This was my 71a DHT preamp incarnation. I reused existing circuitry so it can be improved. Firstly the top BSP129 should be an DN2540 with heatsink. P1 can be replaced with a LND150 depletion MOSFET CCS and a resistor divider to improve the frequency response. R5 should be your preferred 100K stepped attenuator instead.
I enjoyed this very much and will definitely encourage everyone to build it. I recall that the bass response wasn’t as good as the 4P1L despite anode resistance being low as well.
Slight filament starvation to reduce microphony and DC regulation is provided by Rod Coleman boards.
Globe 71 are difficult to get hold of, but worth trying them.
Here are my earlier impressions and description of the circuit.