CRINGE!!! :eek:

If that's a tube amp, iamthe_eggman, you've been a bad, bad, boy! :mad:

For a transistor amp, driving a headphone instead of a speaker is no problem. :)

A tube amp [u]must[/u] have a load that is matched to the amp output. That's why they have output tranformers with several impedance settings. I've never tried it, but I think it should be possible to add a headphone output, provided you also connect a suitable "dummy load" to absorb most of the output power. Unless the dummy load can simulate the electrical characteristics of the speakers, there will be some noticeable differences in the sound you get in the headphone.