jaudio said:Check all ground connections(including signal input ground).
Check the connections from the drv134 to opa549. If the drv134 is not well connected,you will get hiss
What is your gain? It might be too high.
OPA549 has the max voltage list at +/-30,your supply voltage might be too high.
Nobody noticed yet that there's something missing on this board?
No PSU caps on the OPA549 chips?