26 Apr
2016
26 Apr
'16
12:40 p.m.
On Apr 26, 2016, at 3:07 PM, Chuck Guzis <cclist at
sydex.com> wrote:
On 04/26/2016 10:49 AM, Paul Koning wrote:
The artist who built that radio is Dutch; the tube is German (Loewe). I know of two of
these IC tubes: 2HF and 3NF, which stands for "2 stage high frequency amplifier"
(i.e., RF amplifier) and "3 stage low frequency amplifier" (i.e., audio
amplifier). In each case, these are full circuits, including all the bias resistors and
coupling elements, all enclosed within the vacuum envelope. You can see them in good
pictures: the passive elements are long skinny tubes, enclosed in glass to protect the
vacuum.
Yes, the reasoning supposedly was taxation. http://www.electricstuff.co.uk/loewe.html has
some more detail, including about some other designs along these lines: a Loewe dual
pentode plus triode, and a GEC photocell plus amplifier.
This sort of stuff doesn't seem to be all that common; I haven't seen it
elsewhere. Multiple tubes, like dual triodes or triode/heptodes are pretty common, but
those are just the active part.
paul
That tube is interesting: it's the
world's first integrated circuit.
Yes, a hollow state integrated circuit. I describe it that way
because it is a complete subsystem (in this case, a complete 3 stage
audio amplifier) rather than just something like a dual-triode tube
where the connecting components are still external.
Reminds me of the time I got my hands on a 1940s 3A8GT - battery
pentode, triode, double diode in one envelope. Not nearly as
interesting as the one in in the Dutch model, though.
What was the highest level of integration in a single envelope? I seem
to recall that some of the European taxes were based on the number of
tubes in a radio, so there was a strong impetus to integrate.