1. There are diferential, isn't? They are referencing to each other.
2. On the cable there are two L+ and L- wires inside a shield. On the RCA side they are terminated L- to ground and L+ to center (as expected) and the shield is terminated on this side to ground. On this side only. On the other side shield is floating.
3. This is called a general engineering knowledge. Sounds right?
4. False, and I use this trick on unbalanced RCA connections, as already mentioned in my first post.
1: Correct there is no reference needed WHEN the signal is balanced. An additional screen can also be present.
BUT there is no screen here. ONLY L+ L- and R+ and R- on the output of the device as it is a balanced stereo 2.5mm TRRS connector for headphones so the ground/screen is not needed nor present.
You are talking about 3pin XLR to RCA converter, we are talking about TRRS 2.5mm stereo headphone to RCA
2: Incorrect... there is NO shield and it looks like the L- and R- are connected to the screen of the RCA. Again you are talking about XLR to RCA which does NOT apply here.
3: Correct and that's why there are only 4 wires, no shield as it is for connecting a 4 wire headphone... 4 wires, TRRS, 4 connections only, no ground
4: It is perfectly fine to use this trick, in fact a lot of balanced to RCA work this way... BUT in that case the screen is connected to common and thus one can use L+ and R+ (or L- and R-) single ended BUT referenced to ground.
You can NOT do this trick by NOT using a ground reference.
This is called a general engineering knowledge. Sounds right?