Found this review on Amazon.
It seems that getting a hold of one of these at list price on Amazon is not an easy thing to do (at the time of this writing), so after looking around on the web I've managed to get one (for a reasonable $129 shipped) from a FiiO authorized dealer: Sonic-Electronix. Now, I should start with a disclaimer: In general I don't like (spending money on) portable hi-fi audio gear, and that for two reasons: (1) Portable gear is often resource limited (space, power, etc.) and the designs involve all kinds of compromises (power vs. accuracy, size vs. mechanical durability, etc.) and (2) Listening to music on the go, in transit (a car, bus, train, plane, etc.) or any other public places is often marred by so many other spurious noises that the advantages of using hi-fi audio gear are often negated. Nevertheless, I needed a good headphone amp with some bass-boost capability for home use (to improve the sound of the Sennheiser HD-598 headphones when used with the Onkyo C7030 cd-player) and none of the desktop amps in the $150-300 range have that (bass-boost) feature. So, after looking at some of the portable/transportable amps out there (from JDS-Labs, C&C, Fiio, iBasso, Leckerton, Matrix, SMSL, Little-Dot, Meier, MicroShar, etc.) I decided to try this new offering from FiiO: E12 - The Mont Blanc.
Bulid quality: The Fiio E12 is encased in a machined aluminum box (about the size of a smartphone) with a brushed, black finish. On it, the adornments are fairly minimal: a semi-recessed volume knob that doubles as on/off switch, two 3.5mm jacks (in/out), and a bunch of recessed switches: voltage gain (0dB, and 16dB or 6.4x), a cross-feed (to change the feel of the sound stage), the bass-boost, and a micro-B USB plug for charging. The front face also has two small LEDs: a red blinking one to indicate charging status and a blue one for power-on. Overall I'd rate the build quality as top-notch. The volume knob turns smoothly but it requires some effort (presumably to prevent accidental changes), the switches can be moved easily (though the gain and cross-feed are somewhat hard to get to), the jacks feel solid and there are no loose parts. Aside from the USB charging cable, FiiO has also included a 3.5mm to 3.5mm adapter cable (a bit short for desktop duty but perhaps long enough when used on the go with a portable device), two heavy-duty rubber bands, some stick-on rubber feet, and a black carrying pouch.
Before I move on to sound quality (SQ) and the comparisons with other audio gear I have here, I should say that in the end, I wound-up using it in my desktop/computer setup despite it being a very good match (SQ wise) for the HD-598/C-7030 pair. The reason is (and interestingly enough) quite mundane: the Sennheiser HD598 is fitted with a 1/4in jack. To use it with the FiiO-E12 an adapter to 1/8in (3.5mm) jack is needed (I used a pigtail type adapter to reduce mechanical stress) but the whole thing was ridiculously bulky, cumbersome and awkward to use, so I gave up on using the E12 that way (for fear I may stress or damage the E12 output jack by mistake). So, what follows are mainly conclusions from using it in the desktop setup with my two other cans, the ATH-A900 and the HD681.
Computer/audio gear used during my listening tests:
MacBook-Pro w/ Mac OS X 10.6.8
XMOS USB 2.0 Audio Reference Design Asynchronous DAC,
HiFiMeDIY Sabre USB DAC,
Matrix M-Stage Headphone Amp,
FiiO E12 (after 6-8hr burn-in and recharge)
Audio-Technica ATH-A900 closed-back headphones (40 ohm),
Superlux HD-681 semi-open headphones (32 ohm), and
Sennheiser HD-598 open headphones (50 ohm).
Playback software: Audacity, iTunes, VLC
Source quality: standard CD 44.1kHz/16bit, and native HD 96kHz/24bit
Audio cables: 3.5mm to RCA 3ft, AUVIO and Monoprice brands
The Sound (overall conclusion, both DACs, all headphones): Clean, mostly neutral (slightly warmish), with a good high end (a little rolled-off maybe?), a fairly forward but engaging mid-range, and (what I think is) a fantastic (and I really mean FANTASTIC) low-end (with bass-boost either on or off). Staging is pretty good (the forward mids seem to obscure this somewhat, which has led some reviewers to claim that the sound stage is constricted/narrow, but I think it's actually okay.) Nevertheless, this amp will favor or pair better with open/semi-open headphones. With my headphones the E-12 is hiss-free on 0dB gain, with some hiss becoming audible on 16dB gain at and near maximum volume. Channel balance is very good even at very low output levels. Extremely powerful.
