I just built an amp using the 6K5 to drive a JJ 2A3-40. Mine is direct coupled with a CCS set at 1.3mA as a plate load for the 6K5. I used a 3k ohm cathode resistor on the 2A3 to bring the grid up to 155V which is, naturally, the plate voltage of the 6K5. The plate voltage of the 2A3-40 is 300V and the bias -65V. B+ is just over 500V.