Pass....Accuphase....or......

@southofdallas "How much class-A power does the A-48 deliver before drifting into AB?"

Theoretically A48s always will be in class A mode for full power range, using resistive 8 Ohms load.. BUT, :-), speakers are not resistors, loading applied to the amp is complex / resonating load, at some frequencies much lower effective impedance than rated! For sure A48s becomes high-bias AB class amp with 4 / 2 Ohm rated speakers..

“How much class-A power does the A-48 deliver before drifting into AB”
@southofdallas 
This is why it is crucial to properly match an amp to your speakers and vice-versa. If your speakers dip well below 8 ohms in certain frequency ranges, the P-4600 might be a better choice since it’s designed to handle lower impedances more efficiently while still maintaining excellent sonic 

While the A48s is designed as a Class A amplifier under an 8-ohm resistive load, real-world speakers present a much more complex and dynamic impedance profile. As the impedance dips below 8 ohms, especially with reactive loads from crossovers, voice coils, and cabinet resonances. the amplifier is forced to supply significantly more current.

@westcoastaudiophile @lalitk If I look at the specs it seems to me that the A-48 is the more stable of the two. Doubling the output power down to 1 ohm.  On paper, it does not have a problem with low impedance. Right?

@southofdallas correct! A48 will be more stable at lower load impedance than P4600, which has higher supply voltage.

@lalitk "While the A48s is designed as a Class A amplifier under an 8-ohm resistive load” probably typo, A48 is designed as class A amp for loads = or > than 8 Ohms. for loads < 8 Ohms it is a high-bias AB class amp. 

A48 is designed as class A amp for loads = or > than 8 Ohms. for loads < 8 Ohms it is a high-bias AB class amp. 

To be clear, 'high bias' class AB amp isn't a thing. Its either class A or its class AB. In this case, class AB. Any properly designed class AB amp will not have an audible 'transition' from A to the B region.