Currently using a Samson 120a as power amp for home use. Class AB. Rated at 120 watts into 8 ohms bridged. It works well in that context because it doesn’t have a fan, so I can leave it in through my work day and go back and forth from work to guitar without white noise when not playing. I can get it to run out of gas, though, even playing my shit John Schofield impersonations in my 12x12 room at “probably not good for my ears, but not going to wake up ringing either” volume levels. At some point, it does that strange phenomenon described in the OP of getting louder, but sounding smaller.
I keep my PS170 for times when I’ll be jamming with drummer and/or drum and bass player and MAYBE a full quartet. Because despite only being rated at 170 watts into 4 ohms (my speaker cab is 8), it stays big sounding to MUCH higher volume levels than the Samson. Also weighs a lot less and I can tuck. It in the back of the cab to make transport easier. Class D.
I could start making up weird nonsense about Class D vs AB. Or I could go with Ocamm’s razor: despite what the spec sheet says, the PS-170 can deliver more power in the way a guitar needs it than the Samson. Not because of the technology of its active components, but because of the size/number of them. After all, the Samson is pretty small and light by AB standards with pretty modest toroidal transformer.
