OPA2134PA or 2132PA   They don't need any fine tuning or biasing really so can be easily swapped out without problem.

The second homemade board is the trickle charger using an LM317 regulator to provide a constant current to charge the NiMh battery.   The TLE2426 is on the main purple board which provides a two rail supply both of which have WIMA bypass caps (you can't see it in any of them pictures but...

Quote: Around 6-7 hours max. 

Yup.

Circuit based around CMOY design Custom PCB WIMA MKP10 input caps OPA2134PA op-amp Panasonic FM 470uF power cap Laser cut black acrylic for end plates              

^Ditto   One of them batterys would last you a couple of hours in a CMOY   It's also alkaline so within less than a week you have a dead battery on your hands £1.50 down the drain - cannot be recharged.   9V alkaline (or 18v x2) 9V Nihm (or 18v x2) Or up to 7.2V Li-ion/pol  ...

Two PCB's?   The wording for some of the protection PCB's for these batteries can be very misleading   example...

Have you tested charging the batteries with just that PCB alone?   Since it only seems to be a protection PCB not an actual battery management PCB

Any DC charger 12-13v @ 0.5-1.5A + 3 x 3.7v Li-ion Batteries (11.1v) + Correct charge protection PCB   = Good to go?   Or do you need a specialised charger as well?

The reason people are having trouble tinning the wire once they remove the enemal coating from it is because if you use a lighter to burn it off its leaves the wires surfaces pretty crappy and contaminated   It needs to be cleaned afterwards simple as that   or a different method to...

What do you need and whats suits you?   Do you need a mic? Do you mind them bieng openback? (allowing sound to escape) - girlfriend sleep - so no. that's the beyer's checked off the list and any open backs Do you competativly game at a high level? (probaly not nobody on this forum does)...