Ok, so
> Try the Ether unbalanced on each output.
Had to solder a custom pentacon to 6.3 converter first
Works same as balanced, but I'm still getting overcurrent waring right after -30db on unbalanced.
> has a intermittent short, or same inside the headphones
Yes, there was a short because I tried to Ether via pentacon and it's compatibility is bad, to say at least.
Fixed shorts - still getting warnings.
> Contact RME service or your local distributor for advice.
It would be easier for me to pinpoint and solder through the issue myself.
Local distributors and service is not that great - it's easier for me to fix existing or a buy new one completely (no guarantee that it wouldn't overheat/overload as the previous ADI-2).
> Heatgun doesn't work in this case, I can tell you.
That's why you'll need to preheat the board first to 120-170 deg c at least.
8-10+ layer boards can deform and can get micro-cracks without a preheating.
> When one OPA1688 broke here only HP output 1/2 didn't work.
> But that might depend on how exactly it breaks.
I'll need to check, but it might be something power-related.
> This chip is NOT replaceable with usual soldering tools, don't anybody try.
I suppose its a SON (DRG / WGON or similar) package...
SON packages are fit for one time job only because they're used in thermal sensitive applications.
It's possible to desolder SON's with an infrared heat station (weller WQB 4000 or similar), but there's still a small chance of damaging, and they can get somewhere between 7K-25K$ easily.
It's also possible to desolder SON's with an inductive soldering iron (OK International's METCAL MX-5200 and similar), which are about 1-1.5k$+ with all the tips.
Just clarifying what's considered "normal" for such chip package.
So, yeah, desolder... and solder a SON hotswap bed, a small fan and put a rad on top of it, just to be sure.
Will measure op amp voltage, temps and write back - should be something simple... and surely will share some photos.
This whole shenanigans really might be due to a bad ether cable, but I can't really get decent volume out of it even without shorts and on unbalanced.
Thank you guys, hopefully it won't blow up after some tinkering... or I'll just buy a decent amp to pair up instead.
Have a great time of the day.