Thanks for providing schematics and links Deon , very interesting . Do you make your own board or order from ESP ?
I've just received this DAC :
Replacing stock JRC5532DD with OPA1612 makes huge , and immediately noticeable difference for the better , night and day .
Other opamps I tried in the DAC ( 6.4VDC measured directly on pins ) :
OPA2134 : Sweet , warm sounding - can live with this one .
OPA2888 : Doesn't work , too much gain - distorts
OPA2111 : OK
LME49720 : Not particularly good in this application
2x LM49990 : OK , but OPA1612 still notably better
LM6172 : 2nd to OPA1612 , better than all others
OPA2137 : Distorts in this application