24-10-2023, 04:29 PM
(This post was last modified: 24-10-2023, 04:32 PM by Mike Watterson.)
I wonder do the old octal 1.4V Sylvania have more variable mu than the sub-miniature western types due to longer filament?
Also the earlier battery valves came in 2, 4 and 6V versions originally. Philips seems at one stage to have promoted the 6V types (actually close to 7 V on a freshly charged battery) and then for battery the 2V system won. The 4V survived on mains sets, both indirect and direct filament rectifiers and power out triodes.
I agree than on rod pentodes filament polarity makes no difference as would be expected from symmetrical construction.
Also the earlier battery valves came in 2, 4 and 6V versions originally. Philips seems at one stage to have promoted the 6V types (actually close to 7 V on a freshly charged battery) and then for battery the 2V system won. The 4V survived on mains sets, both indirect and direct filament rectifiers and power out triodes.
I agree than on rod pentodes filament polarity makes no difference as would be expected from symmetrical construction.
