Yes, tube amps are sort of the opposite of solid state when it comes to running with no load or accidentally shorting the speaker leads (big problem for solid state, no big deal with tube gear).
Another helpful hint for someone auditioning with tubes for the first time: If you turn off the tube amp to switch things up, wait a few minutes before turning it back on. Quickly cycling from on to off to on again can cause some tube amps to misbehave. I've heard some loud crackling and I have seen rectifiers put on a light show when that is done.
Another helpful hint for someone auditioning with tubes for the first time: If you turn off the tube amp to switch things up, wait a few minutes before turning it back on. Quickly cycling from on to off to on again can cause some tube amps to misbehave. I've heard some loud crackling and I have seen rectifiers put on a light show when that is done.