Well, I finally got my hands on amp 2, which is the Pro-Ject Headbox SEII with the revised circuit board, and it sounds completely different from the original model. A lot more bass, punchier, quiter, and more pleasant. Also it is a capable of producing more clean volume on my HD600s.
Also build quality seems much better.
So amp two turned out to be a much better amp.
Also build quality seems much better.
So amp two turned out to be a much better amp.