If Audio-gd is known for anything, it is for invading Head-Fi with a regularly changing series of units consisting of headphone amps and DAC all in one box. Back when a combined amp and DAC meant a severely sonically compromised unit with either a poor DAC or poor amp, Kingwa demonstrated that it was possible to do it with little compromise, but instead provides products where, simply, a higher price meant you got more hardware, better components, lower distortion and better sound. That can often making figuring out what to buy confusing as, very often, there is more than just one product at any price, the result of customers badgering Kingwa with ideas and his working hard to entertain them.
This means you can often decide to buy a DAC, but then are faced with the decision whether to buy the ES9018, WM841 or PCM1704UK version. Or do you get a unit with a built-in headphone amp? Or will it be worth getting one further up the range? And so on. Of the former choice in my example, the ES9018, Kingwa has been steadily perfecting his execution of this difficult chip. He described it akin to a Ferrari where you cannot use anything but the best parts or it won't work. Indeed his very first attempts at a low-end DAC/amp using it were far from perfect. Likewise, other DACs I've owned or tried that use the ES9018 can very often end up sounding flat and un-musical, leading me to wonder how they garnered good reviews.
The NFB-10ES2, the latest revision of a long-running $600-800 balanced design sits in the middle of the range, below the large all-in-one DAC/pre amps and the smaller, single-ended units. While balanced DACs were originally intended to reduce noise in pro audio on long cable runs, with headphone amps they are a design choice most often used as a means to increase power while keeping distortion down. Unlike other design choices however, balanced output affects the end user who must re-terminate their headphones. That doesn't mean that non-balanced-terminated headphones can't be used, as there is a regular headphone socket, but headphones that demand a lot of current, such as the latest crop of popular orthodynamics are going to benefit most from using the balanced outputs. Many are handily available with cables that have the necessary 4-pin XLR plug. For headphones that don't, if DIY is not your thing, there are many competent people or companies that will re-terminate your headphones for you or sell you a cable terminated for headphones on which the cable is detachable.
I asked for and received a review unit from Audio-gd so I could see how Kingwa's designs had progressed in design and sound quality over the previous WM8741-based unit I have.
Comparing my original WM8741-based NFB-10 "light case" model and the current NFB-10ES2, nothing seems to have changed externally. When Kingwa switched to the lighter cases from the heavier type he uses for his high-end gear he abolished the rotating volume control due to the frequency with which postal services seemed to break them. Indeed, it wasn't a volume control as such but a rotary encoder which adjusted a digitally-controlled series of relays that set the volume. The volume control was replaced with an up and down button instead, duplicated on the included remote control. This can make turning up the volume a bit slower, but the NFB-10ES will also remember your volume setting when switched off. Turning the unit on, the display will flash for a few seconds, during which time you can either hold down the "down" control to reset the volume to zero, or the "up" control to set it as it was before. The other front panel switches other than the power button respectively control whether the NFB-10SE sends sound to headphones or the DAC/pre-amp and a switch for low or high gain. Lastly, the "filter" switch, which was used on the WM8741 versions to change the DAC filter is used on the 10SE to change the brightness of the front panel between normal, dim and off. Kingwa has been in the habit of re-using cases for new products so this small mis-label is not such a surprise for people familiar with his products.
Around the back of the unit nothing has changed exempt for the addition of CE and FCC certification stickers. Input is via USB, coax S/PDIF (which can be optionally ordered with a BNC socket) and optical. USB is, unlike my old unit and it's Tenor chip, likely to be the best choice sonically as it uses the VIA USB receiver that has firmware where all functions other than those absolutely necessary for low-jitter digital transmission are disabled. It is also more reliable than the Tenor chips according to Kingwa, who has been known to cancel products if even a small percentage of customers were having serious reliability issues. The VIA USB receiver also supports up to 384 kHz input, if not DSD yet. Even if there are only a handful of files recorded at or near this resolution (equivalent to 8x over-sampled 48 kHz audio) it does allow you to run programs such as Audirvana (on a Mac) that can use top quality software to up-sample to this level (though when I tried up-sampling to 384k my Mac had a fit and I only got a weird noise. 192k was fine, however).
