My ha-160 (not D, not DS, just amp without dac) has arived today. Immediately after plugging in HD 595 into the left socket I have noticed static buzzing of quite high intensity. It was less noticable with Q701 and least noticable with HD 650 but still there. (interestingly the right socket appeared to be silent) I have fixed it by connecting my dac to pc with optical / toslink cable instead of usb (luckily my onboard had an optical out)
After that the the amp is basically dead silent with Q701 (no matter of the volume), while slight hiss becomes audible with HD 595 when I turn volume at about half intensity (this however makes the 595s so loud I would never use settings this high) So for any practical conditions the hiss is gone. But still left me puzzled: shouldn't this problem be fixed already by Burson ?
Sorry to revive an old thread but I got the same amp (HA-160, no D or S), and experience exactly the same problem. My HD 598 plugged in to the lower impedance output (the second one, 15-150) has a lot more of this buzz than my HD 700. HD 700's buzz is still very much noticeable and distracting, however.
When connected to the first port (high impedance, 150-600), the noise is outright unbearable for HD 598 (50 ohm) and just intolerable on the HD 700 (150 ohm).
The buzz is present whether or not anything is connected to the amp and the noise level is constant throughout the entire volume range. This tells me an external factor may be playing a role here. I'm going to debug it by isolating potential causes one by one. I'm going to start with distancing the app from other electronic equipment like my TV, receiver, laptop, external hard drives, etc. Then, I'll try different power sources. Right now, it's plugged in to a (not cheap) surge protector.
If none of those work, I'll point fingers at Burson because as high-end products go, I want absolute silence when silence is all there is to be rendered.