Adding a line in to my Sony portable

My Sony ZS-X3CP portable stereo has no line in input, it has a CD player (able to play MP3) and tuner only.
My intention was to do away with the cd player and just add a linein somehow instead so i can plug my tiny Sandisk MP3 player instead. Any idea how i go about this. I took it apart and can see a large ribbon cable from the CD player feeding what looks like a switch board. Where do i start! I recognise some components and can solder but no idea how i would make my own pre amp circuit or where the existing one is. I can supply pics if needed.

thanks

Ken

How many wires in the ribbon cable? If that's the only connection to the CD drive, then two of those wires carry the left and right audio channels.

You can locate them if you're careful how you touch things. You need to find a good place to solder wires in or near the ribbon cable. Then you run L & R audio to your line-in jack. Along with a ground cable.

It's easy if you have a bunch of small jumper cables with alligator clips. Put pins or needles in the clips and you can touch wires in close quarters. Also to pierce insulation when needed.

The first thing you need to do is to use a meter to locate any supply wires in the ribbon cable. Check all combinations of two wires. What if you detect a positive DC voltage? Make a mental note to avoid touching it afterward.

You want to use a ground reference for your line-in. Usually it's the ribbon cable wire which shows zero resistance to metal frames inside the unit. Usually.

Then you poke around the other ribbon cable wires listening for an audio signal. You can listen through headphones without amplification. But again it's safer if you patch into an auxiliary sound system.

Before hooking up headphones, put a small value capacitor inline just to be safe. Do without the capacitor only if you're sure there's no DC at any wires you're tapping into.

An oscilloscope is invaluable of course.

If you can find three ribbon cable wires that give you L channel in one headphone and R channel in the other, with no DC component, then that is most likely the correct arrangement for installing your line-in jack.

Preferably you should disconnect the CD drive audio so as to reduce complications. No guarantee that you can get away with leaving it connected.

If you're lucky you'll have matching volume levels, zero DC components, etc., between your Sandisk and the Sony.