October 2016


Mytek Brooklyn DAC
Andrew 'Harry' Harrison gets to grips with the first non-Meridian MQA-ready DAC.
Review By Andrew Harrison

  DACs have actually changed little in the last 30 years. For sure, fidelity and linearity have improved, but the operation remains essentially the same. They still convert digital audio into analogue, and the core requirement is still focused on CD's 16-bit/44.1kHz PCM standard. Around 20 years ago the bit-depth and sample frequency capability of the best DACs increased to 24-bit/96kHz, aligning with the first high resolution digital audio recordings. But even after the launch of SACD's competing 1-bit DSD format, external consumer hi-fi DACs remained firmly in the familiar PCM world, thanks to Sony and Philips' success in excluding general access to the unencrypted DSD datastream. Only after SACD had effectively become obsolescent was 1-bit PDM digital put to good use in external DACs. The result today is that many consumer DACs made in the last five years now have bilingual fluency in both PCM and DSD formats.

Mytek's Brooklyn adds a third option. It's the first independent DAC to market that can handle a brand-new higher definition digital datastream devised by Meridian Audio, known as Master Quality Authenticated (MQA). Economical in information density for downloading and storage, it essentially promises the sound quality of 24/96. (see Colloms on MQA, HIFICRITIC Vol9 No1).

Hardware
The £1520 Brooklyn is a midrange product, in price at least, replacing the company's Stereo192-DSD. In a three-way test of DSD-capable DACs (HIFICRITIC Vol7, No3), the then £1,140 Stereo192-DSD was a Best Buy, leading this listener to purchase the product, and ultimately displaced my older dCS converters as the preferred digital reference. No surprise then that the announcement of a newer model with an improved specification drew my attention.

The Brooklyn comes similarly packaged in a half-width compact box, 1U in height, one of several clues to its pro-audio background. Changes include the latest converter chips, an ESS Sabre 9018K2M replacing the '9016, which sees a specified THD+N figure lowered from -110 to -120dB; this chip uses a proprietary 32-bit Hyperstream architecture which excels at DSD as well as PCM conversion, using a cascade of independent sigma-delta modulators with adjustable bit-width output (typically 6-bit).

The USB front end has been updated by a Class 2 USB 2.0 digital receiver. Windows users will still need to install dedicated drivers, but Linux and OS X computers now require no additions for operation up to a 384 kHz sampling capability. (A welcome situation since Mytek's development of the custom OS X driver for the Stereo192-DSD was abandoned last year, effectively marooning that product for Mac users.)

Gone, however, is the FireWire input, which proved the best-sounding option on the Stereo192-DSD. Mytek founder Michał Jurewicz agrees that FireWire is better suited to audio, but TC Technology discontinued the required DICE Mini 1394 receiver, leaving Mytek to focus on the USB input. While not fully galvanically isolated, ground planes are separated to reduced conducted noise. Traditional digital inputs comprise two S/PDIFs on RCA phono (configurable as SDIF for raw DSD); AES3 balanced digital; and Toslink as either S/PDIF or ADAT. A pair of RCA/phonos provide an equalized input, either for turntable cartridge or for line-level analogue sources. Word clock input and output are provided on BNC sockets, and analogue outputs are on XLR balanced and RCA single-ended sockets.

A stylish honeycomb pattern is etched into the surface of the front fascia, and the unit is available in silver or black finish. Two 0.25in headphone outputs can either power two pairs of headphones, or be combined to give balanced-mode drive for suitable 'phones via a double-jack-plug-to-XLR adapter.

A contentious revision may be the replacement of the internal linear supply by a switch-mode power supply. This provides the advantages of international voltage compatibility, reduced cost and higher efficiency, although audiophiles are rightly wary of such devices. Notwithstanding the module's perforated Faraday cage screening, these supplies are known to affect sensitive audio circuitry through radio-frequency switching noise. (Mytek has thoughtfully added an external power inlet on the rear panel, letting one use an external 12V linear supply instead.) While Mytek doesn't make such a unit itself, specialist suppliers have already accepted the challenge: Longdog Audio makes just such a power supply (£495, or £425 if bought with the DAC). This linear supply was tried on the Brooklyn, with beneficial results. Remote control is still possible via a supplied Apple IR handset.

