Anyway, my plan here is to build two high gain pres in a 2 U chassis that I had already started the basic machining on. I have a custom wound toroidal PT (from toroidy.pl - check them out, great custom winds and super low prices) which is conservatively spec'd to run 6 preamp tubes and a whole bunch of relays without breaking a sweat. B+ at the filter will be around 400VDC so I can build some very modern sounding preamps, which is the plan.
Here is the chassis.
Preamp A is going to be loosely based on the VHT D60. The schem here doesn't show the less/more switch which bypasses the 3rd stage or the local NFB loop switch to change the mids/feel.
Preamp B is more or less a Splawn Nitro but with a post tonestack MV. I'll likely add options to switch the 2nd stage cathode resistor from 1k5 to 3k to also to reduce the gain a bit by adding an 82k//1n in parallel to the 220k in the 2nd stage attenuation network.
The above also shows an idea for a transparent high voltage MOSFET output buffer using an IRF820. This still needs a bit more work in LTSpice to get right. I'm not super confident designing with MOSFETs yet, but there is only one way to learn and if they they the magic smoke out then who cares? I may well go with a tube output buffer as below though.
Down the line when I'm happy with the circuits I may tap off the 12VDC regulated supply for the LED and relays to power a small solid state poweramp board so I can run into a cab. A 1W class D board is tiny, although I may opt to stick with a more conventional AB MOSFET power amp board depending on what sounds best.
I can't help with that really I'm afraid. I couldn't commit to anything being built in a half way reasonable time frame and shipping to the states would be a fairly daunting prospect!
