Hello,
If it's at the line out then it is probably "upstream" from the headphone amp IC as you say. Not only are the coupling caps between the stages suspect, the power supply filtering capacitors for the line out IC may be bad.
If you are able to post the amplification stages after the DACs then that would be helpful in pointing out possible culprits.
I'm not familiar with the mods but to me if there are DACs being stacked I would think that there would be some additional requirements on the power supply to those ICs, thus a change at the DAC power supply filtering cap (increase of filtering) might be necessary. Maybe that increase is already part of the mod?
Paul
|