Update on the Sundara jack replacement with the PJ-327A gold-plated SMD jack. ALMOST A DISASTER! not quite, just clickbait. Well, the jack was about 0.1mm too wide and almost did not fit in the CNC carved hole where it's supposed to sit, but with some elbow grease and some finicking, I managed to push it in with the back of my precision screwdriver. Steps below with images:
1. Disassemble the Sundaras. I will not go into detail since there are countless examples in YouTube on how to reach the insides. But what I will tell you is to use much care specially with the screws. Mine had a crossthreaded screws and apparently were all magnetic. If I had dropped one, I might have punctured the driver and the mesh too!
2. Once you have the driver outside the housing, carefully lift off the jack + PCB combo as it is not glued or pressfit at all (at least mine).
3. Cover the driver with something, but do cover it please! Also, use the screwdriver to hold the cables in place.
4. Desolder the jack. How you ask? The method I used is simple. Heat one pad and make some upward pressure. Move to the other pad, repeat. Move to the other pad, repeat... and eventually the jack comes off. After 3 or 4 cycles, the jack came loose. Here is the PCB for reference. Note how the "L" silkscreen label above the cable is connected to the pad to the left of it (or right depending on your perspective). The "G" pad is connected to the furthest pad (or not), I did not measure it and I don't plan on explaining the Pythagorean theorem to you.
5. The third step is to... wait this is the 5th step... I lost track since I am doing this mod very late after a long day of work. Anyways. Ignore this step.
6. The Pajama jack (PJ, get it?) will not match the two NPTH holes in the PCB. Easy fix, remove the frontmost peg with a pair of pliers or just using some sideways pressure since the plastic is very rigid. Image below shows the peg removed.
7. Since one peg is gone and also the pads on the PJ jack has a 20% matching ratio with the pads on the PCB, we will need to glue together the PCB with the jack, or vice versa. I used some old E6000 I had lying around which has a slow cure in air (no UV). I know, it's crap, but who cares.
8. Position the jack as straight as possible so it will have a higher chance of fitting the cup. Then solder one pad followed by the other. I used some Mundorf Supreme solder with some Chipquick no-clean SMD flux. The "L" cable will have to be soldered to the OPPOSITE SIDE of the connector, close to the "G" cable. This is because the PJ connector has a mechanical switch, and we are not interested in soldering the cable to the switch but the tip contact which happens to be on the opposite side. Do not be tempted to solder the cable on the exposed metal on the topside of the jack since the jack will not fit the cup.
9. Now, with care, jam the jack in the driver! Yes, you will need to apply some force but it will fit. Just make sure to insert the jack as straight as possible. I also found it easier if the jack is slid in and not inserted from the top. YMMV
Note: the mesh on the back does not seem to be metallic. I have tested it myself with a multimeter since I was worried I could short the pins.
10. (Optional) Test the continuity of the connector. You will have to touch the cable to the top left on one probe and with the other probe, insert it inside the jack since the other cable is inaccessible. You should get a reading around 32 ohms nominal.
11. Reassemble the Hifiman Sundaras. Take care with the screws. If they seem too hard to screw than they were to unscrew, you might be crossthreading them. Unscrew all the way out and try again. Screw in all the screws until you are satisifed, but if your Sundaras are like mine, I'd be too scared to put too much pressure.
12. FINAL RESULT: (pardon my oh-so-cheap Openheart cable, it looks exactly like that in person). The jack is stiffer than a grandma's walking stick, plus the sound quality is superb compared to the old tin-plated 0.01$ jacks Chifiman decided to use on a mid-fi headphone. The plug also does not have any leeway like before.
I hope this post cheered you up and has been useful to ya'll.