That's right. Sony manual says 5th rung is non connect, but unclear whether they are talking about the headphone plug or the internal wiring of the jack. However, seeing as how Sony co-authored the spec, it would be strange that they don't have the full spec implemented on their DAPs. It would be very simple to wire the 5th rung to the common GND. Looking at the PCB image below, you can clearly see the 4 wires but there is also one more red wire that appears to be soldered to the 5th rung. I emailed the adapter maker on eBay so will share once I hear back.
I just did a quick continuity check on my WM1Z. On the 3.5 mm TRS plug, the S is the common grd, and there is continuity from the S lead to the chassis, as measured on the edge of the gold ring around the 3.5 mm TRS plug. The 4.4 mm plug 5th ring grd is actually the case grd on the plug. There is no continuity to the same point that I measured the 3.5 mm TRS plug S lead to. So it does not look like the 4.4 mm 5th ring is connected to chassis GRD. If a 4.4 mm 5th ring Grd is all that is needed, then a workaround would be to wire a 4.4 mm 5th ring to the S connector on a 3.5 TRS plug. Plug the 3.5 plug in along with the 4.4mm, and the 5th ring will have a Grd, the same grd as the 3.5 mm S lead uses. This is assuming that all the 4.4 plug needs is a common chassis grd. on the 5th ring. No idea if that will work, but easy enough for somebody with the right setup to try out.
Read the above discussion. It might be safe if the 5th point on the 4.4 is wired to ground inside the WM and then wired to the common ground on the 3.5
The workaround I suggested would be connecting the 5th ring from a 4.4mm plug with one end of a wire, and the other end of the wire to the S lead of a 3.5mm plug. That way, you can use the 3.5mm plug, plugged in and connected to chassis grd, and the grd is then bridged to the 4.4mm S 5th ring via the wire. So you have tapped onto chassis grd from the TRS socket to TRS plug S grd, wired to the 4.4mm S lead. This is not as good as wiring the 4.4mm S internally to chassis grd, but it is an electrical equivalent, with the advantage of not having to open up the WM1x and does not involve any soldering on the 4.4mm socket, or chassis, and also no need to open the back of the WM1x. If this works, then the internal grd can be added at a later date, as a more direct grd. And if it does not work, then it was 100% non-intrusive to the WM1x, and you can just cut the S lead off and salvage the plugs for other uses.
Indeed. However I don’t see why anybody would want to go to all this trouble just to get a single ended signal, why not just use the 3.5 to get that.
As mentioned earlier in the thread, many times those plugs are advertised as doing one thing but the included diagram shows they do another.
Well they can't have changed the physics of the power so the balanced must still have more unless they have limited the volume on balanced
