"Bill M" wrote in message
...
Richard Knoppow wrote:

The characteristics of the 50L6 are so completely
different from a 6L6

Thank you.
You're welcome:-)

FWIW, here are some common combinations of tubes used
in 5-tube AC/DC sets. These were typical but its not an
exaustive list, there were other tubes designed for series
string operation directly from the power line. In England
and in Germany other tube types were designed for the same
purposebut operating from 230/250 volt mains. In fact the
famous and rare original tube used in the famous
Telefunken/Neumann U-47 was originally intended for such
use. It was chosen because the filament could be run off the
microphone bias voltage, an economy move since it
elmininated the need for a separate DC filament supply:

C.1934, from the RCA RC-12 tube handbook:

6A7 Converter
78 Remote cut-off IF amplifier
77 Combination dual diode and triode (detector, AVC,
first audio)
43 Audio output
25Z5 Rectifier
Plus 150 ohm, 10 watt filament dropping resistor

From the RCA tube handbook RC-19 (1959)
Miniature tube types

12BE6 Converter
12BA6 Remote cut-off IF amplifier
12AV6 Combination dual diode-triode (second
detector-AVC-first audio)
50C5 Audio output
35W4 Rectifier

Two other examples:

Hallicrafters S-38B, a five tube set typical of many of the
early 1950s.

12SA7 Converter
12SK7 Remote cut-off IF amplifier/BFO
12SQ7 Combination dual diode-triode (second detector, AVC,
first audio)
50L6 Audio output
35Z5 Rectifier

The original S-38 was a six tube set with an additional
12SQ7 tube as BFO and noise limiter. In the S-38B the BFO
was obtained by allowing the IF stage to regenerate, a
circuit patented by Hallicrafters and the ANL was
eliminated. I am including the S-38 because it is an
application of the 35L6.

S-38 (c. 1949)

12SA7 Converter
12SK7 Remote cut-off IF amplifier
12SQ7, No.1 Combination dual diode-triode (second detector,
AVC, first audio)
12SQ7, No.2, BFO and Automatic Noise Limiter
35L6 Audio output
35Z5 Rectifier

Note that the filament drop here is 118V and in the five
tube circuit its 121 volts, all close enough to the 110V to
120V range for AC current at the time these sets were in
use. DC voltage was common in some cities, notably New York,
I think at around 110 volts. DC was convenient for operating
traction motors of the sort used in elevators so it was
continued until a surprizingly late date. DC was also
available in some other US cities but its beyond my recall
which ones. 110 VDC was also common on shipboard.


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Richard Knoppow
Los Angeles
WB6KBL