Also ripped off out of many offices: 101A power amplifiers, the first
negative feedback/beam power power amp, first produced in 1940. AT&T
and its local companies used them for every imaginable service until
they were replaced in the '60s by Altec tube amps.


McIntosh made three different models of KS amps for Bell as well.
They are some of the best Mc's made. They all have a specially
designed bifilar opt for each model.