Audio Technician Help?

This question is for a GOOD audio electronics technician. I have been told it is not good to connect the stereo line level outputs of an MP3 CD player together in order to feed a mono PA amplifier, because it overheats the audio output stages of the player. Is this significant? Do I need to insert series resistors before I tie the two channels together or should I just put in a Y adapter and be done with it?

It depends on the particular player. Lets say the line output impedance is 600 ohms. When you tie the two channels together the impedance will drop to 300 ohms. This means twice the current will flow from the solid state device which feeds the line output. If the player is built to tolerate the increased current flow, there would be no problem in connecting the two outputs together. However, if the player is a cheap toy, that might be another story.

If you could see a schematic of the player, you might look and see if there are series resistors in the feed to the line output jacks. If there is, there would be no problem connecting the two channels together, because the series resistors would isolate the channels sufficiently.

My gut feeling is that almost all players would tolerate connecting the line outputs together. If connecting the two channels together would harm the player, that means just shorting the outputs to ground would also harm it. It would be a sorry-cheap piece of junk if just shorting the line output to ground would burn it out. line output is when the signal is routed after the pre-amplifier and before the amplifier of the player. the are outputs, not inputs. the cd player has the same load either way.

by the time the electric signal has reached the line output the pre-amp of the cd player has already done its work. it won't hurt anything. however an adapter is cheaper than splicing a nice cable, doesn't have potential for short, and looks better. spend the $2.50.

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