lots, but one one can be the best and that is New York Audio Labs, too bad they went out of business when i was like 10
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Silvaweld, Graaf and Croft are three more.
Generally OTLs seem to split along two lines: Symettrical circuitry, using a Circlotron for an output circuit, and Asymettrical, using a Totem Pole output, which looks a bit like a mu-follower circuit.
OTLs may or may not have an output coupling capacitor. Totem-Pole types usually use negative feedback, although there is at least one patent where the amplifier did not use any.
In Circlotron OTLs, negative feedback is entirely optional.
Either can be any combination of triode, tetrode or pentode, and class A, AB or B.