The PCB is finished and currently building one of them for test purposes.

It is 100mm wide, exactly the same as the mentioned PCB's.
Differences: The PCB in the link is a trafo+rectifier+standard regs (fixed voltage)
My PCB does NOT have the trafo on board but also has rectifier on board.
The regs are not fixed but the well known LM317/LM337 with standard 'noise reduction' components and thus somewhat lower noise than the standard 78xx/79xx regs.
You can set the output voltage (with resistors) between 12V and 19V (standard 17V) and can provide 1.5A (so 0.75A/channel for stereo)

There is also a DC protection (one for each channel, + 0.6V/-0.7V) + a start up delay + a power supply monitor.
If the positive or negative supply is not O.K. (too high or low) the relay falls off.
You can decide whether you need DC protection or want power supply monitoring or not.

This protection circuit can be connected to any HP amp circuit so is sort of universal.


IMO both amps you linked to are excellent and have their good points.
PCB design looks O.K.
They are quite standard amps and can provide power in low and high imp headphones.
There is no protection circuit present in the LME49600 amp.
The TPA6120 is a current feedback design and doesn't like capacitances connected directly to its output.
So its no low output Z amplifier possible (if you like it stable)
It needs a resistor in series with the output which raises the output R.
NO problem for the 600 Ohm HP you plan to use, it may be for certain other headphones.
The LME49600 is a bit better in that aspect.
The 2x gain may be a bit on the low side for the sextets but can easily be increased without too much penalties.

Can't comment on the DAC's.
The DACs are all I2S in so you may need USB to I2S converters as well to make them work.