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Synchrodyne · 22nd Oct 2019, 2:38 am

Thanks, Pieter, for the background.

It looks then as if the EAA91 was an unexpected complication as far as Philips/Mullard was concerned.

Presumably the third party (possibly/probably)Telefunken wanted to introduce an exact copy, physically and electrically, of the American 6AL5. Given that the EB91 designation was already taken by Philips/Mullard for a valve that was electrically similar to but physically different from the 6AL5, that third party felt that it needed a different designation, and for whatever reason it picked EAA91.

As a sidebar, I think that Telefunken may also have been the originator of the ECC85, with Philips being the follower in that case. Philips Book IIIB, which covered the FM-AM radio valves, did not mention the ECC85. Rather the EC92/UC92 was the Philips VHF radio (single) triode at that time.

Cheers,

22nd Oct 2019, 2:38 am	#45
Synchrodyne Nonode Join Date: Jan 2009 Location: Papamoa Beach, Bay of Plenty, New Zealand Posts: 2,944	Re: Why Both EAA91 and EB91? Thanks, Pieter, for the background. It looks then as if the EAA91 was an unexpected complication as far as Philips/Mullard was concerned. Presumably the third party (possibly/probably)Telefunken wanted to introduce an exact copy, physically and electrically, of the American 6AL5. Given that the EB91 designation was already taken by Philips/Mullard for a valve that was electrically similar to but physically different from the 6AL5, that third party felt that it needed a different designation, and for whatever reason it picked EAA91. As a sidebar, I think that Telefunken may also have been the originator of the ECC85, with Philips being the follower in that case. Philips Book IIIB, which covered the FM-AM radio valves, did not mention the ECC85. Rather the EC92/UC92 was the Philips VHF radio (single) triode at that time. Cheers,