So tonight for the first time in ages I only used one amp - 74 Superbass, and of course it died mid gig - no output at all.
I was using the ax8 just for effects into the amp so I grabbed another mic cable, plugged it direct into the desk and switched to a bank of presets that included amp models. Added the guitar to the monitors and carried on.
I was probably out of action for half a song and the rest of the gig was fine with a bit of tweaking as we went.
Handy to have the option of running it either way and provide a backup - normal pedals might have meant it was the end of the gig - although I'll go back to using two amps asap for extra safety.