What happens when you plug two outputs together?

For people who don't have test equipment or know how to use it, your next best troubleshooting method is to do swapping of parts to find the guilty device. Have a known good signal line level source, a known good phono level source, a known good speaker, etc.

Divide and conquer...

Sometimes you might find a cheap line output source at a yard sale of something, or borrow one from a friend. It doesn't have to be high quality, it is just for test.

Thanks Tom and Al. I had the volume control at 0, powered up and turn up slowly. When hearing no sound, I turn it back down. No bang or smoke, so may be things are still OK.

I got no sound coming out of my speaker, was trying to figure out which component was bad. I should have just used a scope to look at the outputs along the chain...

I haven't seen enough audio component schematics to be able to provide a comprehensive answer, but I suspect that more often than not no damage would occur in the case of the line-level analog outputs your question refers to. (Connecting power amplifier outputs together would be a different story altogether, of course).

I would expect that the chances of damage would be greatest if both components have low output impedances, and if one or both of the components is or are attempting to output a high volume signal and continue to do so for a prolonged amount of time. (If neither component were attempting to output a signal there would be little or no difference between the nominally zero volts each component would be attempting to put out, and therefore little or no current would flow). Of course, if signals are being put out the user is likely to be listening, and he or she would presumably and hopefully notice something amiss sonically, and then turn off the system to investigate.

BTW, I see that this is your first post here, so welcome to Audiogon!

Regards,
-- Al

What happens when you plug two outputs together?

BANG!

=-}

No, seriously, it depends on the device. Some outputs have absolutely no output protection, some have protection for limited time (like 5 second overload, 30 seconds, etc.), and some have "infinite overload protection".

A device might be advertised as "infinite overload protection" and still be blown, however, because that protection was ONLY for accidentally shorting the output to ground, and not into another power source.

It's just not a good idea to do that... =-}

keep it away from children.