How do I tell which wire is which if I have a copper wire, red and green coded wire? Is the unshielded copper wire ground?
Red is for Right. Blue (or green) is for Left. Copper is for ground (I remember this with the mnemonic Red Right bLue Left Copper Common). All 3 are coated in a lacquer you need to burn or scrape off before you solder. With standard headphone plugs, with the plug facing away from you, the right pin is right, the center pin is ground, and the left pin is left.
- Common (or "ground")
- Insulating ring
I've replaced connectors on a lot of different headphones over the years. What I have found is that there is no standard for wire colors. They are all different.
Consumer headphones, professional headphones, intercom headsets: they are all different.
The proper way to check to see which wire does what function is to measure it.
Put the headphones on and do a continuity check between each of the wires. Listen for the "tick" that comes out as you touch each wire.
Common to left hot: tick comes from left speaker. Common to right hot: tick comes from right speaker. Left hot to right hot: tick comes from both speakers.
If you are using a multimeter on the low-ohms range, you will see that the left-hot to right-hot resistance is about double that from the common wire to either the left or right speakers.
Bottom line: don't rely on wire colors. Test it and ensure that you get it right the first time.
There is a general "R Code" for audio equipment. R: Red, Right, Ring, Recieve. When you have a TRS connector (Tip/Ring/Shield) the Ring always goes to the Right channel on a L/R system, the Receive on a Send/Receive system. The Left/Send/Tip doesn't have a standard. Black used to be the common color, now it's white, sometimes it's blue. It doesn't matter because you use the R as the identifier. The bare wire is the shield, though it doesn't provide much shielding or grounding, it's purpose is to create the flow loop for discarded electrons. But since few know anything about that part of the system it is referred to as shielding, grounding, common, but it's all irrelevant.