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In Reply to: RE: Yes it is, but why? posted by gusser on June 30, 2008 at 11:29:31
Actually the first applications for the 300A IIRC were in theater amplifiers, (Westrex Sound System) and if you read the design notes in the original WE documentation you will see that the 300A/B was actually designed for audio power applications.I am not aware of any applications of 300A or 300B in voiceband telephony circuits other than perhaps voltage regulation. (I also admit I haven't looked that far and wide.)
The only difference I am aware of between a Western Electric 300A and a 300B is the location of the guide pin on the base.
The 300A/B were deliberately designed to be extremely linear, bear in mind they were designed at a time when most designers likely to use these tubes were not yet acquainted with Harold Black's negative feedback theory.
http://ieeexplore.ieee.org/iel5/5/31338/01457188.pdf
The 300A was introduced in 1933 and the 300B a couple of years later.
Black worked at Bell Labs and was involved in amongst other things remote transmission of high fidelity music over broadband telephone lines. In this context development of the 300A and 300B was probably driven by concerns that might arguably be the point where hifi was born. Look at development of stereo recording at Bell Labs in the 1930s as an example.
Bell Labs and Western Electric were inextricably linked as the research and manufacturing operations of the Bell System. (ATT)
Edit: a minor clarification, corrected typo
Edits: 06/30/08 06/30/08 06/30/08Follow Ups:
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