About a year ago I was approached to provide some early feedback on a new multi-bit (discrete R-2R) DAC. It didn’t have a case. It didn’t have a projected price. It didn’t have a release date. And it didn’t have a name - simply being referred to as “RDAC”.
First impressions were distinctly positive, even compared to some of the stalwarts in this space, to the point I was quite anxious both to learn what it might be sold for and to hear how the final iteration was going to perform. So, when about a month ago I was offered a unit with the final production electronics, properly cased, and ready to be subjected to a formal review, I jumped at it.
Today the veil comes off and what is now officially called the “
Massdrop x Airist Audio R-2R DAC” (or, “RDAC” for short) is public and being formally offered for sale, at $349.99, starting on June 6th:
Major Features
The interesting features of the RDAC are buried inside the unit - the exterior being an unassuming, but stylish matte-black housed in a chassis that stacks perfectly with the Massdrop x series Cavalli amplifiers:
- Dual 24-bit discrete R-2R ladders, per channel, in sign-magnitude configuration.
- Bit-level buffering/isolation on the ladder resistors.
- Separate PCBs for the resistor ladders vs. I/O, conversion and other processing.
- Internal power regulation and reference voltage stabilization.
- Low phase-noise NDK clocks.
- Custom decoding and filter implementations.
- USB (galvanically isolated) and S/PDIF (COAX and TOSLink) inputs.
- PCM native conversion up to 24 bit/384 kHz.
- DSD support to DSD128 (via internal PCM conversion).
Listening Notes
Critical listening was done with the RDAC being driven via it’s USB input (after determining this was the best way to drive it in my system) via Audirvana+ and Roon. Source material was primarily 16/44.1 FLAC format CD rips, with some native high-resolution content and multi-rate DSD albums to test those capabilities.
Primary listening was performed via an iFi Pro iCAN and a Woo Audio WA234 MONO Mk2, with some additional amplifiers included for pairing/system matching commentary. Headphones ranged from the HD650 to the Focal Utopia and Abyss AB-1266 Phi.
Direct comparisons were performed in a hardware assisted blind(ish) fashion. Not strictly a fully blind comparison, but a lot closer than simple sighted listening.
How Does it Sound?
The TL;DR; here is simply that the RDAC sounds
marvelous.
The signature is one of general neutrality with a touch of sweetness to the mid-range and upper registers, and a distinctly “pristine” quality/clarity to the sound. Overall presentation is open with a good sense of air but is neither lacking, nor carrying too much, tonal weight/density. The RDAC’s rendering is fluid, articulate, nuanced and well balanced - capable of excellent top-end delicacy while simultaneously plumbing a tuneful, driving, bass-line and keeping vocals present and lucid.
The strongest, and most enduring, comparison I can make for the Massdrop x Airist Audio R-2R DAC is that, at least from a signature perspective, it sounds like a Holo Audio Spring DAC and Soekris dac1541 got it on - and this was the result. It exhibits some of the sweetness that I found so beguiling with the Spring DAC combined with the distinctly “pristine” quality to the sound rendered by the dac1541.
While the RDAC is not quite on the same level with all technicalities as those two units, it’s surprisingly close and the combination of their better sonic aspects results in a very compelling delivery with a broad variety of music.
In More Detail
Tone is lovely and pure, with just a hint of sweetness. I’d stop short of calling the presentation romantic or euphonic. There’s just enough “sugar” to keep the otherwise “pristine” or “super clear/resolving” delivery on the “musical side” of things vs. drifting off towards being “analytical” and is, for me, a more engaging listen because of it.
Extended sustain on piano notes, from my own pieces, exhibit none of the strange tremolo or vibrato that I’ve found in some other discrete R-2R DACs that would be considered natural competitors to the RDAC. Here … the tone remains pure until the notes naturally ebb away.
Timbre is natural and realistic. Instruments are easy to identify reliably, even in very complex orchestral works and when they’re separated by relatively minor familial differences, purely by how they sound (without resorting to locational cues). Individual oices, similarly, are easy to identify and localize, even when faced with multi-part close-harmonies.
Transient performance is excellent, almost NOS-like in fact, with plucked strings, discordant brass and aggressive percussion all exhibiting surprisingly rapid and impactful attack/bite. Switching to electronic music and the impact and transient speed remains … play the first 60 seconds of “The Rat” (Infected Mushroom, “Army of Mushrooms”) and you’ll see what I mean. Or run something like “Along this Road: Kono Michi” (Ottmar Liebert, “One Guitar”) and the instant bite of the pluck and the reverberant decay against a deep, dark background.
