Ed - I think the Russian caps in Fran's amp came from you,
via Shannon to me when I built a couple of the early g*s*g's.
... tom
They may well have originated from me, I've done so much "hoss trading" here and over at NNETG, over the past years that I have lost track of who got what and when
The big K40y-9 caps are OK, there is no real reason to change them out, unless you want to try other brands and makes. I've used some significantly oversized caps in some of my builds, like the big 0.1 uF / 500V teflon caps, which are nearly the size and weight of D cell batteries
The green "kommie kaps" are also somewhat oversized, about the same diameter, but half again as long as the 0.1 uF K40y-9s. These "green meanies" are polyprop in oil, not paper in oil. Still good sounding, and I still have LOTS of them, though I have used up all my K40y-9s. (the Russian letter
y is really a
u, so these would be called back in the motherland, K40u-9s.
The "outer foil" end is allegedly indicated by the little symbol in front of "400B". Which, in your board, would be the ends of the caps closest to the 270K resistors, R9 and R10.
0.22 uF instead of 0.1uF would theoretically extend the lower frequency response by an octave, but the ultimate limiting factor would be the OPTs.
THe operating voltage would have no effect as long as it is at least high enough to withstand the existing circuit voltages.
HTH
/ed B