Massdrop x Airist Audio R-2R DAC

Featuring discrete resistor ladder technology at an unheard-of price, the Massdrop x Airist Audio R-2R DAC is one of our most requested and anticipated products this year: a DAC with the looks and quality to match our new lineup of amps. An older technology that’s been making a comeback, R-2R is known to produce rich, warm, natural sound and can have benefits in spatial awareness and staging. But because this type of design requires expensive high-precision matched resistors (and a lot of them), for a long time, well-implemented R-2R DACs could only be found in $5,000-plus products. More than 2 years in the making, this sign-magnitude DAC has two independent 24-bit ladders with 48 resistors apiece per each of the two channels, which cancel out errors and distortion for purer processing. It has a short, solid form factor and is designed to pair well with the Cavalli Tube Hybrid, Liquid Carbon X, and THX AAA™ 789.

Our goal was to make a DAC that does everything an audiophile would want a DAC to do: deliver accurate reproduction with resolution, attack and decay that sounds realistic, enough information to get a sense of space and instrumentation, and voicing that adds to the perception of true performance and enjoyment. We aimed to solve many of the common issues that can occur in DACs—namely, congestion, graininess, and the disjoined presentation of vocals to overall soundstage. Because digital storage and conversion are, at their core, math, errors or approaches can result in these unpleasant analog signal characteristics. For example, if unnaturally fast, sharp rise times are amplified from mathematical conversions, they can sound harsh or unnatural in your headphones or speakers. In contrast, this DAC maintains a consistent and natural soundstage, complex harmonics, clarity during busy passages, and an overall musical and resolving sound.

R-2R DACs are based on the fact that each bit of the binary sample represents a certain amount of voltage. Since each successive bit represents half the voltage of the previous bit, they use a resistor ladder to divide the reference voltage in half for each next bit. They need to use high-precision resistors to ensure that the division is as close to perfect as possible, and this is the main reason discrete R-2R DACs are so expensive.

Meanwhile, delta-sigma DACs avoid the need for precision resistors by changing the format of the signal. Rather than convert the full 16- or 24-bit sample, delta-sigma DACs convert the original digital signal into a representation with significantly reduced bit depth. Because these representations carry much less information than 16 or 24 bits, these DACs have to make up for this loss by increasing the sampling rate. Along the way, information is being lost and this creates some quantization noise. The core of a delta-sigma DAC is the delta-sigma algorithm, which reduces the effect of the added quantization noise.

Because they do not need the precision resistor ladder, delta-sigma DACs can be made at a much lower cost than R-2R DACs. They also require less power, and are better suited for portable systems than R-2R designs. However, because of the necessary noise-shaping filters in delta-sigma modulation, the analog output is somewhat removed from the digital input, and some feel this affects the character of the sound. On the other hand, the output of an R-2R DAC is exactly what the digital samples specify.

The RDAC contains two PCB boards: the bottom board with power, USB, and different file-conversion technologies, and the top board with the resistor ladders, designed to have the shortest distance between parts for the cleanest results. The hardware includes a custom programmable logic device and augmented power regulation with voltage-stabilization circuits. There is a buffer/isolator stage to each bit on the R-2R ladders, while the output buffer stage boasts five op-amps per channel. Finally, the inputs, outputs, and USB/SPDIF conversion are all located on a separate PCB from the resistor ladders. 

“Massdrop’s Airist R-2R DAC offers massive performance at a relatively low price ... It focuses on the fundamentals and makes beautiful, natural sound, much the same way my favorite vintage R-2R DACs did ... For offering a musically satisfying performance, with amazingly pure treble and accurate imaging, the Massdrop Airist R-2R DAC is a clear winner. Factor in the ability to upgrade it to an almost shockingly high level of performance, and you can see why it earns a very strong recommendation.” – John Grandberg on Head-Fi

“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 midrange 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 bassline and keeping vocals present and lucid.” – Torq on Head-Fi

“The RDAC has a nice, full, powerful low end with good extension. The midrange is liquid and free of congestion. The treble is on the softer side of things but has an effortless, clear quality to it, even if some of the overall details seem to not pop as much as they should. Unless you are opposed to this warmer tone and liquid but very slightly soft timbre, it should just flow with ease in listening. It also has a nice sense of swing and micro-dynamics to it. It’s nimble and grooves nicely despite its warmer, softer leanings. It’s never boring, veiled, or smothering.” – Hands on Super Best Audio Friends