OT: How bad would this damage my amp?

[Drumsound]

I'm pretty sure the only thing it might do is add a little buzz to the signal while using an instrument cable insead of a speaker cable.

[Gordon Rice]

It'll take a little top end off of the signal--the longer the cable, the less top. I've always been told that it loads the amplifier down inappropriately, which is why it's a thing to be avoided. An hour and a half, though--I really can't imagine that doing any damage given that I've seen people do that night in and night out for year after year without any harm coming to their amps. They've been surprised when I pointed it out to them and astonished at the improvement in their sound when they started using the correct cable.

As I'm thinking about this, a faint bell is going off at the back of my worthless little brain: Is it more of a problem if one does that to a solid-state amp? I *think* that might be the case . . ..

Anyway, relax: Your friend may not be well-educated regarding cable types, but he didn't break anything of yours either.

--gmr

[lucey]

if the cable didn't melt - blow a transformer up ... and the amp still works, you're fine

[C/G]

Tube amps are pretty tough, your amp will be fine. Come to think of it our PA at the jam space has had a guitar cable as a speaker cable for about the last 5 years.