Is It Safe To Connect Speakers To Two Amps??

One other possibility might be to shut your tube amp down (its own power switch) while the music is still playing. I don't know if this this would be safe for your tube amp. If not, let the tube amp at least cool down enough so the tubes can't amplify anymore (few minutes?). Then switch it over with a good switch that doesn't use resistors while playing. This might be one to ask your amp company to see if it's safe to do. Others please chime in, if this is not a good idea. I'm not sure.

Then switch it over with a good switch that doesn't use resistors while playing.

Let me clarify. I don't mean change the switch over with music playing, just no unneeded resistors a switch might put in the signal path. Definitely the amps should be off to change over. Sorry.

Hifihvn raises an important point about tube amps. They should indeed never be operated without a speaker load, or a reasonably equivalent high power resistor as a load. I too have my doubts that 150 ohms is low enough to be suitable in all cases. And a substantially lower value would, with most amps, mean that the power rating of the resistor would have to increase significantly.

The reason a load is needed is that with no load, abrupt changes in the amount of current that is fed into the primary of the output transformer can produce extremely large voltage spikes, due to a phenomenon called "inductive kickback." The result can be a ruined transformer or output tubes.

The concern is most significant if music is playing through the amp. However, I would not rule out the possibility that even with no signal present, turn-on or turn-off transients might cause a similar effect, perhaps cumulatively over time if not immediately.

Regards,
-- Al

The tube amp would not be on if the other amp is on. The switch can be set for the speakers to go to the tube amp when it is turned on and when turned off to switch to the other amp. There is a delay to allow the amps to shut down completely.

Almarg, thanks for clarifying.