Full tone stack off of an EF86?

[Andy Le Blanc]

Pentodes have plate resistances in excess of 1M. A usable scale with common
values might be to replace the 250p with 50p, the .1 with .022, and the .47
with .01. The slope resistor might be 470k. The treble and bass pots could be 1M,
and the mid pot. might be 250k. The mid control gives a deep notch at the
extreme that swings from around 250 to around 1k hz . Should work with
any pentode.

[dehughes]

Some of the 65Amps models use a EF86 with a tone stack, e.g. the Soho. The topology there is EF86 - gain control - second gain stage plus cathode follower - tone stack w/ bump circuit - PI - power amp.

Nice, but I'm only working with two preamp tube spots, so that extra gain stage/follower won't fit. Interesting to hear how they do it, though...

[dehughes]

Pentodes have plate resistances in excess of 1M. A usable scale with common
values might be to replace the 250p with 50p, the .1 with .022, and the .47
with .01. The slope resistor might be 470k. The treble and bass pots could be 1M,
and the mid pot. might be 250k. The mid control gives a deep notch at the
extreme that swings from around 250 to around 1k hz . Should work with
any pentode.

AWESOME. Thanks Andy. That helps a lot... I may end up trying that in the end...