To put all this this in some perspective, let's look at some comparisons. With the computer sound-card? No, I'll waste no time here comparing this amp with the sound card in the MacBook-Pro, there isn't any fight to be had there. How about the headphone amp in the Onkyo C-7030 cd-player (mentioned above)? some might wonder. Well, the hp-amp in the cd-player actually fares a little better than the computer but isn't much of a challenge either (see a few more details below). Instead I've pitted the FiiO against the redutable, A-class biased M-Stage desktop amp from Matrix Electronics. First, a look at how the technicals stack-up:
FiiO E-12
Voltage gain stage: (TI Op-Amp) LME-49710
Current buffer: (TI Op-Amp) LME-49600
Gain: 0dB, 16dB
Bass boost: 5dB @ ~70Hz
Input/Output impedance: 5 kOhm/0.5 Ohm
Max. output: 15.5Vpp
Input overload: 8Vrms (0dB gain) (mfg. spec)
THD/(S/N): -94dB/-110dB (unspecified condition)
Power: 11.1V (3x3.7V Li-Ion battery) w/ USB charging
Circuit config: +/- rails, virtual ground (pump-charge negative rail)
Volume: Analog - Alps pot
Input/Output: 3.5mm/3.5mm jacks
Enclosure: Aluminum
Matrix M-Stage (stock v. 2011-2012)
Voltage gain stage: (TI/Burr-Brown Op-Amp) OPA-2134
Current buffer: Discrete, 2 x FET/each channel
Gain: 0dB, 10dB, 18dB, 20dB
Bass boost: None
Input/Output Impedance: 47 kOhm/5 Ohm
Max. output: 22Vpp
Input overload: > 5Vrms (0dB gain) (measured)
THD+N: -100dB @ 6mW/300Ohm
THD+N: -95dB @ max. output
Power: audio grade toroidal transformer + rectifier, regulated
Circuit config: +/- rails symmetrical, physical ground
Volume: Analog - Alps pot (Blue Velvet)
Input/Output: 2xRCA(line)/ 1/4" jack + 1xRCA preamp-out
Enclosure: Aluminum
The first thing I noticed when switching from the M-Stage to the E-12 was a remarkable improvement in bass-response and bass impact. With my two low-impedance (32-40ohm) headphones (the ATH-A900 and HD-681) it really is no competition there, with the E-12 clobbering the M-Stage (well, more or less). The M-Stage has an output impedance of 5 Ohm, and the relatively low impedance (of those headphones) yields minimal damping in the system, leading the M-Stage to a somewhat tenuous, borderline control over the headphone voice-coils for low-frequency, high amplitude motion. The E-12, with its 0.5 Ohm output impedance sees an order of magnitude increase in damping factor, and this lends it an iron-fist control authority over those voice coils and ultimately enables it to render the bass with (for lack of a better word) stupefying precision. The situation is less clear-cut when using the Sennheiser HD-598 since these, although rated at 50 Ohm/1kHz, do have a large bump in impedance at bass frequencies (to more than 300 Ohm), so the M-Stage does considerably better with them (though I'd still give the nod here to the E-12 when it comes to bass impact, even when the bass-boost is off). When it comes to mids, the two amps are largely similar, though the more forward sound of the FiiO seems to put it at a disadvantage. By comparison (and when one considers the percieved narrowing effect this has on E12's soundstage) the M-Stage sounds a bit more expansive while retaining a better composure, or rather, a little more refinement. The E12 has a tad more warmth, likely owed to its higher THD (about 6dB more than the M-Stage) throughout that range so, perhaps unsurprisingly, the M-Stage is the more neutral/superior amp there in technical terms as well. When it comes to highs, I'd say the M-Stage does slightly better also. Can't put a finger on it, but all else being equal (including volume level) I find that I prefer the high end on the M-Stage. It is perhaps that the E12 at times seems to accentuate the graininess of the sound in the upper registers (in general, but especially for 44.1kHz/16bit playback). Regarding the attack and decay, I find the two amps to be fairy well matched. Powerwise, the M-Stage is the more powerful amp (with a max. voltage output of 22Vpp vs. the E12 at 15.5Vpp) but make no mistake, the E12 will put out a massive amount of power, which should be more than enough for most headphones (except perhaps for the most inefficient low impedance plannars). So, considering all this, if (hypothetically) I were forced to chose one of these amps which one would it be? Well, all things considered, despite the terrific low end of the FiiO and its very good overall sonic performance I would go with the M-Stage. (But, if I could have my cake and eat it too then I'd definitely get both.)
