So I had an audition tonight. Thought I would take one last run through the material and suddenly no sound. Checked all the obvious stuff (chords, fuses, changed outlets). The light is on but no sound. If you unplug the chord from the bass and touch the end you still get the crackel and if you turn the gain all the way up you can hear the bass faintly. I had this amp for 8 years, it's survived drunks spilling beer on it and countless gigs in hot enviroments. And it picks tonight to crap out.
Are you sure it's the amp? If you still get noise when you touch the cord that's going into the amp it sounds like the amp is still working.
I had the same experience with another manufacturers amp. It turned out to be a pre amp pcb fault. You haven't mentioned which amp you have? If it's an LH series then the tube could be worth swapping as that's an easy thing to try.
Run backup equipment, or go DI and monitor...if worse comes to worse, borrow from a trusted friend or rent an amp from a local music store?
Let us know what you find out! I have ha5500 that survived a tumble out of a truck with only a sheared shaft. No issues after 10 years or so!
if the amp has an Effects Loop link send and return with a signal cable. Same for pre-amp out power amp in jacks.
If it's a head/cab rig, try subbing out the cable from the head to the cab. It's possible that there's only a few angel hair strands trying to do all the work. The preamp tube as said before may also be the culprit. Failing those as the problem, scramble to borrow from a friend and get the Hartke to a trusted repair shop.