Small: I have, am sitting here listening to, a Carver CUBE
https://www.hifinews.com/content/carver-m-400-cube
mine is the M-400t (t version i.e. tube sound)
This one is overpriced, but nice photos and info
https://reverb.com/item/39295847-fully-restored-carver-m-400t-the-cube-stereo-mono-power-amp-over-20...
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OP mentioned class A/B
evidently it is class A/B up to 20 wpc, which (if you watch any McIntosh meter, or the Cube's db meter while playing), is almost everything. It has non A/B tricks to deliver more power when needed.
excerpt from the hifi news review linked above
"The innermost pair operate from ±25V rails and constitute a 20W Class A/B linear output stage, and stacked on either side of this pair is another pair of output transistors, commutated or switched by catching diodes and some driver circuitry. These are linked to ±50V supply rails and accommodate the swing of signal peaks between ±25 and ±50V. A third pair, the outermost, are fed from ±80V lines, these using additional driver and bias circuitry for clean operation.
For power levels below 20W, the additional transistors and rails are never invoked, and no difference in operation from a conventional amplifier should be apparent".
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Frankly I never knew mine, t version, is supposed to sound like tubes. I bought it on Harvey's used shelf as a curiosity.
Used it for it's small size, in a bookcase with small bookcase speakers like now.
I did use it's 200 wpc with my JSE Infinite Slope Model 2's, compared it to McIntosh MC2250 SS, 250 wpc. It is astounding how that little .... can compete.