22-10-2023, 12:15 AM
I'm hoping for virtually zero microphonics, noise way lower than any conventional pentode and amazing linearity... as have all been suggested in various threads and write up's in various places re these rod pentodes. I'd then be a very happy bunny.
Pity about the low Gm and Mu (9-12 ish as a triode and only "Mu equivalent" of something like 200 as a pentode yeah?) but you can't have everything!
Re EF86 it has been reported in various places that when triode connected it has fantastic linearity. There was in fact a data sheet for the Svetlana version with an application circuit included which claimed a rather unbelievable 0.01% THD @10V RMS out! I had to try this and can report that it's absolute bol... er.. incorrect. I tried all the ways of making it a triode, tried the Svetlana app circuit, plus a few things from on line and it's now't special at all. It made bugger all difference whether it was a Svetlana, a Mullard or whatever EF86's I had there to try (+/- 20% ish on any parameter between valves IIRC). About the same THD as an ECC81 with a little lower gain IIRC. It was a few years ago I tried this so if yer want proof or specifics you'll have to try it for yourself folks
Myth busted IMHO.
Pity about the low Gm and Mu (9-12 ish as a triode and only "Mu equivalent" of something like 200 as a pentode yeah?) but you can't have everything!
Re EF86 it has been reported in various places that when triode connected it has fantastic linearity. There was in fact a data sheet for the Svetlana version with an application circuit included which claimed a rather unbelievable 0.01% THD @10V RMS out! I had to try this and can report that it's absolute bol... er.. incorrect. I tried all the ways of making it a triode, tried the Svetlana app circuit, plus a few things from on line and it's now't special at all. It made bugger all difference whether it was a Svetlana, a Mullard or whatever EF86's I had there to try (+/- 20% ish on any parameter between valves IIRC). About the same THD as an ECC81 with a little lower gain IIRC. It was a few years ago I tried this so if yer want proof or specifics you'll have to try it for yourself folks
Myth busted IMHO.
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