Safe to switch pre-amp tubes on the fly?

[iggs]

BE-100 or any other amp I guess ... what should I do when switching pre-amp tubes?

- turn the amp off completely
- put on standby
- don't worry about it and switch them while amp is on

 

[webrthomson]

- turn the amp off completely

/thread

 

[Gadzz]

Unplug also