The discussion about the effects of screen resistors on a 5E3 made me think about this: what if we introduced an EF86 (or other small signal pentode) before a 12AU7/12BH7 power amp to get some of that pentode overdrive that these can't deliver on their own? For example, this amp I'm working on (see schem below) is a 5W version of a 20W amp I built last year (except the 20W had a LTPI thanks to an extra preamp tube, what is cathodyne on this schematic was a post FX Loop recovery stage, the loop was MOSFET driven). Now, I'm thinking, what if I introduce an EF86 after the tone stack but before the cathodyne? Of course, that's going to be a hell lot of gain and I'll have to dump a lot of it. Or... hear me out here... what if I followed the EF86 with an interstage transformer that would act as a phase inverter? Or maybe I'm just crazy and this won't do what I'm thinking it would. Even thought about just using a dual EF86 power amp into a dummy load then drive the speaker with a Class-D module.