Two amps to one speaker


I use an Ayre VX-5 Twenty to drive a pair of KEF LS50s.  Occasionally I'd like to use a pair of Cary 572 SE monoblocks.  Would I create a problem by connecting cables from the Ayre with spades and those from the Cary with bananas?  Of course, only the Ayre or Cary monoblocks would be powered up at a time.

The cables from the Ayre to the KEFs is Cardas Clear Day with spades at both ends.  I suppose I could have one end converted to bananas, and that might be the proper solution.

db
dbphd
DB, no, absolutely don’t do that. In almost all circumstances the outputs of two power amplifiers should not be connected together. You would likely damage both amps, eventually if not sooner.

When you are using the Ayre the secondary (output) winding of the Cary’s output transformer would have considerably larger voltages applied to it than when it is operated normally. And it would step up those voltages to much higher voltages than are normal on its primary side, and apply those much higher than normal voltages to the output tubes and related circuitry.

And when you are using the Cary, the Ayre could very conceivably also be damaged, as a result of the "reverse breakdown voltage" ratings of its unpowered output transistors being exceeded. (And of course having the Ayre powered up while the Cary is being used would cause other major problems).

This question has been discussed in a number of past threads, and you can find some suggestions in them of various speaker-level switching devices that are available. If you want to consider one of those, though, be sure it is rated to be suitable for use with amplifiers as powerful as the Ayre. And keep in mind that in most cases a tube amp having an output transformer should not be in a powered up state without a load being connected, especially if it is being provided with an input signal, and in many cases these switching devices may not apply a load to the unselected amplifier.

Regards,
-- Al

Here's a very recent thread with some suggestions

https://forum.audiogon.com/discussions/a-rookie-question-re-two-amps-one-pair-of-speakers
Thanks for the responses.  Al, I was pretty sure I knew the answer was don't do it, but I couldn't give an explanation as you did -- now I understand why I shouldn't do it.

Except for Oppos, I buy almost all my equipment used, and that's true of the Clear Day speaker cables. They're a bit longer than I want, so I think I'll have them cut into four pieces, each with spade-to-amp and banana-to-speaker termination.

BTW:  Ayre C-5xeMP, K-5xeMP, VX-5 Twenty to KEF LS50s delivers fine sound.  I supplement the LS50s with a pair of Velodyne HGS-10s, low passed with a 100-Hz card by a Beverage RM-3.
Sounds like a very bad idea good luck though!!
Here’s a very recent thread with some suggestions

https://forum.audiogon.com/discussions/a-rookie-question-re-two- amps-one-pair-of-speakers
The above link was only good for switching between two solid-state amplifier, to switch between a tube amplifier and solid-state amplifier, there was a thread discussed two years ago:

https://forum.audiogon.com/discussions/speaker-switch-that-protects-tube-amplifier
I've decided that each amp will have its own speaker lead, terminated at the speaker end with a banana plug.  When a particular amp is in use it will first be connected to a speaker and only then powered up.  So at no time will two amps be connected to any speaker, nor will any amp be powered up without first being connected to a speaker.  I certainly don't want to put the Ayre VX-5 Twenty nor the Cary 572 SE monoblocks at risk. 

db