As I’ve said, there’s a hint of sweetness to the delivery of the Airist Audio R-2R DAC - and this is most in evidence in the mid-range. Lucid and transparent are also terms that come immediately to mind here. Vocals, particularly female, are present, well articulated, and unexaggerated. There’s no apparent emphasis or reticence. Just a natural, emotive, and evocative rendering.
Something like “Ellis Island” (Mary Black, “Looking Back”) showcases this sweetness quite nicely. And being a semi-sweet piece in its own right helps to show when this sort of sound is taken too far … and with the RDAC it is not - it’s just where I like it.
The upper registers are clean, smooth and properly extended, carrying some of that mid-range sweetness forward in a Goldilocks-like “Aaahh … just right” fashion. There’s a palpable sense of air and space and a very honest delivery. If there’s sibilance or harshness in the source material it’ll be reproduced faithfully, without ever exaggerating or exacerbating it. Cranking various pieces by “Heart” or “Julia Fordham” can be a bit of a wince-inducing torture test in this regard but were handled with aplomb by the RDAC.
Playing a couple of “guilty pleasure” tracks here, specifically, “Buffalo Girls” and “Double Dutch” (Malcom McLaren, “Duck Rock”), through the RDAC shows that it is not going to gloss over faults or harshness in a recording (and you can hear well into the aggressive edits/mix of, say, some of Prince’s works) but it
won’t make them worse either!
At the opposite extreme, the bottom octaves, while perhaps not the absolute last-word in terms of low-end drive and slam, are only marginally behind the front-runners there and the RDAC certainly isn’t lacking in the bass-department. Playing some more bass-intensive tracks (Beyoncé’s “Partition” or Trentemøller’s “Chameleon”) shows no lack of weight, and excellent texture, speed and articulation. A run through Talvin Singh’s collection “Anokha: Sounds of the Asian Underground” is, similarly, fully satisfying.
Stage is quite convincing. I only got to test this with headphones but even so the RDAC is capable of projecting a realistically wide stage, and the “sense” of space in a given venue is very well communicated - play something like “Mining for Gold” (Cowboy Junkies, “The Trinity Session”) and you’ll be subjected to a distinct sense of the simple, stark, natural environment the recording was made in.
Layering and separation are typically strong points of R-2R implementations for me, and the Airist Audio R-2R DAC is no exception. Picking out individual instruments in a complex mix is easy as is tracking the melody while tapping your foot along to the baseline (which you’ll be hard pressed not to do).
As mentioned initially, there’s a distinctly “pristine” aspect, and a strong impression of “clarity” and resolution/detail that’s evident even on first listening to the RDAC. There’s nothing artificial to this … the detail is real and
notof the often-encountered “artificial hyper-detail” found in many D/S type converters. Brushes on cymbals or drum skins, decaying triangle strikes, and so on exhibit are resolved to a level that I’ve generally only found on rather more expensive units.
Dynamics, both macro and micro, are addictive. “Sledgehammer” (Peter Gabriel) or the intro to “Twist in my Sobriety” (Tanita Tikaram), which are possibly opposite extremes, still both provide graphic illustrations of the ability of the RDAC to simultaneously handle large dynamics while maintaining deftness, subtely, and resolving power with micro-dynamics. Cohen’s typically gravelly delivery, perhaps exemplified in “You Want it Darker”, also serves as an excellent illustration of the Massdrop R-2R DAC’s ability to portray tiny, subtle, variations in volume modulation … which gives his voice a lot of its visceral emotion.
All of this is set against a deep, dark, velvety-black backdrop. There’s no sense of veil here. Clarity is excellent and, again, “pristine”. Noise on the recording, be it from the tape, the environment (in acoustic recordings), and so on will be fully reproduced, but nothing is getting added to it. I think this is, as with a couple of other DACs I’ve listened to recently, a major factor in how pronouncedly some of the other positive traits are rendered.
Technical Details
Inputs and Supported Formats/Resolutions
The RDAC offers three inputs - S/PDIF via COAX (RCA) and TOSlink, and USB via a micro USB socket. These are selectable, sequentially, via the “Input” button on the front of the unit.
The USB input
IS galvanically isolated, and the USB input
doesrequire USB host power to function as a result. As is typical for isolated USB interfaces, USB power drives the source connection side, and power from the DAC itself drives the DAC side of the USB interface. This also means the unit will show up on your computer even if it has not been powered on.
This isolation seems to be pretty effective as using the COAX or TOSlink inputs did not yield a useful, audible, difference in quality in my setup. Similarly, trying a variety of USB-to-USB “purifiers” and/or DDCs in the chain did not yield a conclusive improvement.
