I was given one of these when I was 11. Got my first "proper" electric shock from it too - the chassis was out of the case, it was off, but plugged in. I picked it up and my thumb made contact with the rear of the power switch - there are pins that poke through the body of the switch, carrying live and neutral. Of course, the earthed chassis made it tricky to let go of it. Nasty - remember it as if it was yesterday.
I think mine might have been an earlier version than the advert shows, as the output stages were transistorised. I bought the schematics from Amstrad (for a whole £pound) - probably still have them somewhere. Sadly, I failed to fix it, and my step-dad convinced me to gut it and build my own design in the box - something else I failed to achieve. As I say, I was only 11.
Thanks for the memory
Edit: While searching around, I spotted the IC2000, which was my workshop amp when I was a teenager. This arrived with a failed output stage too, but this time I was able to fix it. Not by replacing the big amps, but by building a discrete amplifier on a piece of matrix board in place of the output PCB. I probably used the schematic from the 4000 as the basis for this. Wonder what happened to it? Happy days.