"Barry Mann" wrote in message
om...
I think any discussion of tubes transistors and distortion should be
tempered with an appreciation of the historic shift in design
techniques.

For example, undergraduate 1950's and 1960's tube designers didn't have
Root Locus in their tool bag.

I learned root locus stability analysis in the mid-60s.

This page references a text from that time:

http://www.cbu.edu/~rprice/lectures/rootlocus.html

Coughanowr's book came out in 1965. Coughanowr received his PhD in 1956, so
any precident-setting paper was probably published in the preceeding 15 or
so years.