Over 30 years ago, when I was a High School student, I bought a pair of headphones, but I can't remember the model. They were circumaural; same basic shape as the Senn HD580/Gxx series, but very crude and simple.
I learned that headphone jacks did not power headphones correctly, but I did not know the details. So I plugged them into my power amp, which I think at the time was a pair of Dynaco 70's running in monoblock mode.
I literally smoked those phones! There were wisps of smoke coming out, with a bad burnt odor. I never hooked headphones up to a speaker amp again. It did force me to buy a pair of Koss Pro-4AA's, which were pretty decent dyna mic phones for the day.