Crack open the little box. This is easily done with a small knife. Pry a potato peeling knife in the crack at the very end. Wiggle it a bit. You may hear a bit of cracking, the housing consists of two halves that are only lightly glued together. Repeating the procedure in all 4 corners will work.
There's a black plastic inner box. Use the same knife to pry that open.
Severed the trace \ \. This is pin 2 of the Micronas chip controlling pin 11 of the T-amp chip. Pin 11 of the T-amp needs to be grounded, but on the side of the T-amp only a very thin trace is available, or the pin of the chip itself. Easier is to use the small soldering island on the Micronas side, as shown. I put a tiny blob of solder there first, and some solder on the copper wire, so the only thing left was to just melt the blob and thus affix the wire. Just scratch away some paint to get at the copper of the ground area (left arrow).
Now the T-amp side: Removed the capacitor where the long arrow points, just gently heating it loosens it. Then connected the soldering island to ground, the rightmost arrow points. Just scratch away some of the paint of the ground area to get at the copper for soldering.
I was informed by Frank Vachell Philpot that above did not work for his amplifier. Indeed I now encountered an amp where above procedure did not work. Possibly there are different versions of the board. My alternative is to connect the soldering pad to the lowest (GND) track on the board, as shown below (sorry for the fuzzy picture):
Assembly is the reversal.
When I connected the speakers back to my Mac mini (or, more precisely: the powered HUB that drives my (old) Cinema display) the device was detected and the alert popped up that you normally get when you switch off sound with the keyboard sound key. Then it disappeared. And popped up again. And disappeared. Etc. That stopped when I upped/downed the volume with the keyboard keys. It's worked fine since.
Only disadvantage is that your computer can now not power down the amp any more. So, your energy consumption is up by a few watts, even if you're not listening to music. Sorry about that.