I am heading in the same direction with my DS DAC. Have you played with power cords on the external power supply vs the DAC itself?
Modifying PS Audio DirectStream DAC
I just finished my first mod. It was for my PS Audio DirectStream DAC:
- Swapped in two Edcor XS4400 transformers.
- Switched the power supply for the analogue board to a Farad Super 3
- Added 3M AB6005S EMI/RF shielding to the inside of the case and on the larger chips
It sounds amazing now. Its like having a new piece of equipment. I was A/Bing it with my turntable and got confused as to which was playing! All the changes were pretty straight forward. They are described in detail on the PS Audio website. There are lots of pictures to help.