I remember now, thanks for the explanation.

It's the same as if the CT was and, and then the output was just the common point for all the power transistors.

There is a reason this works better, cheaper, probably doesn't need the level shifting transistors or something.  It's a common design.

Here is the schematic.

I have one of these with loud hum in the power amp.

Not filter caps, tried that.

Not preamp, with Poweramp In grounded, it's still there.

Moving green ground wire from pcb gnd to chassis had huge effects.  Both location of mounting lug and path of green wire made a huge difference.  It was best when just disconnected.

Other than this issue, amp seems to work fine.