Changes to Fet Valve amplifiers over the years,
Changed to our own purpose designed metal chassis and complete internal layout design with new circuit board. Changed tube type used.
Went from Hitachi output mosfets to Exicon mosfets,
Upgraded to Exicon double die mosfets.
Added regulated power supplies for small signal circuits.
Added regulated output transistors power supplies.
Redesigned all internal circuits boards to provide adjustable regulated power supplies providing best performance independent of parts variations,
Major internal overall layout redesign improving noise and signal path quality.
We keep learning and making our products better but rarely announce design upgrades any more.