Today, while reading the section "Valve Numbering Systems" on page
11 of the "Radiotron Designer's Handbook" (4th ed), I came across
something that seems a bit puzzling. I thought I understood what
they meant until I checked out the two web links for the examples
listed (below).
quote
The second symbol is a letter which is allotted in sequence
commencing with A, except that I and O are not used; rectifiers
follow the sequence backwards commencing at Z. When all the single
letters of a group are exhausted, the system then proceeds with two
letters commencing with AB; combinations of identical letters are
not normally used.
***
The single-ended a.c. range has a first letter S while the second
letter may be that of the nearest equivalent in the double-ended
range -- e.g. type 6SK7 is the nearest single-ended equivalent to
type 6K7.
***
/quote
Apart from some small differences in parameters and pins, I see very
little difference between these two examples (6SK7 vs 6K7)
http://www.mif.pg.gda.pl/homepages/f.../001/6/6K7.gif
http://oldradio.qrz.ru/tubes/foreign/01/6SK7.gif
In what sense is the text referring to single vs double-ended? What
seems suspicious to me is the use of "double-ended range". Can
someone clarify what exactly they meant by this?
Thanks
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