Ultralinear tube amps

[Helmholtz]

It is not that some transformers are more linear than others as, in having lower distortion, itīs not "better transformers" here, but "better circuit operation".

See above.

Not sure if the inventor was aware of the negative screen feedback effect:
https://patents.google.com/patent/US2710312A/en

Of course marketing always needs a catchy name.

I assume that different tubes (particularly pentodes vs beam tetrodes) have different optimum tap ratios.

[SoulFetish]

(Note to self: dial it back on the bone dry delivery.)

[g1]

(Note to self: dial it back on the bone dry delivery.)

I'm always looking for a 'straight-faced' emoji, but none to be found here.

[Helmholtz]

Some additional info on UL operation/performance contained here:
https://frank.pocnet.net/sheets/084/k/KT88_GEC.pdf

In the document part called "Circuit Supplement" there is a chart (Fig. 1) showing that performance doesn't vary really much between 20% and 50% screen tapping points, optimum being between 30% to 40%.

Seems the principle of UL operation was actually invented much earlier than the Hafler patent:
http://www.oestex.com/tubes/acro.html