I got a pair of Krell KMA 100s back in the early 80s and back then they were just mono amps. The block came after. I cannot say where it originated. They were more squarish than stereo amps and instead of putting them in cabinets we stuck them on the floor either behind or between the loudspeakers. They looked like blocks so the term is not a stretch. I now have mono amps that are under the speakers and are in no way shape or form blockish. They look more like a whore house chandelier:-)
