you guys are right. i did post twice because i'm not to good with a computer. i did use mine from 1973 till 1989. then had it in storage till 2000. i would say there have been many amps since 1970. some are inexpensive some are not. i only bought the 400 because of the price. after reading many reviews some say it was'nt well designed. that may be true or not but i have 9k mcintosh amp now.
phase linear amplifiers
back in the early 70's I bought a phase linear 400 amp. never will buy phase linear again. in 2000. it fried 3 of my speakers. later on I read they they were known to do this. they were cheap money for the big watts but were not well designed well to work under stress. I have McIntosh now. no worrys!