Robbie wrote:

I want to put a load on small tube amps that simulates the reactive load of a
speaker, not just a resistor... I know that spk models are very complex, but a
simple circuit should be possible. I'm thinking of a regular full range spk like
a guitar amp speaker, shouldn't be too hard? I saw such a circuit before but
can't locate it.

How about... a speaker? If you don't want to disturb the
neighbors, try hiding it in the fridge. The insulation of
the fridge should muffle the sound.