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RE: A tube journey with lesson learned, Re; KT88 & KT150

"screen drive demanded high current drivers meaning you needed solid state drivers for maximum output."

nothing at all wrong with mosfets for driving grids at high voltage swings.

Here in front of me I have a pair of 1949 made AB2 amps. wiht originally 807 pairs in. I converted it to KT8 but seemed to make no difference to the sound.

The G1 drive which can push it to +18V positive comes from 6SN7 cathode follower.
Setting the bias properly for that is quite hard and the 6SN7 gets very hot.
If you have 300V aligned grids like in the 807 it's impossible to run screen drive.

The only reason why sweep tubes work, is because the tolerances and build quality are legendary, combined with a 1.5A-2A heater with monster cathodes to make relatively low impedance devices.
This makes the g1-g2 gain totally different and the curves far more linear.
There are also winding advantages with transformers with 1-2K anode loads + low voltages, like used in Geloso 100W amps and the hi gain EL520 range.

The KT66 and KT88 series have had their day,- that was in Reeves 100, 200W amps of the 1970s-80s.
They still work in Guitar amps as do the 6L6GC.
That's where they should continue to live and die, so who cares when they blow up!

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