Tklp, what tube amp are you using?
Niles themselves have concerns about keeping a load on the tube amp at all times, in this speaker switch(link below). They recommend an extra resistor on the tube amp at all times on some products. I don't know if the 150ohm,5 watt resistor would be safe for all amps. I would not try it, unless the company that built the amp says ok. The other switches do not even mention tube amps, and whether it would be safe. Maybe the manufacturer of your amp could recommend what to do. This PDF link is for a speaker switch, that expresses the load at all times. Pages 4-7. [http://www.nilesaudio.com/images/PDF/SS_manual.pdf]
Niles themselves have concerns about keeping a load on the tube amp at all times, in this speaker switch(link below). They recommend an extra resistor on the tube amp at all times on some products. I don't know if the 150ohm,5 watt resistor would be safe for all amps. I would not try it, unless the company that built the amp says ok. The other switches do not even mention tube amps, and whether it would be safe. Maybe the manufacturer of your amp could recommend what to do. This PDF link is for a speaker switch, that expresses the load at all times. Pages 4-7. [http://www.nilesaudio.com/images/PDF/SS_manual.pdf]