Here is another magazine item about the release of the Philips Innoval valve range in Australia, in this case from “Radio and Hobbies” 1950 January:
There was recognition by Philips that it was using the standard noval base, but it claimed to be using a special sealing method, not requiring very high temperatures, that achieved greater accuracy and rigidity of the internal structure. One could deduce that Philips saw that feature as justifying the “Innoval” name.
Philips also stated: “Since the miniature 7-pin base is inadequate for certain types of valve, the adoption of the standard 9-pin Noval base appears to be a very logical step.”
When it introduced the Rimlock series, Philips stated that the 8-pin base covered the majority of domestic receiving applications, including the triode hexode/heptode frequency changer, which the B7G base did not. It also said that for the very valves few that required 9 pins, the established B9G base would be used. The more complex valves required for emerging TV and FM applications soon showed that 9 pins would be required quite often, not just occasionally.
The “Innoval for everything domestic receiving” approach contrasted with the American approach, which was to use the noval base only for miniature valves that required 8 or 9 pins (and occasionally, for those that required a slightly larger bulb than was standard for the B7G type). The B7G base was used for miniature valve that did not require more than 7 pins.
(In the immediate post-WWII era, it was evidently the American plan was that where the B7G base was inadequate, the octal base, with a top-cap as needed, would be used. Hence in that short pre-noval period there were some new octal small-signal releases, such as the 6S8 triple-diode triode and 6SB7Y higher performance pentagrid, which were supplanted by corresponding noval issues within a couple of years.)
As noted upthread, Philips did depart from the “Innoval for everything domestic receiving” approach in the case of the double-diode, where the B7G EB91/6AL5 was pulled into the range. (And there were some later B7G deviations, such as the EF97, EF98 and EH90.)
Here is an early Philips advertisement for its Innoval range:
And a magazine item, from Radio and Hobbies 1952 March:
This announced three additions to the Innoval range, namely the 6AD8 double-diode pentode (different to the 6N8/EBF80), the 6V4 rectifier (EZ80) and the 6BH5 (EF80) RF pentode.
The 6AD8 may have been an Australia-only issue. The pentode part had low gm (1.1 mA/V) and the valve was said to be suitable for use in reflex receivers. From that I should infer that low gm was preferable when reflexing – perhaps for adequate stability when one valve is simultaneously amplifying IF and AF?
The EZ80 was registered as the 6V4 on 1949 April 19. So this was another Philips noval valve that was evidently held back for several years in the UK and Europe, in favour of the EZ40.
The 6BH5, with a gm of 2.2 mA/V, was said to have been configured to meet expected performance characteristics in Australia. But the 6BH5/EF80 was none other than the EF41 on a noval base, retaining the internal suppressor grid-to-cathode connection. So that was a bit of exaggeration on Philips’ part. Also, by then, AWV was offering the 6BA6 with a gm closer to 4 mA/V. So maybe Philips was endeavouring to head-off any questions as to why its new RF pentode was not similarly configured.
AWV appears to have had a major influence in the Australian market. This item from Radio and Hobbies 1949 September covers its 1949-50 domestic receiving range, inclusive of several B7G miniatures, but no novals:
This advertisement from Radio and Hobbies 1952 September covers the addition of the 6BV7 and 6AE8, both on the noval base. As all of the other valves listed therein were of the B7G type, the two featured may have been AWV’s first domestic receiving novals.
The 6BV7 double-diode output pentode was an AWV own-design. So by 1952 third quarter, three distinct noval double-diode pentodes were available from Australian manufacture, namely the 6N8, 6AD8 and 6BV7.
As already noted, the 6AE8 was the Osram X79. An interesting point was that AWV chose to register it to obtain an American designation, something that it had not done with its predecessor, the X61M. The 6AE8/X79 looks to have been a very competent triode heptode. Its conversion conductance was similar to that of the ECH81 (6AJ8). It differed from the latter in having an internal connection between the triode grid and the heptode injection grid, whereas the ECH81 had an external connection. How it compared noise-wise I don’t know, but I’d guess that it was similar. I have the impression that in Australia, the 6AE8 was widely used through to the end of the valve era, whereas in the UK, the ECH81 more-or-less swept all before it, including the X79.
The X79 itself was simply a rebased X78, which being on a B7G base, required a common pinout for its cathode and one side of the heater, a rather awkward arrangement, and a consequence of Osram’s having chosen the B7G rather than say the Rimlock base for its initial miniature receiving range. Its primary “77” series frequency changer was the X77 (later X727)/6BE6 pentagrid, but it also needed a triode heptode to address the UK setmaker majority preference, hence the X78 in the short pre-noval period.
Cheers,