When the PB-300 is linked from a Flightcase or similar PJB combo, is the extension cab's volume control slaved to the Flightcase? Or do you need to adjust two volume controls - one for each cab?
The PB300 is connected to any other amp from a line out of the other amp/preamp. It is basically just a big powered speaker. It reacts to the volume changes of the input signal just like any such device would, but also has a master volume control on the back. This allows the user to blend the amount of master amp to slave amp heard on stage when the master amp has its own speakers.