So, while you may experience different results, depending on your precise chain, the USB input is the way to go with this unit in my opinion. Though the option for TOSlink is particularly nice if you want to pair this with a TV/AVR/game console or are having issues with ground loops.
In general, though, to get the most out of the RDAC you’ll want to use the USB input. This will give you the broadest range of bit-rate and format support. Officially, USB will let you play PCM up to 24/384 kHz and double-rate DSD (DSD128). With S/PDIF and a native DSD stream you can get to DSD128 and 24/192 kHz for PCM. S/PDIF using DoP will limit you to DSD64 (single-rate).
Interestingly, and I’ll stress that this is NOT something that is officially supported, nor guaranteed to work, I’ve been able to run the unit at 24/768 kHz and DSD256 (quad-rate) without any issues at all via USB.
DSD Replay
As mentioned, the Massdrop x Airist Audio R-2R DAC is natively a multi-bit PCM converter. It can accept native DSD
inputas well as via DoP, but that DSD content will be converted to PCM before being fed to the actual DAC ladders.
Absent completely discrete PCM and DSD conversion stages, all DACs must do some kind of conversion from one of these formats to the other. For example, the PS Audio DirectStream models convert everything internally to DSD before doing anything else, whereas units like the RDAC or the Soekris units convert DSD to PCM.
What matters most, of course, is what the end result sounds like. Interestingly all of the positive traits I found in the unit are preserved with DSD source material – the same sense of clarity and “pristine” nature of the sound is fully in evidence, and the tone retains the hint of sweetness that I keep going on about.
In practice, this turns out to mean that the relative positioning of this unit vs. the others I compared it to, remains almost identical regardless of whether you’re feeding the RDAC PCM or DSD. I will say that the low-end of the iFi Micro iDSD Black Label cleans up a little when fed with native DSD content, but at best that brings it on par on that
oneaspect and overall, I still prefer the presentation from the Massdrop unit.
No Snap, Crackle nor Pop!
It is very common for DACs, even expensive ones, to exhibit nasty pops, clicks, and other noises when switching between DSD sample rates and between DSD and PCM content. So, it’s nice to find that the RDAC makes no utterances during such switches. The unit mutes momentarily during these changes. In general, this is transparent unless you’re skipping tracks. There was no intrusion into the replay of a normal playlist of mixed rate DSD and PCM files.
Power & Power Supplies
Power to the Massdrop x Airist Audio R-2R DAC is supplied via an external switching PSU rated for 3W @ 5v DC and uses a standard barrel connector. The external nature of the supply means that you can, if you are so inclined, substitute a suitably rated linear power supply instead. Note that all of the listening performed for the main part of this review was performed using the stock PSU.
Out of curiosity, once the main listening was done, I did try a couple of different LPS units here:
The Teddy Pardo “Teddy5/3” yielded a small reduction in the noise floor, a side effect of which meant very low-level detail was more easily discerned vs. the stock PSU. Though it’s worth bearing in mind that this particular PSU costs more than the RDAC itself, and the very minor change in performance probably isn’t worth it, nor is it likely to be
routinely audible.
The iFi Power, which is technically underrated for this application (2.5A instead of 3A), did
notseem to offer any
audibleimprovement at all. Though this is also an SMPS, just with more filtering and “active noise cancellation”.
And my lab-grade supply - which gave a larger improvement than the Teddy Pardo unit, but at an even more ludicrous value proposition (several times the price of the RDAC).
My recommendation is, worry about your headphone and amplifier first and when you eventually have nothing else to adjust,
maybe add an LPS to the RDAC!
Converter Technology
The Massdrop x Airist Audio R-2R DAC is a 24-bit discrete R-2R (multi-bit, resistor/string ladder) sign-magnitude, oversampling, converter, using low phase-noise NDK clocks and a custom linear phase filter.
That’s an impressive configuration for a DAC at this level, particularly the implementation of sign-magnitude conversion. This dramatically improves linearity vs. a simple ladder (as much as two orders of magnitude at -60 dB). In listening to other DACs using simple ladders vs. a sign-magnitude implementation it has been my consistent finding that a sign-magnitude approach yields clearly better results - even when compared to much more expensive units.
Sign-magnitude converters use two separate ladders per channel to improve conversion linearity. With a single ladder, any non-linearity in the ladder winds up being relative to the full-scale signal. A simple R-2R ladder specified with 0.001% distortion actually has increasing distortion in inverse proportion to the signal level, reaching 1% by -60 dB. With a sign-magnitude implementation, as used in the RDAC, the specified distortion remains constant … so 0.01% at 0 dB stays 0.01% at -60 dB.
