> On Apr 26, 2016, at 3:07 PM, Chuck Guzis <ccl...@sydex.com> wrote: > > On 04/26/2016 10:49 AM, Paul Koning wrote: > >> 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.
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
