David Looser wrote:

"Arny Krueger" wrote
wrote

Most people don't realize that sound reproduction was the
equivalent of the "space race" during the 1920's and
30's. Most every topology, circuit, and interconnection
methodology can be directly traced back to the work of
Bell Labs and their competitors, much of it for military
applications.

True for analog and tubes, but not true for SS and digital.

Not even true for "analog and tubes".

Absolutely definitely not true for sure.

Even NFB hadn't been 'invented' back then IIRC, so circuits ran open-loop
with truly horrible levels of distortion.

Graham