21-10-2023, 10:38 PM
(21-10-2023, 08:54 AM)Mike Watterson Wrote:(21-10-2023, 08:31 AM)Kalee20 Wrote:(21-10-2023, 08:10 AM)Mike Watterson Wrote: Certainly real Pentodes are inherently noisier than Triodes, but the Rod Pentode is just electrostatic rod focusing, no spiral wire grids, so is much quieter.
I'd dispute that, though - g2 in the rod pentode does draw some current, so partition noise is possible.
It doesn't matter if g2 is rods, wire spiral, or perforated mesh - if it draws current, the noise mechanism is there!
(I'd concede that the current is less, proportionally, to anode current than in spiral grid pentodes, so the actual noise may be a few db less. But it's still there)
Yes, still noise. But Joe Sousa claims that in theory and practice it's less on a Rod Pentode than a regular kind. I've also no idea why the EF37 and EF86 were claimed to be low noise, but Jez is first person I've read claiming an EF86 isn't, or pointless. Maybe I could measure but I'd take Joe's statements.
I wrote "quieter", not quiet.
Got it - yes you did write "quieter" and I read this in your post (which I quoted) as quieter than a triode. Which I certainly couldn't accept!
But I could believe that they're quieter than conventional spiral-grid pentodes.
My rod-pentode superhet is fairly quiet as far as background noise is concerned.
I've not tried any really low-level work with RP's. I do have an aim to build a magnetic pick-up pre-amp with them some day... I've made one with triodes (ECC83); with EF86 and 1/2 ECC83 (sorry, Jez!), but not these. Another is a tape head amplifier.
I've not had any problems with microphony... after all, they were designed to be fired from a gun...
