I’m the guy who started this thread with a preview look at a NuForce Icon Mobile prototype. I waited till NuForce started shipping the Icon Mobile in black to buy one myself, but I’ve had it now over a month. I thought I’d add a few thoughts to this excellent thread based on many hours of listening to the production version.
I started using portable headphone amplifiers over a decade ago because I found portable CD players (remember them?) unlistenable. In my experience, they even got worse over the years. I went through three generations of Headroom’s AirHead, each noticeably better than the earlier. Meanwhile, ironically it took a computer company to produce portable players with listenable audio. The iPhone 3G with lossless music sounds pretty darn good, a clear advance even over my 5.5G iPod. (I can’t retire my 5.5G any time soon, however, given how little data space for lossless music there is on an iPhone.) But a good headphone amp can still improve even the 3G. I can’t comment on the impressive arsenal of amps HA has tested, only the Total AirHead.
My initial listening suggested that if you put “audio quality” on a linear axis, the Total Airhead would land about half way between an un-amplified iPhone 3G and the Icon Mobile. My assessment has not changed. The Mobile Icon really stands out in terms of clarity and dynamics. I cannot confirm S/N of 98dB and THD+N at 0.054%, but listening makes those claims seem credible. I’m particularly impressed by how clear back-up voices and instruments sound, music that gets lost without the amp. I can hear room echoes that are just not there on the AirHead. On the high-gain setting with max volume and no signal, I can just barely hear the noise floor.
The Icon Mobile also noticeably improved dynamics. Attacks sound crisp but not exaggerated. The naked 3G and the AirHead sound a bit muddy in contrast, especially the naked 3G. But at something like 1/10 the volume and 1/10 the weight of the AirHead (and cheaper than a BitHead), frankly, the Icon Mobile didn’t have beat the AirHead for me to retire the latter. Better sound quality is a bonus on top of that.
For perspective, I did compare the Icon Mobile to my home stereo, a PS Audio Digital Link3 DAC and Rotel RC1082 pre-amp with a rather nice built-in headphone amp via USB. In sum, you won’t see my DL3 or RC1082 on eBay any time soon. The Mobile Icon just doesn’t have the effortless air of my home system, not that I expected it to. I suspect the biggest advantage of the home system is the DL3’s jitter filtering (with an ASRC), but I have no way to test that.
There are two features contributing to audio quality in the AirHead I will miss, and maybe NuForce can consider them for “v2.” Since most music is balanced for room listening, the AirHead rolls off the high end just a bit to get rid of some over-brightness. Second, the AirHead can cross-feed attenuated, delayed signals to each channel to noticeably improve staging and so the musicians don’t sound like they’re trapped between your ears.
The Icon Mobile definitely sounded better the more I listened to. I can’t deny the phenomenon of burn-in, as I’ve experienced it myself. Jason Lim at NuForce told me the non-audiophile employees in Taiwan on the Icon Mobile production line have noticed the phenomenon. But because I have yet to hear a physical explanation of how a solid state electronic component can change its sound quality over a relatively short time frame, I have to give credence to an alternative hypothesis that this genuine phenomenon is really a psychological process of familiarization. Seems there is a great experiment just waiting to be run by some psychology student with audiophile interests. If any of you have physical explanation that’s credible (e.g., skip the story about capacitor aging), I’m all ears.
I agree with HA that the Icon Mobile should be more than adequate to drive any in-ear monitor. I found it more than adequate on high-gain with my AKG K701s for any of the music I listen to. I tried an old pair of AKG K340s (passive electrostatics). They sounded surprisingly good with the Icon Mobile, but I think there would be times I’d want more volume. So your mileage may vary on whether or not the Icon Mobile can sufficiently drive a particular full-sized headphone.
The Mobile Icon is dramatically less sensitive to EMI from GSM mobile phones than the AirHead. This probably is due to the much higher level of integration into silicon of the Mobile Icon than any special shielding effort in the NuForce design, but the net effect is to reduce the impact from screams of auditory pain to “mere” annoyance and a rare one at that. The Apple did a dramatically better shielding job in taming the EMI beast with the iPhone 3G than Palm and BlackBerry did with the Treo 650 and Curve I’d previously owned, respectively. Still, I took HA’s lead and bought some inexpensive EMI shields from Quick Bridge (
Quick Bridge Solutions - EM Shield for iPhone) They definitely work and do so almost all the time; EMI is no longer an issue. (Be sure you place them on the back of the iPhone, not the front, as Quick Bridge recommends.)
NuForce did a nice job on some of the physical details of the Mobile Icon as well. I often use my mobile system outdoors, running, yard work, or whatever. Moisture and dust are unavoidable. I had a lot of problems with switches and volume pots on my earlier two AirHeads (though not the current version). But I like the fact that the Mobile Icon just deleted the on/off switch as unnecessary. And the volume pot feels and behaves like a precision device unlike what is typical for consumer portable audio. The LED lights were also well thought-out. I like the fact that there are separate lights for USB power and USB link.
