Tube electronics have the most wonderful smell too 
They always smelled kind of electricky and of burnt dust. A definite unique smell.
My sister has the hi-fi that Dad made for the adults. Our small hi-fi was always put on the porch on New Years Eve, the 1812 Overture put on and the volume cranked up to the max. The record we had used actual cannons of the type used in the seige of Moscow, so the sound was not only authentic, but deafening. Somewhere along the line the hi-fi vanished.
Tubes create ozone as does lightning.
If there is dust on your tube gear, then you are smelling something like what happens just before a lightning storm; enhanced amounts of ozone in your local space polarising the dust in the air around you. This makes some atoms attract to each other, allowing them to collect in quantities large enough to stimulate your olfactory senses.
It is a simple thing, actually.
I can assure you that there is no dust on any of my tube gear. Dust would also affect the sound, which would defeat the purpose of going minimalist. Random amounts of dust everywhere, reacting with all the other magnetic fields in the area would become a greatly undefinable variable while listening to high resolution stereo. I could not tolerate this.