A note on battery life: after recharging, I've used it for about 6hr at low to medium power (with 0dB gain) and is still going. So, battery life seems pretty decent. The cross-feed feature is there but I did not find it particularly useful - it just further reduces the width of the sound stage without any other benefit (that I could hear).
Compared to the headphone amp on the C-7030 (JRC Op-Amp 2 x NJM-4580D/ symmetrical power rails + physical ground/ linear, regulated power supply) the FiiO E-12 is clearly superior. The cd-player headpone amp is fairly good for what it is but it sounds somewhat thin in the bass, and a little constricted/congested throughout the mids. The highs are pretty good and staging is decent but overall, especially with bass shy headphones (such as the open-back Sennheiser HD598), the entire listening experience leaves you wanting (hence my original motivation to look for an amplifier w/ bass-boost). The FiiO E12/HD598/C-7030 combo is (I think) a very good pairing but because of the whole 1/4in jack issue with these headphones (as mentioned above) I can't really recomend the E12 be used in such a fashion to anyone (and I don't think that I'm a particularly clumsy person but that kind of cumbersome connection between audio components is an accident waiting to happen). However, my other headphones (which have 1/8in jacks with screw-on 1/4in adapters) do work just fine in that configuration. Overall, for my desktop setup, I settled for the following with very good (and nearly identical) performance: MacBook-Pro/XMOS-DAC/FiiO E12/Superlux HD-681 (slight EQ - the Superlux have excessively bright highs), and MacBook-Pro/SABRE-DAC/M-Stage/ATH-A900 (some EQ). The Sennheisers are more versatile as they seem to work equally well with either amp/DAC combination with some bass-boost.
To conclude, E-12, the latest (and perhaps greatest) headphone amplifier from FiiO, and which uses two of the newer high-end TI audio op-amps is a well built, great sounding little amp and I'd say (though I haven't listened to everything else out there in its price bracket) a good deal at list price (here consider that the M-Stage sells for twice as much). If I were to sum up the FiiO in one word I'd choose - FUN. The E12 is a fun sounding amp, and definitely the cure for boring sound. For whatever is worth, given my ingrained aversion to portable audio gear, the Mont-Blanc made a believer out of me: good things do, sometimes, come in small packages - so, no doubt - 5 star.
UPDATE 05/30/2013: Some further thoughts after 3 weeks of nearly daily use -
Battery life: 12-14 hr on a full charge on 0dB gain at low to medium volume with the 32ohm HD681. The amp will automatically shut-off when the battery charge drops below a certain level (I'm assuming the power monitoring/smart-charging chip in the amp does that to protect the battery (and the electronics in the amp) from damage if the battery voltage were to drop too low. Charging time is 6-7hr when using a regular (500 mAmp) USB port on my computer. Apparently the amplifier can be used while charging but I have not tried it, since, with the battery depleted the amp would, essentially, be powered directly from the USB and that type of power coupling to a fully loaded USB power port (and that, through a 5V to 11V boost converter too) can't possibly do anything good to sound quality.
SQ: After an additional 20-30hrs of use the mids seem to have pushed back a little and the high end has smoothed somewhat. As a result the sound stage feels a bit more expansive than it did initially and the perceived slight roll-off of the high end is now gone (if it actually was there to begin with). It may be that this is just myself having gotten used to the sound of the amp but I'm more inclined to think that these subtle changes are, in fact, real since the E12 now (by and large) seems to have closed the overall SQ gap with the M-Stage while holding on to its better low end. While I cannot comment on its performance with power hungry cans (consider here that the negative rail is artificially produced, most likely by switching a capacitor - i.e. pump charge, and high current demands by difficult loads may lead to uneven rail voltages, distortion, leakage of the high frequency pump-charge switching noise into the audio-path, etc.) with my very efficient (98-101dB/mW) 32-50ohm cans the E12 is nothing short of remarkable.
