back of my sound system and you might notice it is an Altec Lansing for those MP3 players like ipod or some sort of similar version since it has that funky connector for the slot on the bottom of those units. I did notice it was pretty easy to determine what to solder to if I would have wanted to (or had to as I did not since there is an AUX input for sound on this model.) All you have to do is touch the ports inside (it is all DC so no chance of serious electrocution) on the points the stuff coming from the MP3 players port run into the main board and listen for the hum that comes from touching say the RCA's that are going into a live port on your stereo. if you get the hum then you are in business (also helps to look at the wires as they still are color coded red white black right left ground (black is ground for both right and left for those that do not know.) I was lucky on this as it was given to me by some one who has no computer knowledge let alone even knows what an MP3 is and would not want to know.(probably a gift from some one they did not want to offend) and I don't own nor will I be owning an MP3 player in the near future that will be hooked up to anything resembling a base unit. I mean I have computers and laptops for that right? if I get one it will be hooked up to my pirate radio station heh heh (relax it is under the 1 watt min that the FCC requires so totally legal.) so anyway the real reason for luck is it is, small, really good quality sound, AND has a nice IR remote.