Pros: Great overall sound, 3D soundstage enhancement, xBass bass boost
Cons: Hiss on sensitive headphones (can be corrected with a new attenuator available soon from iFi), large size for a portable
I wrote a review on here a while back of the larger micro iCAN amplifier (http://www.head-fi.org/t/654405/ican-amp-review-a-new-amp-that-gives-you-more-more-bass-more-soundstage-and-more-detail), and recently Vincent from iFi asked if I wanted to try out their smaller Nano iCAN amp. So Avatar Acoustics, their US distributor sent me a Nano to try out. Here are some impressions mostly taken from the comments I made about the Nano in the thread of that longer review of the larger iCAN:
I had my first listen to the smaller amp after letting it burn in overnight with my Isotonic CD. It is a wonderful baby brother to the bigger iCAN. The same overall sound signature and of course the great enhancements of the 3D and XBass features (see the longer review I linked to above of the original iCAN for more details of these features). It does not quite have the same authority as the bigger iCAN as should be expected at half the size and 3/4 the cost. The bigger amp just takes a little firmer control of the headphones and gives a little more body to the sound.
The smaller amp also has only one setting for both the 3D effect and the bass boost. The one level of bass boost seems to be about the same as the lower setting on the larger iCAN, and the single 3D setting is a slightly more subtle version of the three dot 3D setting on the larger iCAN. (Vincent at iFi has confirmed that the 3D setting is a more subtle effect than on the larger iCAN and is sort of halfway between the one dot and three dot settings on the larger amp. With more listening, I find I like this new setting on the Nano even better than the settings on the larger iCAN. It sounds more natural to my ears.)
The difference between the two amps is surprisingly slight, but this was with the Sony MDR-MA900 headphones which are not very demanding. It is possible that the difference would be greater with headphones that are a heavier load on an amp. Unfortunately, I do not currently have any more demanding headphones as I have been whittling down my collection.
I was also able to compare the Nano to the Mini-Box amp card in the Hifiman 802, which is a $250 add on to the 802 ($200 if you buy it at the same time). It has a good reputation as it is based on the OPA627 OP-AMPS. But compared to the Nano iCAN the MIni Box card sounded a little closed in and muffled. Once you turn on the 3D effect and the xBass on the Nano, it pulls away and is simply cleaner and more spacious sounding, while also having more body and low end oomph. Quite a nice showing for the $189 Nano to outperform the $250 Mini-Box amp card.
One downside to this smaller iCAN is that with very sensitive headphones, there is a very noticeable hiss. I just got in a pair of JVC HA-FX850s which I am loving. But they are not a good match with the Nano because of the hiss. The hiss is there even with the Nano amp set to the lower gain settings using the switches on the bottom of the amp. Of course, it is not noticeable when music is playing loudly. But, I listen to a lot of simple acoustic music and so I could always hear the hiss in the quieter passages and silent pauses. As much as I enjoyed the sound of the Nano with the JVC's, I am not going to put up with hiss in the long run. So since the JVC's are definitely keepers, the iCAN Nano is going back to Avatar.
NOTE ADDED: Vincent at iFi has suggested that some new attenuators that they will be offering may solve my problem with hiss. They go between the amp and the headphones and reduce the sound by 12 or 24 db to reduce the hiss and also give a more usable range to the volume control. So Avatar is going to send me the Nano amp again once the new attenuators are in stock, and I will update this review to report on my experience with the JVC iem's and the Nano using some attenuators in the signal path. I will be very glad if this does solve the problem as I would love to have a portable sized iCAN that works with the JVC's. (It also seems that if these attenuators do not negatively affect the sound, they could be a useful product with any amp/headphone combination that produces hiss.)
Summary: If you do not use high sensitivity headphones, then the iFi Nano iCAN amp is a great, more portable version of the iFi sound, with similar features to the larger iCAN amp. It is not the most portable of amps, more of a transportable type of amp as it is a little bit bigger than the size of a deck of cards. The battery inside the Nano is rated for 70 hours, so it does take advantage of being bigger than some portable amps by including a long lasting battery. The lower price of $189 makes it a viable option for someone wanting to try out the iFi sound and features in a more portable size. And read on to learn how the attenuators solved my hiss problems and would make the Nano a good match even with high sensitivity headphones.
Addendum added April 22, 2014:
I just received a couple of attenuators from iFi for use with the Nano headphone amp after I reported in this review that it had noticeable hiss with my JVC HA-FX850 iems. (Disclosure: Vincent at iFi told me I could keep these attenuators, as they are not yet for sale and he did not think it was worth my while to ship them all of the way back to England. I do not have any financial relationship with iFi or any of their distributors.)
They are a simple and well made wired pair of 1/8 inch headphone jacks (one female and one male) that you use between your headphones and the amp to reduce the volume and the SNR. Vincent posted a very thorough explanation of how the attenuators work to reduce or eliminate hiss on my review of the larger iFi iCAN amp here: http://www.head-fi.org/t/654405/ican-amp-review-a-new-amp-that-gives-you-more-more-bass-more-soundstage-and-more-detail/345#post_10448027
He sent me two versions of the attenuators: one with 12db of attenuation and one with 24db. Here are some pictures:
Briefly put, when used appropriately, they work great at both reducing hiss and giving a more usable range to the volume control when combining high sensitivity headphones with iFi's amps.
The 12db attenuators eliminate 90-95% of the problem with the hiss on the Nano amp when using my JVC iems with their sensitivity rating of 106db/1mW. In fact at normal volume, there is almost no audible hiss. It is only if I turn the volume all of the way up (with the music paused) that I still hear any bothersome hiss. It also gives me a much more usable volume range on the Nano amp. Before, I could barely turn the volume up above the lowest position where there is sometimes some channel imbalance. Now, I can use the volume of the Nano between 11:00 am and 1:00 pm, when using the line out output of my new DX90 DAP.
