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In Reply to: RE: Since we were talking about NOS vs new production tubes posted by SETdude on June 07, 2016 at 05:53:44
"Is it possible that the technology and knowledge necessary to refine the performance of modern-made tubes may still be secret to some degree?"
Yes.The EI KT90 is a perfect example of this. That tube is a phenom in itself and once the skilled craftsmen left after the war broke out in the Yugoslavia,the new people that came in to build the same tube with the same materials,couldn't do it.The tube had misaligned grids and would arc over and just didn't sound nearly as good IMHO.
"The old production tubes that are revered today are being used in circuits will 'better' parts and many were designed for TV not audio."
The 6SN7 and the 6CG7 were originally designed as vertical deflection amplifiers or as horizontal oscillators and yet we use them so much in audio. We are finding that if tubes have a wide bandwidth,they will be able to handle audio frequencies quite well in most cases.
Tubes like the 300b,211,and 845,those were used in RF applications.Most tubes we use in audio were not designed just for audio,but as general purpose wider bandwidth amplifiers. They even used 300b tubes as rectifiers in some cases.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/08/16Follow Ups:
There has been no war in what is now the Czech Republic since WW2, unless you count the 1968 uprising. The EI factory was in the former Jugoslavia.
My error and you are correct. Thanks. I got a war right but I thinking the wrong country because you don't often see tubes from Yugoslavia anymore.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
the 6SN7GTA and GTB were designed for use in vertical deflection amps and horizontal oscillators. The original 6SN7 was designed in the late 1930s, before there was a TV industry. My reprint of the 1940 RCA manual says the 6SN7 was designed for use as a resistance-coupled amplifier and phase inverter. The 6FQ7 and 6CG7 were designed as nine pin miniature substitutes (read: cheaper) for the 6SN7 and were specified for vert deflection amps and horizontal oscillators and apparently worked in B&W TVs but weren't high enough voltage and power for color TVs
They did use 6CG7s in color sets..RCA used them for the horizontal oscillator to drive the 6LQ6s in all of their tube color sets from 1960 on right up to the last one which was a CTC39x as I remember.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
My point is that the good old tubes are pretty much gone, especially power tubes, and the new production keeps improving.
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