[78-L] Our second phonograph

[Steven C. Barr]

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From: "Royal Pemberton" <ampex354 at gmail.com>
> One early set I saw had three 26s, one 27, two 71As and an 80.  The 24 was
> the first screen grid tube, introduced in 1928.  The later tube numbering
> code that gave us numbers like 2A3 and 6L6 didn't arrive until the early
> 1930s (1932 or 1933).
>
71A's (and, I assume, 71's) were among the very first "power tubes," which
appeared c. 1923-24, and served as audio output stages once radios had
"loudspeakers" rather than earphones. The *80's were used as rectifiers
once radios were no longer battery-powered and needed direct-current
supply voltages; they survived well into the era of tube numbering (how
can one improve on a simple rectifier tube...?!). They would be replaced
by the near-ubiquitous 5Y3 (rectifiers were "lettered" downward from
"Z"!)...with the 5U4 becoming ubiquitous in higher-powered radio sets
in the later thirties and forties!

VERY early radios used *01A" triodes, cascaded. IIRC, these were replaced
by *26 triodes?!

Steven C. Barr