Originally Posted by
Firebottle
Going the hybrid route and using FETs, particularly in the power supply circuitry, is a designers wet dream.
Put simply the characteristics of power FETs is like a valve on steroids, so you get whatever benefits accrue from using valves but with much better performance, there is also the simplification of no heater required.
The individual heater regulators are a bit OTT possibly, as I wouldn't expect any crosstalk between stages via the individual heaters. However it does make any fault protection or fault finding that much easier.
:)