The Brooklyn has a new multi-colour OLED display which provides detailed feedback on operations. The basic five-element peak level meters of the Stereo192-DSD are expanded to a 37-level bar graphic with numerical peak and average readings, that can help identify which recordings have been subject to loudness-war compression. Two alternative display modes include a simple screen showing volume setting, bit depth and sample frequency; and the full setup with adjustable parameters and the aforementioned meters. While the more intricate display is a marvel to navigate, its small fonts can now only be used up close, rather than viewed and adjusted from across the room. Ongoing firmware upgrades during the review period have already expanded the Brooklyn's feature set, adding absolute polarity and new mono modes; expect more improvements in future. Build quality remains excellent, though I did miss the precise action of the outgoing Stereo192-DSD's control knob, as the Brooklyn's knob has more play and less precise click detents.

MQA
As the first MQA-capable product outside Meridian, the Mytek Brooklyn is one of very few ways of hearing what the new format has been promising. Or, it could be said, will one day be able to, given the paucity of encoded music with which to try it currently. (Nearly two years on, only the Norwegian 2L label is actually selling MQA-encoded music.)

MQA was officially launched in December 2014. Rather more than just a digital codec, it's a complete end-to-end ecosystem for the distribution and playback of higher-resolution digital audio. Its inventors would rather dwell less on the digital technologies it employs as on the complete analogue-to-analogue signal chain from studio microphone to domestic amplifier (which just happens to include digital encoding, mostly lossless compression, digital distribution and then digital decoding along the way).

At its core MQA is still modeled on pulse-code modulation (PCM), but with surprising twists. An unpacked music file is specified in PCM terms of bit depth and sample frequency, typically sized as 24-bit/96kHz or 24/192; or based on CD baseband frequencies (hence 24/88.2, 24/176.4 and 24/352.8). Yet these hi-res recordings are packed and distributed in smaller packages that are recognised by legacy converters as either 24/48 or 24/44.1 files, with commensurately modest files sizes and streaming bitrates.

The Brooklyn accepts the still-packed datastream from a Mac or Windows PC over USB, then unfolds the buried data in a technique that creator Bob Stuart calls 'audio origami'. Interleaved throughout the digital data, a retrievable and reversible watermark is locked down by strong cryptography that requires embedded hardware keys to unlock, so only licensed decoder modules can access the full high-resolution content. The watermark includes song metadata, copyright and licensing information, and instructions on the required unwrapping and filter strategy for an MQA DAC. The listener needs only to know that a green 'authenticated' light shines. (An alternative blue light indicates that the encode is 'MQA Studio', meaning that the final rendition was signed-off by the original artist or producer.)

MQA also addresses an aspect of PCM technology that still troubles much of today's digital audio sampling – the meddling of both anti-alias and reconstruction filters. These typically introduce phase errors or ripples in impulse response (especially so in traditional 'brickwall' filters). MQA performs 'deblurring': erasing the fingerprint of the filters by using selected encode and decode filters which when combined produce more compact impulse response particularly in terms of the more troubling pre-ringing, which some contend relates to the hardening of piano timbres.

The Brooklyn's 'black-box' MQA module resides in an XMOS microcontroller on the main circuit board and can be enabled or disabled through the display interface. Three digital reconstruction filters are offered for general PCM playback – FR, SR and MPH. These signify fast and slow roll-off linear-phase FIR filters for general PCM, while the final minimum-phase filter is mandated for MQA playback.

Sound Quality
The well run-in unit's USB input was fed from an Apple Mac mini running Audirvana software to play the gamut of 16- and 24-bit PCM, DSD and MQA music files. The best results (in terms of a natural sound that was lowest in 'digital' colorations) used a CAD USB data cable, while the partnering system included Music First Passive TVC pre-amp and Chord SPM 1200C power amp driving B&W 802D speakers. Mytek DACs usefully include both analogue and digital volume controls (-99 to 0dB in 1dB steps). My preference is for the analogue version, but critical listening demands engaging the bypass mode.

