mobanmarketWhen I survey the realms of fancy-pants audio, the first thing I notice are cohorts of luxury-brand manufacturers selling pride of ownership with emblematic faceplates. After that, I spot another type of manufacturer, one that mocks the first type and aims its products at a younger, more working-class demographic, seducing potential customers with how much “truth” they are offering for only $15. But sometimes, when I look beyond the full-page ads and big rooms at audio shows, I discover a rogue manufacturer that is peddling a very specific type of listening experience, which they believe is the best. A listening experience only they could have created. I am grateful for manufacturers like this. They make my job more interesting, and I admire them for their courage in betting on their own taste in music reproduction.
I am relating these observations because this month I’m reviewing a digital converter from an off-the-paved-road audio manufacturer named Benjamin Zwickel. He operates a company called Mojo Audio, which is located in Albuquerque, New Mexico. When Editor Jim Austin asked if I was interested in reviewing Mojo Audio’s Mystique X SE DAC, I told him I had never heard of Mojo Audio, but that I would check out their website. Halfway through the first website page, I realized Mr. Zwickel was one of those too-rare manufacturers with a strong viewpoint, one that inspires him to create products designed with a specific type of listening experience in mind. Zwickel explores an engineering strategy he believes is truer than others to the data in our digital files.
His well-stated beliefs reeled me in with surprising ease. I told Jim I was curious to see how Zwickel’s “unusual” approach to DAC design would work in my outlier sound system.
The Mojo’s mystique
Mojo Audio’s $9999 Mystique X SE digital-to-analog converter is an evolution of the company’s earlier series of DACs, the EVO series. Like those earlier DACs, the Mystique is what Zwickel describes as “purist design” because it only processes PCM—no DSD or MQA—and only does D/A conversion. According to the Mojo website, the Mystique X features an R-2R circuit that uses a pair of 20-bit Analog Devices AD1862 ladder DAC chips. “There is no pre-digital filtering, digital noise shaping, upsampling, oversampling, or error correction. Your DAC will decode up to 24/192 but will truncate 24 to 20-bit.” (footnote 1) The SE version of the Mystique X employs a “massive” power supply that uses Lundahl amorphous-core chokes (one for + and one for –) feeding five independent secondary voltages, one for each stage in the DAC circuit. Additionally, nine ultralow-noise, ultrahigh-dynamics Belleson SPX discrete regulators are used to isolate power to the clock, DAC chips, and the Staccato op-amps used for its direct-coupled analog output.
After unpacking the $9999 Mystique X SE, I held its 19lb, 9″ W × 4″ H × 16″ D extruded aluminum chassis on my lap, turning it around, absorbing its dark minimalist aesthetic. It looked like the DAC I’d been wishing for: a simple heavy box I can just plug in and forget about. No brightly lit display. No menu. No setup. No app for my iPad. No software updates. No plastic remote. No PCM filter choices. No external clocks. No DDCs. And! Only three digital inputs: a galvanically isolated asynchronous XMOS-compatible USB-B, AES3, and coaxial (S/PDIF). And two analog outputs: single-ended (RCA) and balanced (XLR). Also on the Mystique’s back panel, beside the mains power switch and IEC socket, there is a sliding DC ground-lift switch.
The Mojo’s distinctively styled black front panel looks artfully rugged with its baked-polymer finish and engraved insignia. Above the faceplate-filling “Mystique X” lettering sits three barely noticeable little buttons, each with its own tiny blue LEDs, used to select one of the DAC’s three digital inputs. A fourth, red LED above these indicates S/PDIF or AES3 input errors.
A few days after I received the Mystique X SE DAC, Mr. Zwickel sent me an email with a link to his blog and a pdf of a lecture he gave at AXPONA 2022 entitled “The Seven Myths of Digital Audio Dispelled.” (footnote 2) In that email, Zwickel also gave me what he called a “small glimpse” into the design strategies employed in the SE version of the Mystique X DAC I was reviewing.
“What makes Mojo Audio DACs so unique is this: We use the best of 100-year-old, 40-year-old, and modern technologies. The power supplies we use are LC choke-input, the largest, heaviest, most expensive, and least efficient type of power supply possible. It was well known over 100 years ago that this was the best power supply, the only type of power supply to provide instantaneous current, and the only type of power supply to be able to yield correct time and tune of music. Any other power supply typology is engineered to lower cost, reduce size and weight, and increase efficiency. Not to improve performance.
“As for the 40-year-old technology, that would be the vintage R-2R DAC chips we use. We’re far from the only company who is using these vintage chips, but don’t mistake true R-2R for the modern discrete-segmented R-2R.” Here, Zwickel named several well-respected DAC manufacturers (footnote 3). “They use multiple 8-bit discrete R-2R ladders and then use a FPGA to weigh and combine the ladders to achieve higher bit depths and better linearity. Sort of like a combination of true R-2R and Delta-Sigma technologies. And that is what they sound like: a cross between true R-2R and Delta-Sigma.
“As far as modern technology, we search the world for the best in modules and components, such as Vishay’s best TX2575 ‘Nude’ resistors, SiC Silicon Carbide zero-recovery Schottky diodes, Belleson discrete regulators, and JL Sounds XMOS USB input modules. Our chassis may look like a simple black box but it is anything but. Aside from the massive aluminum construction, we use a baked-on polymerized finish, which lowers mechanical resonance by about 11% over the anodized finishes most companies use, as well as improving durability. We use an Alodine undercoating, which lowers RFI and improves finish cohesion even more. We use all nonmagnetic, non-rusting stainless steel hardware.”
Zwickel concluded, “The most important thing is to be open minded and to always evaluate components in the system they will be played in using the digital source and software that will be feeding it. … Do some blind A/B comparisons with friends, where the listener does not know what they are hearing.”
The $9999 “SE” version of the standard $7999 Mystique X adds ultrafast, ultralow-noise, zero-recovery SiC Schottky rectification diodes and ups the capacitance of the four-pole Mundorf capacitors to 22,000µF; it also adds Lundahl amorphous-core input transformers on the S/PDIF and AES3 inputs.
Mojo sells its products direct to the end user and offers a 45-day, no-risk audition and a five-year transferrable warranty.
Footnote 1: See mojo-audio.com/blog/the-24bit-delusion/. I think what Zwickel is referring to is that regardless of the number of bits in the signal path, the real-world “resolution” of the very best DACs is in the 20-bit range. JA’s measurements have found that a few do slightly better (and some do considerably worse; see JA’s measurements in this review), but 21 bits seems to be the current upper limit. That’s a real-world limitation that’s difficult to overcome—and maybe pointless, since, as Zwickel also notes in that essay, when you consider not just the whole signal path but also the listening room, the true noisefloor is much higher. The only DAC I recall that Stereophile has reviewed that intentionally truncates to 20 bits is the Schiit Yggdrasil—thanks to Technical Editor John Atkinson for reminding me of that. I’m aware of a few others that use vintage chips and so truncate the datastream to 16 bits.—Jim Austin
Footnote 2: See mojo-audio.com/blog/7-myths-of-digital-audio-dispelled.
Footnote 3: We decided not to list the companies Zwickel named because they will not have an opportunity to respond. Still, I respect his opinionated candor.—Jim Austin
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