Two amps into one pair of speakers

This is a newb question, but my friend has two integrated amps hooked up to his speakers, one McIntosh and a Prima Luna. One is connected with banana plugs and the other with spades. He said this will cause no problems as long as they are not both sending signal at the same time. Is this true. It just seems a little strange to me.



Just to clarify what one poster stated: you CAN run signal from one pre amp into two amps (via simple Y splitter), or?

Before I got my custom switch built by an EE friend (it's setup to protect a tube amplifier at all times), I used 10AWG Blue Jeans speaker cables with the welded banana plugs and just swapped cables back and forth with my home theater receiver.  I'm still using the switch and it's the barrier to upgrading speaker cables as there's more cables required and a clear sub optimization in the setup.

There are inexpensive speaker/amp switch boxes available on Amazon. I got Bryan from to build me a custom switch box which allows me to route two amps to single set of speakers and a sub. Added benefit, it has 4-pin balanced xlr taps for running hard to drive headphones. 

BAD idea!!   The output impedance of a power amp is a fraction of an ohm, so do you really want to connect both of your amps to nearly a dead short?  Depending on the amp design, when a modern amp is turned off, it likely has a protection relay that disconnects the speakers from the amp output.   BUT if you have an older amp, or maybe an inexpensive amp without a relay, then the output transistors are connected whether it is on or off.  It really depends on the design.  

And mistakes happen... what if you accidentally turn both amps on?  

Simply a bad, bad idea!!  

Smoking in bed.

Why is this thread even on Agon, the 2nd amp for a gaming system?