Pros: Great DAC, Headphone Amp & Preamp for the money
Cons: wish there was a switch to enable output from headphones and speakers at the same time if/when desired
I just got an HDP (my first DAC/headphone amp!) a few weeks ago and have been enjoying it immensely since I got it. So far, I'm just using it as a USB DAC and headphone amp plugged into one of my W7 laptop's USB ports and playing mostly lossless files with Foobar with the WASAPI plug in with Foobar's volume at zero db (max) going out to the HDP. I've been pretty much blown away by the upgrade in sound the HDP provides over the stock sound of my HP laptop which I had previously thought was pretty decent with my 530 IEMs. But now after experiencing the difference the HDP has made, 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 3 in 1 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 am amazed, indeed at times almost shocked by how much better my 530's sound plugged into the HDP. Lossless files really sound so much better with this setup so I have already started to rebuild my music library with more lossless material.
After seeing some of the comments about the HDP in another review thread about hiss and various volume pot issues experienced by some, 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 I would think should certainly reveal it if any is there. But 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) which is pretty close to max volume. 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 which is barely turned up at all.
In sum, neither hiss nor channel imbalance is a problem for me at all with the HDP, even with my IEMs. 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 likely be able to hear more hiss with my unit than I do.
Another thing I should mention is that I initially found I was getting some occasional annoying glitches in the sound that were apparently being generated by my computer through the USB connection. This led me to try the WASAPI plug in for Foobar which bypasses and isolates the data stream from the WIndows volume mixer, enabling bitperfect output from the computer to the HDP. Fortunately, this simple fix completely eliminated those annoying audio glitches.
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, small, easily transportable package that should be able to scale up nicely as I expand my system with active speakers and full size headphones (probably HD650s) in the near future.