Comparisons to Other DACS
Schiit Modi MB (via USB) - $250
For a long time, my go-to reference for an “entry level” DAC has been Schiit’s Modi MB. I still think that it is an excellent unit. The RDAC offers a sweeter presentation, better resolution and clarity and a darker background compared to the baby-Schiit. The difference is enough that I think the RDAC is the better buy, despite it’s $100 higher price-point - if you can swing it, you should in my opinion. The Modi MB does offer a slightly more impactful bottom end, but the difference isn’t huge and is likely affected to a much greater degree based on amplifier pairing.
Schiit Modi MB (w/ Eitr) - $379
Adding an Eitr in the replay chain ahead of the Modi MB and driving it via COAX brings things a bit closer together, however I would still place the RDAC ahead - particularly when it comes to clarity, resolution and top-end air/space.
Chord Mojo - $549
While the Mojo has a slightly warmer signature, the Massdrop unit exhibits better bass texture and weight/slam combined with a notably smoother higher treble rendering. Raw resolution is similar in the mid-range, but I prefer the tone of the RDAC. And the Arisit Audio DAC conveys a better sense of air and the general ambience of the venue with the acoustic recordings I tried.
Bifrost MB (w/ USB Gen 5) - $599
Next to Bifrost MB, the RDAC continues to deliver a blacker background, the sweeter presentation and there’s still a slight sense of better clarity out of the RDAC. But now resolution and micro-dynamics are largely on par and the Schiit DAC’s low-end drive is still slightly superior. Again, not a big difference, but absolute bass-heads might prefer the Schiit unit - depending on what amp they’re pairing with.
iFi Audio Micro iDSD Black Label - $599
Not a perfect comparison, as the Micro iDSD BL is not just a DAC and, as such, presents interesting variations in perceived value based on how it’s going to be used. AS a pure DAC, however, the smoothness of the Micro iDSD seemed to take a little of the edge off brass and discordant piano (that’s a negative, as far as I’m concerned) compared to the Massdrop DAC.
The mid-range delivery between these two units is similar in terms of liquidity and resolution, though the “sweeter” delivery from the R-DAC works better for me without coming across as specifically romantic.
Bass is rounder and fuller out of the iFi unit, but this came at the cost of a slight loss of texture into the mid-bass vs. the RDAC. I’d say
quantityfavors the Micro iDSD and
quality the RDAC.
DENAFRIPS Ares - $650
The Ares has slightly more weight in the bottom end than the RDAC, though perhaps not quite the Massdrop unit’s dexterity with a fast, multi-tracked bass line. Mid-range lacks the sweetness of the RDAC, which may or may not be a good thing for everyone. Transient response, particularly with plucked-strings and rapid percussion, favors the RDAC - as do both macro and micro-dynamics and raw resolution.
Other Comparisons?
At this point, it would be fair to say that I’m rather surprised at how high up the DAC-price-ladder the comparisons to the RDAC have already gone, without finding a unit that clearly outperformed it both technically and in terms of overall listening enjoyment.
How high did I have to go to meet that target?
It wasn’t until I got to the level of the RME ADI-2 DAC and the Soekris dac1421, both coming in at around $1,000, that I could say that I found something that was, across the board, better technically than the RDAC while being as enjoyable to listen to (I do still like the hint of “sweetness” from the RDAC, however). You should also note that those units give a slightly false sense of the level of price/performance on offer here as they include other features, including capable headphone outputs and, with the RME unit, a very rich EQ and DSP capability.
Summary
The Massdrop x Airist Audio R-2R DAC is an
excellent sounding DAC, with a slightly sweet tone, a distinctly “pristine” and clear delivery and offering
very highvalue. In the month I’ve been listening to it, it has been unfailingly engaging and involving, while continuing to impress on technicalities.
For the $349.99 asking price, the RDAC is an easy and enthusiastic recommendation.
Compared to its primary competition, and some units that could reasonably, at least on a price basis, be considered one or two tiers above it, the RDAC offers both higher value and, for me, both better performance and a more enjoyable overall listen. As such I expect it’s going to prove to be somewhat disruptive in the sub-$800 DAC ($1,000 DAC/amp) market.
Some of that has to be attributable to the Massdrop design and manufacturing approach, which clearly enables higher than expected performance at lower than typical cost.
You can be sure that I’ll be joining the drop when it goes live on 6/6.