If your output isn't to headphones then you have a choice of standard single-ended RCA outputs or balanced XLR. By default the 10ES2 acts as a pre-amp, but by opening the unit and inserting a set of jumpers the unit can be set to act as a DAC with no volume control for the rear outputs.
The important bit.
In initially ran the NFB-10ES2 to my Adam ARTist 3 speakers•. Prior to burn-in I felt the 10ES has much the character of the previous model I have here. While a bit more forward and not as effortlessly spacious-sounding as my main rig, there was that attention-grabbing clarity I noted from the original NFB-10 along with the "younger" presentation of vocals one gets with the ES9018. Only because I have better equipment to compare it to (a Master 7 being the prime example) can I say it makes instruments sound a bit flat in comparison (or rather the Master 7 delivers a more lifelike presentation), but it is not something someone heading down the wallet-emptying path on Head-Fi would notice without having done the comparison. Indeed, in basic terms it sounded very good with nary a hint of digititis that I find annoying. However, NOS DAC fans may not agree. Regardless, further impressions require that I give the unit a good couple of weeks of run-in as the components are well-known to need it before the sound settles at its best.
Indeed the sound signature reminds me of the Calyx DAC 24/192 when I owned it and fed it an S/PDIF signal from the USB 32 version of Audio-gd's Digital Interface. It was as if Audio-gd's slightly "dark" house sound came from the DAC, compared to when I used the Audiophilleo 1. The Anedio D2, in comparison, sounded more detailed and less flat, but a little aggressive through the mid-range, especially with vocals and the bass was a little boomy. Given the Anedio uses bus-power for the USB input, there is an easy improvement available via a good USB bus power solution from any number of companies.
I'm sure at some point I'll be asked to compare the sound from the NFB-10ES2 to the Master 7. The NFB-10ES is like watching a movie of a band playing on a HDTV. The Master 7 adds a very distinct degree of 3-dimensionality, detail and depth to the sounds, making instruments on the 10ES sound more flat in comparison.
Where the NFB-10ES really shone was using the USB32 input and feeding my Emotiva Airmotiv 4 active speakers. While I initially fed it using the optical input from my TV, which is connected to an Apple TV, the USB32 input fed by a computer or streaming music through my Raspberry Pi was a distinct step up. If you want a basic speaker rig for under $1k that sounds great, it makes for a good combination, with only the speakers lacking in the low bass region.
One of my favourite audiophile recordings, Friday Night in San Francisco, which has some of the fastest and most amazing guitar work I've ever heard was no trouble for the NFB-10ES2, either as a DAC, pre-amp or any of my headphones. Indeed, one of the criticisms of previous models was that they were either very dark-sounding or too aggressive, which was fine with orthos but less so with other headphones. I gave the 10ES2 a run both balanced and single-ended with Audeze LCD-3 (low impedance, current-hungry and dark) and my old MB Quart QP 400s (high impedance, high voltage-swing desiring and bright) both out of the balanced and single-ended sockets.
The result I felt was good in both cases, neither demanding pair of headphones suffering from a lack of soundstage, even if the amount of power available out of the single-ended socket is considerably less. Ideally the amp is supposed to be used in balanced mode.
David Chesky's awesome binaural recording of Amber Rubarth took up duty when it came to determining detail and resolution. While instrument notes weren't as layered or detailed as out of the Anedio D2 or the other high-end DACs I had on hand, they were delivered with a lack of fuss in comparison (the D2 can sound a bit forced at times). If anything, the NFB-10ES2 has a purely listenable quality about it, that is, rather than analyse the sound I just wanted to listen.
I also tested the NFB-10ES2 with the best IEMs I had on hand from the SE output using a 3.5mm adaptor. The result with both my JH-13s and a pair of Tralucent 1plus2s was excellent with a totally silent background and the music coming through clearly.
So, overall, if you're after a neutral and very IEM and headphone-compatible all-in-one unit for $680, the NFB-10ES2 is a worthy contender, especially if you want to also have a DAC and/or pre-amp to go with active speakers. Probably the greatest disadvantage is that, to get the most out of it you ideally need to re-terminate your headphones to a 4-pin XLR for the balanced output. If doing so is something you're not willing to do and you're not otherwise going to use it with active monitors, one of the single-ended models will probably be a better choice.
*Not headphones because my son had fallen asleep on me and he wakes up if the music is turned off!