I have had a AI linestage (Modulus) since the last millenium.
I got some new tubes for it, but mostly just to try them… it sounds just dandy as it is, but the tubes are almost 1/4 century old.
It is an inverting preamp, so at some point one needs to flip the wires, like as is shown on the avatar with the red and black switched up.
I have seen AI listed as used equipment occasionally.