NuForce Icon HDP (High-end Headphone Amp, USB DAC, Preamp)

I purchased the Nuforce Icon HDP along with Sennheiser HD 650 headphones as my first desktop setup about six months ago. I'll start off by saying that the HDP has been a fantastic purchase that I am thrilled with and enthusiastically recommend, especially as a starter desktop setup.

The HDP has loads of power and easily drives my Sennheiser HD 650s and other high impedence headphones such as AKG 701 with lots of headroom to spare. This is an awesome attribute for a unit at this price point as it will have ample power for almost any headphone on the market, regardless of price. With my Sennheiser HD 650, I usually listen from 11 am to 1 pm on the dial and never go past 2 pm. It absolutely drives them authority and tons of power to spare.

The HDP offers a sound signature that is very clear, transparent, detailed, fast, neutral, and with a nice sense of overall polish and refinement to the sound. My previous Dac/amp prior to HDP was the very popular portable Ibasso D10. The HDP was a very significant improvement over the D10 in all areas. The HDP seems to pair especially well with headphones that are bass heavy and not bright, such as the Sennheiser HD series and Denon AHD series. It specifically does a great job of really tightening up the bass on these headphones, which can be a little boomy or loose on many other amps. With the Sennheiser HDs especially, it also helps give them that extra detail and speed they can oftentimes be missing. The HDP is also a really nice combo for the AKG 701/702 as it really gives them extra bass weight. 

One area that was a huge bonus for the HDP compared to other popular units in its price range is the fact that is has an outstanding USB section that supports full 24/96 high resolution music files. I regularly download high resolution albums from HDTracks and play them over my laptop via USB and they are very noticeably better than standard 16/44 regular cds. I have tried comparing the HDPs USB section with its coaxial and optical inputs on numerous occasions and have never been able to discern any differences, which is high praise for the quality of its USB section.

Since having purchased my HDP, I have attended several local meets and have auditioned gear much more expensive than it such as Woo Audio WA6, Beta 22, Bijou, Eddie Current ZDT, Supra, etc. While the really high-end gear does exceed the HDP--most noticeably with larger soundstage--the price to performance ratio of the HDP compared to any of these more expensive units is just phenominal. No matter how high-end of gear I audition, I am never disappointed going back to my HDP. My HDP has helped me to content with my gear and focus on my music collection. While I will likely upgrade to higher end gear over time, I am truly enjoying my HDP in the meantime and am in no rush to upgrade any time soon.

I owned the Nuforce HDP for two months, I tried it with several headphones ranging from the 600 Ohms DT880 to the 300 Ohms Senn HD600 and HD650 and 62 Ohms AKG K702. Actually I wasn't impressed that much. I didn't feel that the amp had enough juice to drive any of the headphones mentioned above, and the DAC had too much emphasis on treble which seemed too exaggerated and unnatural to my ears. When listening to several audio tracks and in comparison to Headroom's Ultra Micro DAC I heard distortions in the upper highs that never showed in the Ultra Micro. The imaging and accuracy of the UM DAC was far beyond the reach of the HDP, but on the other side, the HDP performed better than my Marantz CD5004 regarding clarity and detail. The best sound I got from the HDP was from the Marantz CD player connected by coaxial/ optical connection. But USB connection sound quality was thin, harsh and lean. 

The volume knob is made of cheap plastic and sometimes I heard static when moving the knob between 1 o'clock and 3 o'clock. On the other side, the HDP is very small size, very portable and it has many connections on the back which makes a great versatile unit for many purposes.

So all in all it is not a giant killer. It doesn't function as good as DACs or Amps double or triple the price, but you get what you pay for. A $200 DAC and a $200 Amp no more, no less.

This is my first headphone amp. It drives a set of Sony MDR-V700 s. Definitely allows my headphones to exploit the dynamic range of classical music. Easy to discern bit rates that used to hide in my speakers and headphones before.

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.