I very stupidly did that… It was a few months before I realized it, and since it had been a very long time (over 2 years) since I used the Small Clone, I can’t really tell if it was damaged (I don’t remember what it sounded like before I plugged in the adapter I’d been using for my Proco Rat, the power adapter of which is positive center).

tl;dr

will damage always result from plugging a positive tip adapter into a negative center jack?