From Russia with Love
The interesting combination to explore from our previous designs is to mix some western valves like 01a into the Russian parade.
The result would be quite interesting, as the sound of the 01a has proven to be amazing. Therefore 01a driving 4P1L is possible as the 4P1L doesn’t need a lot of drive. Instead of using 4P1L as a driver, we can opt for the 01a which has a similar gain. What is interesting is that the voltage swing required by 4P1L wouldn’t force the 01a outside the zone in which is highly linear, hence, with some modifications, it can work as a great driver here.
The circuit
Instead of starving the filaments of the 01a, given the voltage swing requirements for a driver, we ought to drive it at full tilt. In the circuit above, the 01a hasn’t got the stones to drive the 4P1L pair, therefore we have added a cathode follower as explained here. The M1 follower will then drive easily the output stage.
