HaveMeterWillTravel
Senior Member
Yes, that is the standard in audio gear. I was pointing out that it _need not_ be from an engineering standpoint.DIN audio (5 pin) had voltage signals for playback (pin 3 and 5) and current for recording (1 and 4), 2 is common.
Biggest issue usually in audio is leakage currents trying to equalize between 2 devices via the shield (audio ground) adding a small (unwanted) voltage drop over the common wire which adds to the audio signal.
As the shield of the RCA is usually connected to common and mostly also to the chassis (which may or may not be connected to safety ground) it will be impossible to make that connection balanced (and thus have high CMRR). Cable then also would not have to be shielded but twisted or the 'common wire' should not be connected to the chassis and the only the chassis would be connected to shield (and thus have 2 signal wires, one to common).
In other applications there are two-conductor balanced/differential signals paths. 3 conductors are not inherently required.
That is what I was pointing out.