Please bear with me here ...
I have a Digital Audio Player that I'd like to use as a source into my DAC for a little desktop headphone amp system. The player has a 3.5mm output that is switchable from a line-out to a digital coaxial output. The original cable that came with the player is just a short adapter with a 3.5mm TRRS plug to a female RCA. They (Fiio) used to have a 3.5mm to RCA cable available but that is discontinued and so are the replacement adapters. My adapter is on the way out. So my question involves building a replacement cable.
I know how the adapter is wired. The 3.5mm TRRS plug only uses the contacts for the sleeve and the bottom ring. The upper ring and tip do nothing. BUT ... on the original adapter, the sleeve of the 3.5mm TRRS plug is wired to the center of the RCA female, and the lower ring of the TRRS plug is wired to the shield of the RCA female. Basically "backwards" if you will.
Using some mini 75 ohm coax and a small 3.5mm TRRS plug and following the wiring of the original adapter, I would have to wire the coax braid to the lower ring of the TRRS and the center conductor to the sleeve in order the copy the wiring of the original adapter. That will be very difficult to accomplish with this small, 3.5mm TRRS connector.
So, as a test, I wired a coaxial cable up in a conventional manner with the braid to the sleeve of the TRRS and the RCA plugs and the center conductor to the lower ring of the TRRS and the center pin of the RCA plug. To my surprise, this worked when connecting the player to the DAC. However, it is wired "backwards" from the original cable.
Aside from my being familiar with the cliche regarding digital either working or not working ... I know next to nothing about how digital audio works so I would appreciate it if someone who does know something about it can tell me whether my "backwards" wiring scheme is OK or not. If this were an analog audio signal, I think reversed polarity would be the main "issue" but again, as little as I know about analog tech, I know even less about digital. It's "working" but what are the downsides with my "backwards" wiring?
Thanks
