Either of the de Lisle switchers should work with some caveats. You have to observe proper impedance matching between amp and speaker, or you can blow an amp output transformer on a tube amp. Also, you can’t simply turn on all your amps, ready to output to the speaker, and use a passive switcher to switch between them, because that will blow some output transformers on your tube amps. You have to observe a specific procedure, doing things in the correct order, to keep from blowing up your amps.
Tube amps need to have a speaker-type load or they blow an output transformer. Therefore, with a passive switching box, amps have to be put in bypass, or off, before you change the switcher to a different amp.
If you get mixed up, with the switcher, select the wrong amp, it’s pretty easy to blow up an amp. If you forget to switch an amp to bypass, or off, before using the selector to switch amps, you will likely blow up an amp.
You have to be careful about impedance matching between amps and cab. Tube amps are very sensitive to impedance mismatches. If you use the 16 ohm output of an amp head into an 8 ohm cabinet, or a 4 ohm cab, it can blow the output transformer. If you use the 8 ohm output of an amp into a 4 ohm cab, it can blow the output transformer. Impedance mismatches the other direction are safe, example, 4 ohm amp output to 8 ohm cab, or 16 ohm cab. Also 8 ohm amp output to a 16 ohm cab is safe.
I thought about getting a passive switcher to make it convenient to switch between different amps and different cabs. However, the convenience also makes it easier to blow up an amp by making a simple mistake. The active boxes, with protections built into them, are safer, but more expensive.
I opted for adding labels with cab ohm ratings to my wires. I have to turn amps to bypass, or off, manually unplug, and plug in wires, to change amps, and cabs, but it forces me to pay attention.
I have not blown an output transformer since labeling the wires. Years ago, I blew the output transformer of an Epiphone Valve Junior with an impedance mismatch. Thank goodness I learned that lesson on that cheap POS amp.
