
charles1dad
10,250 posts
 
Could possibly/ likely be 60 watts of class A into 8 ohms and 120 watts class A into a 4 ohm load.
Charles 
charles1dad's avatar
charles1dad
10,250 posts
 
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 
dfairc777a OP
60 posts
 
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.
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