NO you cannot have two amps/receivers connected to the same speakers at the same time. Even if one is turned off. Serious damage can/will occur to the amp/receiver that is turned off., and possible damage to both if you were unlucky.
The power from the amp or receiver that is turned on goes back into the one turned off and those transistors in the second amp/receiver are NOT designed to handle that sort of current backing ito them!
You could use a switch box that is designed to allow ONLY one OR the other but not both to connect at one time.
The power from the amp or receiver that is turned on goes back into the one turned off and those transistors in the second amp/receiver are NOT designed to handle that sort of current backing ito them!
You could use a switch box that is designed to allow ONLY one OR the other but not both to connect at one time.