2 amplifiers connected to 1 set of speakers


I’ve been in the hobby for a few years and my wife asked me a question that stumped me.

Can you have 2 amplifiers, connected via their own individual sets of speaker cables, connected to the same pair of speakers at the same time? I told her I didn’t think that would be advisable.

The question came about when she saw me disconnecting cables from my solid state amp and connecting the cables from my tube amp. (both were off of course). She asked me why it wouldn’t be ok and I started babbling that the signal from one amp would then travel through the other set of connected cables into the amp that was not in use. Even if the other amp was off that could be problematic. If the other amp happened to be on then it could prove catastrophic for both amps and potentially cause an electrical fire.

What is the correct answer fellow audiogon members? Ralph?
ghasley

Showing 1 response by kingsleuy

DON'T DO IT!
I've done this.  A long time ago.  Twice.  With two receivers.  First, by accident.  Second, purposely.  
There are conditions that may allow you to do so with no harm.  As long as both are NOT ON at the same time.  But without diving into the circuitry with a schematic, one will not know.

The details are clouded but here's the best I can remember.
The first thing I notice is the system will not play as loud.  One usually knows how loud their system plays at say the 9:00 position. (btw this was enough to kill the other amplifier)  But going on.  So, you turn up the volume to 1-2:00 position to achieve the correct volume. Why?  I figured that I was feeding power to my speakers as well as backwards into the other connected amplifier.  Which it's output devices did not like.

The first time noticing something was not right (the 9:00 position), I just wiped out the 4 output transistors of the Connected Receiver.
The second time I went for the 1-2:00 push.  And then turned the Connected receiver ON.  OH  BOY.  A loud burp from the speakers.  Flashes.  Smoke.  It blew just about all the fuses and the outputs transistors of both receivers.  Plus the driver circuit board to the output transistors of the Connected receiver.  Quite exciting.  And destructive. 

DON"T DO IT.