Connecting multiple MP3 players to one amplifier...

Hi everyone! I'm new to the forum and I really like the communication that goes on here. I'm a real novice when it comes to audio but I have played with many setups over the years just enough to be dangerous ;)

I've got a special project where I am attempting to run 6 portable MP3 players into one amp (don't ask) which came out of a set of old PC speakers. Each of the MP3 players are being turned on or off individually and my first thought was that I could daisy chain all of the audio jacks (1/8 inch stereo) together and it might work. Well, the first thing I found out was that the MP3 players are also getting power through the audio jack and therefore I could not turn the power off like I thought. I still don't understand this but believe me it's so.

I then tried to isolate the audio cables, all three conductors, usign signal diodes but that caused another problem. For some reason the players would go into a mode where they could not be turned back on once the power was cut.

Anyway, is there any easy way to isolate the 6 outputs other than possibly using relays to completly isolated each signal line? I could do this since I am using 12vdc from a PLC to control the on/of function of the player itself.

Any suggestions you may be able to provide on this topic would be greatly, and I mean greatly appreciated...

3 answers Last reply
More about connecting multiple players amplifier
  1. Use resistors, not diodes.
    Yes it's do-able.
  2. Yes, I'm going to try the resistor network to see how it works. I simply cannot understand how the MP3 players were getting there power from the audio output lines? I had power turned off to the players totally, i.e., a hard disconect, however when I tried to tie the 6 outputs together and feed them into the pre-amp, all of the units came on or were recieveing power which could have only come from the audio lines. Is this same thing going to happen when I use the resistor network?
  3. Just to let everyone know, the problem has been fixed using the resistor network and the problem it turns out that although you cannot get power through the audio jack, you do have ground which is common with the ground on the board. Since I was switching the power on and off externally,I had decided to switch the ground line instead of the power which means I had them hard wired to the power source, when the grounds were connected together on the audio jacks and tied them to the ground on the pre-amp, they all lit up when the pre-amp was turned on. Anyway, by switching the grounds and using the resistors, the unit works as designed...
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