Just saw this. When I tried the CM I didn't remove the Riv and Civ from the Miro pcb. It still worked.A word of warning for those building the XEN CM IV and using DIP8 plug-ins, like Paddy and Ripster did.
You MUST remove Riv and Civ from the miro board, and you must solder (SMD) Riv and Civ on the XEN boards.
It is NOT plug and play swap for DIP8 opamps.
If you want to go back to opamps later, you need to reinstall Riv and Civ on the miro board.
For those who are going to try other output stages like Patricks current mirror, or valve output stages, or pedja rogic diamond buffer and so on.... I would strongly recommend that you socket the Riv at least. Civ is not quite as easy because it is surface mount and underneath the board, but maybe still with a little adapter it might be possible. That way you can remove/add them as you see fit.
Personally, I installed opamp sockets for the opamps, and then just use some dip pins to go into pins 2 and 3. You can make little adapter boards etc if you like for different kinds of resistors, melf, SMT, and so on. That will allow you to try other stages where the Riv and Civ (if used) are away from the DAC board.
very practicalI had the opa627 installed initially and find it sounding lack of spatial quality in complex music. sounded flat and two dimensional. Installed a single AD844, well was better but not good enough. Stacking 3 of them, and wow...... i think it is the way for me. Currently taking the output from the buffered output of the AD844. I will experiment with taking the non-buffered output and connect them to an external buffer next.