The only slight effect besides eliminating most of the hiss that I hear is a very slight smoothing of the sound which I actually like in my setup. It is an extremely small effect, and again I like it in my system, although it is so small that I can't even be completely sure I really am hearing a difference. Lee370 on here told me he has used attenuators in the past that took the life out of the music. I do not hear anything like that in my setups with both versions of the iCAN amplifiers, but as always your mileage may vary. (Note added: Vincent at iFi told me the following in an email: "We use a particular type/brand of resistor that is very adept at carrying the signal. If one uses normal resistors, they most definitely do take the life out of the music.")
The 24db attenuator eliminated 100% of the hiss even at full volume on the Nano, but it created a problem with the Nano amp in that I started experiencing distortion at volume levels just above my normal listening level. It seems the 24db attenuator presents too large a load to the Nano amp. I did not have this problem with the 24db attenuator on my larger Micro sized iCAN amp, but then again I would not ever need the 24db attenuator with the larger iCAN as it has less hiss to start with.
Also when using the 24db attenuator with my Altmann Tera player (which has a lower output level than the DX90 line out) as a source feeding the Nano amp, the 24 db takes out too much volume and I end up maxxing out the volume on the Nano on quieter tracks, and am left wanting for volume. So if you have a source with relatively low output power, you may be limited to using the 12 db attenuator.
I also found the 12db version works great with the bigger iCAN, which has much less hiss to start with, and no hiss at all even with just the 12db attenuator. Of course I can also easily use the 24db attenuator with my bigger iCAN Micro amp, but it is not necessary with my headphones. The 24db version might still come in handy with an extremely high sensitivity headphone like some of the Sennheiser iem's that go up to 125db/1mw, but in general I found the 12db version to be all I needed. And again, using the 12db version did not cause any problems with distortion with the lower power Nano amp, at least not at anything close to normal listening levels. So, in general it seems the 12db version may be the more universally useful one, but in extreme cases the 24db might also be useful, i.e. when using very high sensitivity headphones. I did not have any extremely sensitive headphones on hand to adequately test the usefulness of the 24db version.
However, I did find the 12 db attenuator also worked well with my full sized Sony MDR-MA900 headphones which are rated at 104 dB/mW and which have a little hiss on the bigger iCAN amp. However, I encountered the distortion problem with the 12db attenuators and the Sony's when I used them on the Nano. I am not sure why that happened as it does not happen with the higher sensitivity JVC's and the 12db unit on the Nano. It might be due to the impedance compensating circuit built into the Sony headphones, and how that circuit interacts with the added impedance of the attenuator.. But it does seem that at least sometimes, these little attenuators could also come in handy with high sensitivity full sized headphones. I am particularly sensitive to hiss and so it bothers me a lot when an amp adds hiss to the sound. I wish I could have had one of these iFi attenuators around all of these years. With all of the different combinations of headphones and amps I have tried, there have been plenty of times when they would have come in very handy.
Please note that the attenuators only reduce the hiss that is created by a higher powered amp feeding a pair of headphones with high sensitivity as they reduce the noise floor so the hiss becomes inaudible. However, they do not reduce or eliminate hiss that is found in the recording itself, such as older analog recordings that have tape hiss in the background. That type of noise is not affected by these attenuators.
Ifi is earning a well deserved reputation for creating gear that outperforms its price, and also for creating unique products that serve a particular niche such as their iUSB power supply and iTube tube buffer/preamplifier. These new attenuators are just such a useful niche product that can be used with their amps where hiss or limited volume range is a problem. Unfortunately, they are not available yet, but iFi does plan on making them available for sale through their dealer network to all purchasers of their amps to accommodate people who want to use high sensitivity headphones with their line of amps.
Surprisingly, iFi does not currently have plans to make them available as a stand-alone product. I think they might be missing an opportunity as it seems these little accessories could sell well and be very useful with a wide range of amps and headphones. It might not be a high enough profit margin for it to be worth their while, but maybe if enough people on here let iFi know if they are interested in buying these, they will reconsider.
Two more general notes to add to this review of the Nano: While it is still burning in, I am really enjoying my new DX90. The amp in the DX90 is very close in sound to the iCAN Nano. I still have to give the slightest edge to the Nano as the 3D effect is hard to live without. But the DX90 has so much detail and instrument separation, that I miss the 3D much less with this DAP than I did when using the Hifiman 802 with the Mini-Box amp card. That the DX90 sounds so close by itself makes it even harder to decide if I will keep the Nano or not.....UPDATE: After going back and forth a lot today, I am going to keep the Nano amp. There is something addictively natural and relaxing about the sound with the 3D engaged on this amp that the DX90 alone just cannot match. The combination of the DX90 as source and Nano as amp is the best of both worlds: the detail and clarity of the DX90 with the natural spacious soundstage of the Nano, and also the xBass boost when needed to warm up the sound. Even with the JVC HA-FX850 which are not lacking in bass, I find I leave the xBass turned on most of the time. The boost is completely in the lowest frequencies, so it does not mess up the mids. And there is more to having plenty of low bass than just giving bass heavy music a kick, as explored here: http://www.head-fi.org/t/672810/bass-boost-affects-more-than-bass
Also, I discovered the Nano has a similar problem to the larger iCAN amp. The 1/8 inch input on the back of the amp is very slightly recessed, so when using a mini to mini interconnect with large plugs, the cable does not seat fully and so one of the channels cuts in and out when the cable is jiggled. It happens with only one of my mini to mini cables, but it is helpful to be aware of the problem so you do not think there is something wrong with your amp.