The Nuforce Icon HDP incorporates a full-speed USB DAC and full-function S/PDIF D/A converter, plus a headphone-amplifier circuit and preamp output. Supporting digital USB, S/PDIF in coaxial and 3.5mm optical (3.5mm) modes, along with an analog line input, the HDP's flexibility has been designed to accommodate all manner of audio devices. Icon HDP is expected to compete with other DAC and preamp costing up to several times its price and serve as the heart of a high performance audio system.
Check out some customer reviews:
1) I bought one of the original 12 HDPs as soon as they became available. Since I got it I've been running it 24/7 & it keeps getting better. For 6 months I've been looking for a dac or dac/amp combo that sounded good enough to allow me to move my $1895 Benchmark DAC1 HDR (which was further modded with $995 worth of upgrades) off my PC back to my stereo system (for which it was purchased). ll dacs later I've finally got the unit I was looking for. In fact, I can already say that when using full-size headphones to listen to music off my computer, I actually prefer listening to the HDP over the Benchmark. I can also say that using the HDP as a dac only feeding my Doge headphone amp, that the HDP is ALMOST as good as my highly modded DAC1 HDR. Now that is comparing this $449 device with what is essentially a $2900 device (one that probably has received more positive professional reviews over the years than any other dac.
I've got a good collection of headphones including the AKG K702, Senn. HD650, Grado SR325is, Shure SHR840, & Ultrasone HFI700 & the HDP drives them all easily, even the K702s which are notoriously hard for amps to drive well enough to get the best sound out of them. Many of the 11 dacs & dac/amp combos I've tried in the last 6 months of searching cost 2-4 times what the HDP costs & IMHO, none of them sounded as as good to me as this little Nuforce DAC. That makes this dac an unbelievable value for the dollar.
2) I am impressed with this little Nuforce HDP both as a DAC and as a headphone amplifier; which is high praise from someone who owns a $15,000 headphone rig with Stax SR-007, Sennheiser HE60 and HD800 headphones, a Woo WES amp, Eddie Current ZDT amp, and PS Audio Perfectwave DAC.
The HDP seems to offer a lot of performance in a small package, and easily outperforms my original Nuforce Icon amp that I bought May 2008 for my computer desktop. And the beauty is that it is small enough that I can use the HDP's superior DAC to feed the original Icon when I want to listen to speakers (both amps are the same size). The feature list is quite full, including 24/96 bit rate USB and 3.5 mm 24/96 optical inputs, 24/192 coax input, RCA or 3.5 mm analog input, 1/4" headphone output, and variable output level RCA preamp out. Not many DACs in this price range offer 24 bit/96 Khz sampling rates, and even my 2x more costly Apogee mini-DAC only does 24/48 via USB.
The HDP using 24/96 USB input from my Macbook beats all my other $100 - $500 USB DAC/amps in the house, and even beats the headphone output of my Apogee mini-DAC with USB. The HDP's RCA line-out seems almost equivalent to the Apogee's 1/8" line-out as well, where the Apogee seems to be a little more refined sounding at times (if using my upgraded Sigma 11 power supply). The HDP is very detailed and transparent, with good sense of air and space, and offers a deeper soundstage than the Apogee headphone out. The HDP bass has great extension and impact, with rich mids and sparkly crisp treble. And it's just a little to the warm side of neutral, so I can still enjoy it with brighter headphones like my HD800 or Head-direct HE-5. Likewise it is also a good match for my HD600 headphones and my re-cabled Denon D7000 which can sound darker on the wrong amps.
Some amplifiers that are good with full-size headphones may not be a good match with very sensitive in ear monitors (aka earphones or IEM), and they might have noise, or hiss that is not otherwise detectable with full-size phones. Well, that is not a problem here. I find the HDP to be an excellent match with all my very sensitive universal and custom molded in ear monitors, including Monster Turbine Pro Gold, Westone 2, Westone 3, Westone ES3X, Ultimate Ears 11Pro and JH Audio 13Pro. It does a very good job with all of them, despite their widely varying sound signatures. The UE11Pro can sometimes be bass heavy or have some recessed midrange with the wrong amp; but neither of these are a problem with the HDP, even though it is not a bass-lite or forward sounding amplifier.
How they managed to squeeze such good sound into a price this low is unclear to me, because you basically have to spend $700-$900 for a better DAC (Apogee or Stello) and $700-$1,000 for a better amp (upgraded Woo WA6 or ALO Amphora), and you'd have to buy both a DAC and Amp to get most of the features of the HDP. (Except for analog inputs for iPod or other players, where many DAC's don't include those).
I will conclude by mentioning a couple of issues that I have. The HDP sounds very good with a wide variety of headphones, but it might not be optimal with all of them. With my Head-direct HiFiMan HE-5 and Grado HF-2, if I try to play those headphones at very high volume levels (closer to max) then the sound can get a little strident and fatiguing in the highs. I've heard this same thing with the HE-5 and a $700 Grahm Slee Solo SRG II, and that's probably because the HE-5 are very difficult to drive low impedance headphone and require a lot of current. With the HE-5 headphones this happens at volume levels that are much higher than my Woo WA6 tube amp can hope to achieve, so if I never tried to play the HDP louder than my WA6 I would not have heard this. The Grado HF-2 can be a little boosted in the upper mids and lower treble, and they just seem to respond better to my tube amps to tone them down a notch when trying to play them at very loud levels (levels that would be damaging or harmful for more than a few minutes). At normal to moderately loud levels this is never an issue.
Another issue is that the volume pot can have some channel imbalance at the very low end of the volume control when using very sensitive in ear monitors which don't require turning up the volume knob very much. This is common with most lower price gear when using IEM, but can be alleviated by turning down the computer system volume if you are using the USB input. However, none of these issues would prevent me from highly recommending this product. It makes me eager to think about trying their high-end products at some point.
