Tube amps known to have a low damping factor?

Which tubes amps are known to have a characteristically low damping factor, 20 or less? Which are known to have a characteristically high damping factor?
I would think it much easier to make of list of tube amps with a dampening factor higher than 20.
(Limited) damping in tube amps is not due to the power output tubes, but to the magnetic hysteresis (lag) of the power output transformers. SS amps (*most of them) where the speaker (load) is connected directly to the power output transistors, can have damping factors of 1000 or more! (Which is why SS amps are prefered for woofers and subwoofers.

* One exception I know about (in SS amps) are those McIntosh SS amps which employ an 'autoformer' at their output. If you check the specs on those, you will see they show a rather modest damping factor, just like tube amps; but again, this is due to the transformers.