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Old 29th Nov 2022, 11:12 pm   #21
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Papamoa Beach, Bay of Plenty, New Zealand
Posts: 2,943
Default Re: Combined power-pentode and double-diodes?

The 6BV7 double diode output pentode appears to have been an AWV own development in the absence of a suitable valve from either RCA or Osram. Given that it could have gone either the “EBF” or “EBL” route, it is reasonable to assume that its choice of “EBL” was considered and deliberate, and not just happenstance.

Possibly to some extent it wanted to do differently to Philips, who had added the 6N7 (EBF80) to its “Innoval” range late 1950/early 1951, and followed it with the 6AD8 early in 1952. In the latter, the pentode was configured for used in the reflex mode as both an IF and an AF amplifier.

In respect of the 6BV7, AWV did make the observation: “The location of the diodes in the output valve allows a very convenient layout of the conventional 4 valve straight or reflexed receiver and enables higher i-f gain to be obtained without excessive regeneration, or without neutralizing, than is possible when the diodes are located in the i-f amplifier valve.”

(Neutralization in EAF and EBF type valves was discussed by Langford-Smith, pp.1066,7 in the Classic edition.)

Doing differently to Philips per se was probably not the only motivation, though. For example, just previously AWV had introduced the 6AE7 (Osram X79) triode-heptode frequency changer to run alongside its standard 6BE6. Evidently it was feeling the heat of the competition, Philips having introduced the 6AN7 (ECH80) as one of its first Innovals late 1949/early 1950. Clearly, there was a significant part of the market that saw the triode hexode/heptode as superior to the pentagrid frequency changer, so that in this case AWV had to follow Philips and offer this type. (The 6AE8 was probably a bit better than the 6AN7, though.)


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