The first gain stage (6SJ7) is the pentode and biased it according to RCA charts and the same as previous builds.Higher value cathode bypass capacitor increase gain because it decrease local feedback and cathode does not follow drive signal too much which would decrease actual drive which there is needed between cathode and control grid.
Without drawing loadline I am quessing that perhaps you have biased that pentode driver tube too hot when its anode voltage is less than 100V and it limit its gain? Sometimes tube datasheets have tables for several voltages and anode and cathode resistors and what the gain and output impedance then come.
The triode wired pentode (6SK7) was the one with a rather cold Bias I think.
My main problem now is the 6SK7. Will do more reading. I think I should just increase the cathode resistor a bit more. There is a 4.7k now with a Rp 150K. Ether lower Rp to 100K or further increase the Rk will probably get the Vp>100.
I would like it to have the desired output without the bypass cap. On the finishing stretch.
Edit. I can’t decide what to do with the driver 6SK7. Ether go for a lower Rp like 33-47K and a Rk of 1.2-2.2K or Rp of 100-150K with a Rk of >4.6K. Probably the latter. Will have to try and listen.
Or accepting that I have to bite the dust and use 6J5 with a known characteristic.