26-10-2023, 01:44 PM
(This post was last modified: 26-10-2023, 01:53 PM by Murphyv310.)
(26-10-2023, 12:41 PM)Kalee20 Wrote:(24-10-2023, 04:29 PM)Mike Watterson Wrote: I wonder do the old octal 1.4V Sylvania have more variable mu than the sub-miniature western types due to longer filament?
But a larger voltage drop certainly would!
Hi.
Certainly agree with this, if you remember my previous comments regarding the 1j42a a reduction in filament volts to 0.7v gives a definite change to the valves characteristics. I've even made a one valve TRF using the 1j42a running 0.7v filament and 4v HT which gives greater volume and sensitivity that 9v HT and 1.2v filament voltage. They also oscillate at higher frequencies with low filament and HT.
I actually stumbled upon this as I wanted to add filament protection to them with 2x 1N4004, one was shorted and I wondered how adding two diodes improved performance only to discover slightly below 0.7v on said filament.
