One possible method would be to use one ST35 board per channel, and use one channel of the VA and PI to drive both pairs of EL84s, into an OPT with a 4K primary, to the appropriate secondary impedance value (4, 5, 6, 8, 10 ohms, as required). THis would use the adjustable cathode biasing, and would be a relatively easy approach.
One PA774 and the PSU components would power a PPP monoblock channel with 4 EL84s. There is a 240VAC/50Hz primary version of PA774, I don't recall the model number (from Triode Electronics).
I have been thinking along building up PPP 35WPC monoblocks (or dual mono) along similar lines, but using a slightly modified "Poseidon" VA / LTPI board for each channel, driving 4 PPP EL84s, in fixed bias mode. I already have two very nice 4K:8 ohm "1773" OPTs, and two PA774s.
This would be electrically very similar to the design of the Manley "Stingray" orVTL TT25s, but with a lot less exotic mechanical design demands.
All I need is time and a good shot of motivation
I could go with everything on one very large chassis, with separate dual mono channels ( this would be a heavy beastie) or go with two smaller (8X12X3 inch steel Hammond chassis) which would be easier to handle and apply.
HTH
And now for something completely different...
A somewhat "loony" alternate to this design idea, of which I have worked out the details of the necessary circuitry, is a UL PSET using four EL84s in parallel, driving a Hammond 1627 or One Electron UBT-1, and using a 6CG7 SRPP driver stage. This would have lower output power - about 8 WPC in triode strapped mode, and 12 watts in UL, with a very low 2HD and 3HD figure, and which could conceivably give a 300B SET a good run for its money, at a much lower cost. I have all the necessary parts for this approach, too
/ed B