My initial concern about the downgrade from FireWire to USB connection proved largely unfounded. Although the Stereo192-DSD-through-FireWire always sounded well-timed with precise, steady imaging, recourse to USB would somewhat Brooklyn's new crystal clock (named Femtoclock, but not from the IDT company which originated the name), or the updated UAC 2 USB receiver, I found that the new DAC provided the same level of structural solidity and focus, but that picture-painting detail was clearly improved overall.

Set against the far-from-opaque Stereo192-DSD, the Brooklyn managed to uncover rather more of the low-level detail that can draw one into a recording. This isn't highlighted detail from an upward tonal shift, so much as a wiping of the merest trace of mist from spectacle lenses. Returning to the Stereo192-DSD after trials of the Brooklyn, I found myself metaphorically leaning towards the speakers to catch what now seemed like missing musical detail.

The stock Brooklyn has a relatively dry sound, with a fractionally leaner and more even bass than its predecessor, but revelatory voicing brings the soundstage slightly closer. It does therefore miss out on the rounded and engaging bass quality that makes the Stereo192-DSD's bass lines more playful, revealing instead a faintly sterile attitude to the low notes. The top end sounds essentially sweet and vice-free, yet there is also some room for improvement, as I found when using an external power supply.

The external MCRU/Longdog linear supply enhanced timbral colour and wiped away some residual grain from an already clean-sounding DAC, and demonstrated clearer instrument separation. Initially I had reservations about speed and timing, as bass pace seemed to be slowed perceptibly, but this was remedied in turn by using an unfiltered mains connection rather than an Isotek Titan conditioner. Best performance was finally established by routing all the powered components through a Puritan PSM136 mains purifier, and now the Brooklyn fed by a linear PSU was in super-fi territory.

The balanced-mode headphone drive was a bonus. Using the adapter-plus-balanced-cable on Oppo PM-1 headphones gave palpably more grip and control, and improved dynamics created a more engaging sound. The limited selection of 20 tracks provided by MQA showed substantially lifelike transient details, as witnessed for example on the cymbal work of jazz piece Dark Dance by the Tomonao Hara Quartet.

However, the comparison could only be made between legacy playback (MQA disabled) for a 16/48-like version, and the full 24/192 unpacked file. Classical piano could sound outstanding from MQA material. A Chopin Prelude in B Minor was tripped of some honky-tonk clanginess that was evident in legacy mode, to reveal sonorous hearthrough notes decaying into a medium-sized room's clean acoustic space. The cherry-picked demo selection augers well for how MQA-treated hi-res recordings can sound, in the traditional audiophile sense. But some mainstream favourites will also be required in order to understand how well, for example, familiar rock, pop and jazz music times.

Playing with the three available PCM filter settings while switching between normal PCM and MQA tracks did however uncover a strong personal preference for the SR 'slow' filter on regular recordings. The minimum-phase filter could bring more clarity and precision to instrumental strands, tightening attack with cleaner incisiveness; this might all sound fine in quick-fire tests, but it also seemed to remove some of the sense of the musical flow. Rather like watching a movie where the audio leads the video by more than 50ms, it's still quite possible to watch and enjoy the film, but the slipped lipsync ultimately becomes wearing as the eye, ear and brain work to mesh the whole coherently within the head.

Set to MPH, top-to-bottom timing suffered, so recordings simply became less captivating. I found myself 'tuning out' music after a while as my attention wandered. The SR slow roll-off filter on the other hand gave the most relaxed sound for long-term listening prospects, front-to-back stereo imaging laid out in a more emphatic manner. And despite the potential for stop-band artefacts drifting down into the passband, I couldn't find any music that would introduce any distracting 'fizz' to the sound.

Conclusions
The Mytek Brooklyn is an outstanding D-to-A converter (DAC) on the basis of its CD-sourced PCM playback alone, never mind existing high-resolution PCM and DSD material. Given the double 'if' of whether MQA can prove musically engaging with conventionally sourced music, and if it does, whether the big three record companies will release their back catalogues this way, the Brooklyn will be well placed to unlock these files fully. And like the best electronic Lego, the addition of a linear power-supply is a doddle, with easy-to-enjoy musical dividends.

Company Information
Mytek Digital
Price: $1995
Website: www.MytekDigital.com