I just got an HDP (my first DAC/headphone amp!) about 3 or 4 days ago and have been either listening (or just leaving it burning in) almost constantly since I got it. I'm using it as a USB DAC and headphone amp plugged into my W7 laptop running Foobar/wasapi at zero db to the HDP. I've really been enjoying the upgrade in sound the HDP provides over the stock sound of my HP laptop which I had previously thought was pretty good with my 530's. But now after experiencing the difference the HDP makes, I know better.
Compared to many here, I don't have a lot of money that I can spend on lots of audio equipment so the HDP's value proposition is very important for me. Although I don't have anything besides my previous stock setup to compare it to, the increased fidelity, clarity, space, transparency, etc. it provides has been dramatic and a wonderful revelation for me, especially with lossless source material. I didn't know my 530's could sound so good. I have already started to rebuild my music library with more lossless material.
After seeing some of the comments in this thread about hiss and various volume pot issues, I feel really lucky because the pot on my unit is as close to flawless as I could reasonably expect. I have zero detectable channel imbalance even at very soft volumes and I cannot discern any hiss at any volume I can reasonably tolerate with music playing through my Shure 530 IEM's which should certainly reveal it if any is there. I can only hear some very faint, barely detectable hiss if I listen hard for it with the volume turned all the way to max while no music is playing. Also when no music is playing, I can hear some faint crackling as I rotate the pot, but it only starts to occur when the pot has been turned past the 3:00 level (with HDP in vertical orientation). But this is a complete non issue because the maximum volume I can comfortably listen to the HDP with the 530's is at about 9 to 9:30 with most material.
In sum, hiss is absolutely not a problem for me at all with the HDP. However, I'm 58 and my ability to hear high frequencies is most certainly diminished, probably a bit more than normal for my age. So someone with more sensitive hearing would probably hear more hiss with my unit than I do.
The only disappointment I've experienced so far is that I don't find that the HDP sounds as good as the somewhat processed sound my stock sound card/driver puts out for ripped HD movies and I'm not sure why that would be. Perhaps I haven't got my media player (Daum Pot Player) configured optimally for watching movies through the HDP. . . ? This is something I need to investigate further. But for music, the HDP is simply awesome compared to what I was used to listening to before.
Another thing I should mention is that I initially found I was getting some occasional annoying glitches in the sound that were obviously being generated by my computer through the USB connection. Fortunately, these glitches appear to have been completely eliminated since I switched to using the HDP with Foobar with wasapi. That appears to be a very significant advantage to using wasapi on my system. And so far I'm finding it convenient to leave the default sound set to my computer's sound card, but keep Foobar set to use the HDP.
To sum up, although it was a significant chunk of change for me, I'm really glad I decided to spend the money on the HDP as it's providing me with a huge upgrade in sound for music in a nice looking and small easily transportable package.
Edit: Well, I've played with the audio settings in my video player and I'm pleased to find that after making some adjustments the HDP sounds much better for movies than I initially reported and is now providing an upgraded experience similar to what it does for music.
