Thanks for saying that Tubelab. I've been feeling a little bit overwhelmed.
I re-centered myself yesterday.
The reason that I asked about self-split cascode is because I (like everyone else, seemingly) want to build a low-watt push-pull guitar amp that doesn't sacrifice any tone.
But that's only about half of what I've been planning to build, and I think that I should compromise on the power amp.
My idea is to shove a Firefly and a Champ into a single box. I'm not looking to make a 2-channel amp. I want two completely different signal paths - driving different speakers. Bi-amping is an important part of the idea.
I want to plug my guitar into a shared 1/4" input jack, split the signal to separate pre-amps, then send each pre-amp through independent series f/x loops and on to independent power amps, independent OTs and independent speaker outs.
I want one side to be fairly clean and have a bit of headroom. (I envision that as the champ side). I have a preamp schematic that starts with a Pentode in V1, gain pot, then into a cathode follower, then a Fender-ish tone stack and volume pot, gain recovery, f/x loop, then a single 6V6. 3 tubes in all and something like 5 watts.
I want the other side to have cascading gain stages with two gain pots as well as a volume pot and tone stack. Then I want that to drive a push-pull output section that puts out very low watts. I don't know how much I need, but I want it to be about as loud (dimed) as the other side is when it's still clean. (I was figuring 5 watts to 1 watt might be about right)
If everything goes well, then I ought to be able to cross-connect the power amps (via the f/x loops) and send the "clean" preamp signal to the push-pull power amp, and vice-versa.
I'm excited about the idea but I'm not sure if there are some hidden barriers that could de-rail the project, and I'm not entirely satisfied with the idea of using push-pull triodes in the output. Pentodes definitely beat triodes for sound imo.
But I'm also trying (as a design challenge) to use only current production tubes. I was really really tempted by the ECL84/6FP4 as I said - but it's not being produced.
So I'm either going to have to use EL84s - which would be too loud - or ECL84s - which aren't being made anymore - or perhaps something that I overlooked - or I can just use the 12au7a.
12au7a is probably my best bet.