Power MOSFETS work just like valves Peter

Speaking of which, here's the big brother of the '66, a KT88

Cossor was a very famous and revered radio and TV company that ceased to exist in 1959 when taken over by Philips...
The KT series of valves were originally made by the MO Valve Company in the UK, a part of GEC. Audiophiles and so on believe these are the very best and they command huge prices as a result... They get very agitated at these Chinese copies bearing old and well-loved British brand names...