6sf5gt ??

[mp9]

are any of the brands of 6SF5GT better sounding as driver tube to a 2a3, i.e. arcturus vs., raytheon, ge, philco and others. any favorites or are they all basically the same?

[Miles Prower]

I'd say that the ones you mentioned are all equally lousy as drivers for a 2A3. The 6SF5 is a high gain triode that's designed to operate with very small plate currents (~1.0mA). The 6SF5, like all the other high gain triodes (12AX7, 6SL7, etc) needs to work into a Hi-Z, Lo-C load, and the grid of a power triode like the 2A3 ain't it. It isn't going to have the current sourcing capability to charge up the 2A3's Cgk + Cmiller + Cstray, and that will cause slew rate problems. The 2A3, like a great many other DHTs, is likely to start pulling grid current even before Vg goes more positive than the cathode voltage. No way will a 6SF5 be able to handle that. It'll roll over and die when a fast transient actually does drive the grid more positive than the cathode. The 6SF5 will have to work into a driver, either a cathode follower or a MOSFET source follower.

[mp9]

yeah i don't know i'm not that advanced, it's what is used in my Fi2a3's.