Thanks for that, I suspected as much. There was a bit of an urban legend going around among rookie musos when I first started out that playing bass through a guitar amp would damage the guitar amp. I never understood why that might be - it is just an audio signal passing through an amp.

Hypothetical situation:
You're roped into filling in on bass in your mate's band. Available for you to plug into onstage is:
  • a 50watt solid state bass practice amp
  • a Marshall JTM45


...what do you do?