Tweet
I suppose you could also shrink tube the input resistor lead and run it and the plate lead through a small ferrite bead. Almost certainly safer than the cap to grid since there's less chance of a cap short putting HV on the input jack. If the plate and grid through a ferrite bead is too audible you could just wrap a turn or two of the plate lead around the grid lead. Probably a tiny pf value. Maybe just a fraction of one. Still no math, but just thinking out loud.
-
"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz -
I've used a 1PF from anode to grid and it usually gets rid of any oscillation issues. But I think I like the idea of the 47 PF to the cathode, just to avoid issues should the cap short out, also 1 pf are hard to come by outside of Silver Mica's=$. Didn't some Highwatts do the HV wrapped around the grid wire? or was that a Randal Smith patented thing?Comment
-
Yep, two wires twisted together is about 1-2pF per inch. Old radio hams sometimes used this as a makeshift trimmer capacitor, snipping pieces off until the right capacitance was achieved. The device was known as a "gimmick"."Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"Comment
-
I suppose one fea with the wire off the B+ is that it could couple some noise. But at the first preamp node the B+ should have little to no noise on it.Comment
-
I thought the wire came from the plate, not the B+."Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"Comment
-
Oh right, giving some NFB to the grid..Comment
Comment