Technically sophisticated, ambitiously specified and with comprehensive connectivity, does Unison Research’s latest digital front-end deliver on its substantial promise?
It’s no longer contentious to suggest that the best days of CD are behind it. With sales in decline and the alternative means of content delivery gathering momentum, the number of affordable players on the market has already declined sharply, which is starting to affect price points further up the chain too. This said, there are vast numbers of CDs in circulation and the format still has many keen fans. And the CD player/DAC hybrid has become a popular addition to company ranges in recent years.
VALVE OR SOLID-STATE
The latest arrival in this category comes from Unison Research. The Italian company is perhaps best known for its extensive range of valve amplifiers but has had a considerable presence in the CD sector with its Unico range. The £3200 CDDue is its latest flagship model and, like earlier Unison Research designs, it has a valve stage supplemented here with the option of a solid-state output.
The DAC hardware of the CDDue is a departure from preceding Unison Research models, which have generally utilised Crystal or Wolfson chips. Developed in co-operation with the University of Padua, the CDDue uses an ESS Sabre ES9018 DAC, which confers compatibility with PCM at sample rates up to 384kHz/32-bit, and DSD to 4x (DSD256).
These can only be achieved via the USB-B port but the additional connections – single coaxial and AES/EBU sockets – are both good to 192kHz/24-bit and can additionally handle DSD64. A Toslink connection works up to 96kHz/24-bit while, by way of added convenience, a Bluetooth input supports A2DP v3.0.
The ESS DAC is joined by a pair of Analog Devices op-amps that act as current-to-voltage (I-to-V) converters. The valve complement is a quartet of 12AX7 triodes arranged in Unison’s differential ‘Totem Pole’ formation, claimed to combine low noise with a decently high output. As I’ve said, it’s possible to switch between this tube output stage and a solid-state buffer but, as PM’s Lab Report suggests, the latter offers a slightly lower overall output, potentially confusing any A/B listening comparisons.
As might be expected from a player at this price point, the CDDue has reasonable flexibility in terms of its set-up options. So balanced and unbalanced analogue outputs are fitted as well as coaxial, optical and AES/EBU digital outputs. The CDDue is additionally fitted with three digital filters, to allow you to fine tune your listening experience depending on your preferences and the material you happen to be listening to at the time. The absolute phase of the player’s output is also switchable and both this and the filters can be selected via the IR remote.
DSD, DRIVERS AND DISCS
While drivers need to be downloaded from Unison’s website to support USB audio with Windows’ OS (Win 7 and above are catered for), Apple OSX devices are a painless plug-and-play operation and the Unison also ran driverless from a Melco N1A media player used for listening. The driver was installed without incident on my Windows 7 laptop but as PM’s lab tests show, all is not completely well with the CDDue’s digital file handling. I was able to play files up to 96kHz/24-bit without incident but higher sample rates resulted in interference and dropouts over both USB and coaxial connections. To add to the mystery, however, DSD files were unaffected and played correctly over the USB connection.
Another rather unwelcome feature of our review sample was its tendency to produce an audible buzzing through the speakers for a few seconds after switching to a digital input from the player’s CD mode. Once this passed, the CDDue was appropriately silent via its digital inputs, although this was not always the case during CD replay.
The CDDue uses a KHM DVD mechanism running in CD-only mode and while the transport action is smooth and relatively quick to read the TOC, its mechanical action was audible with some discs during quiet passages from a distance of around two metres.
This mars what is otherwise a rather smart piece of industrial design. The CDDue is fairly large, but the simple front panel is elegant and well finished. Silver and black fascia options are available albeit with black commanding a £100 premium.
The 128x64mm display, in particular, is a well thought out feature as it conveys a fair amount of relevant information in a clear and logical way. There are some other nice touches: opening the CD drawer while playing a file via USB won’t automatically switch it to the ‘CD input’, for example. The remote also has plenty of useful functionality although the combination of wood and metal styling is a matter of personal taste and the hand it was moulded to fit is clearly a very different shape from mine.
UNFORCED ACCURACY
Initially connected to a Naim Supernait 2 amplifier and Neat Momentum 4i speakers, and with the valve output and digital Filter 1 selected, the CDDue made a compelling case for use as a premium CD player. Annie Lennox’s Diva [BMG Records PD 75326] demonstrated that there’s an unforced and compelling naturalness to how the Unison makes music.
In ‘Little Bird’, Lennox’s vocals were rendered accurately and distinctly with a beguiling richness and clarity. The presentation was spacious enough to render them distinct from the backing instruments but not so isolated as to be entirely divorced from them.
Its bass extension was also worthy of note. With Peter Gabriel’s So [Charisma PGCD 5], the way the CDDue reproduced the bass impact and undulating bass line of ‘This Is The Picture (Excellent Birds)’ seemed both forceful and well controlled. There wasn’t the sense of pace and urgency that you can get with some other players but the Unico CDDue does avoid sounding slow or muddled.
More than anything else, it’s easy to listen to for long periods, and my auditioning notes showed that I’d listened to rather more tracks on each album than I’d originally intended to.
Taking the same albums and listening to their ripped (FLAC) equivalents over USB via the Melco N1A, the CDDue proved utterly consistent in its performance, with the added bonus that the transport noise evident when spinning-up the Peter Gabriel CD was no longer a nuisance! Taking these music files and replaying them via the coaxial digital connection from a Naim ND5 XS also produced entirely consistent results. If you are thinking of connecting multiple devices to the CDDue, the signs are that it is admirably predictable across all input connections.
Where this consistency is less welcome is that for all the proclaimed adjustability of the CDDue, the performance of the player is barely altered by the three digital filter settings or, rather more surprisingly, via its solid-state output. Filter 2 imparted a little more treble energy to Leftfield’s Leftism [Columbia 01-478142-10] but no setting lifted the rendition of ‘Space Shanty’ to the point where it had the punch required to be truly compelling. The solid-state buffer has the slight but noticeable drop in output noted in PM’s Lab Report and though there’s a slight widening of the stereo soundstage and a lift to the midrange with it engaged, again, the effects are subtle at best.
Switching amplification to a Rega Osiris and changing to the balanced XLR connection placed slightly greater focus on this midrange emphasis and the top-end lift of Filter 2, but only marginally so. This need not matter unduly, for if you like what the Unison does, it will continue to please pretty much regardless of settings, but this is not the tweaker’s delight that its specs might suggest.
SHINES WITH DSD
The 96kHz/24-bit version of Paul Simons’ So Beautiful Or So What is refined, spacious and detailed but contrary to my usual experiences, a direct comparison here with the CD version [Hear Music 0888072328143] didn’t yield the same improvements in space and presence that I’ve experienced with other USB DACs.
Conversely, the performance of the CDDue with DSD material proved extremely good. With Ranagri’s Fort Of The Hare [DSD64; Stockfi sch-SFSA4085], the CDDue delivered a performance that was outstandingly refined and compellingly real. There was a sweetness to voices and instruments that builds on what the CDDue demonstrates with PCM. The presentation was detailed, spacious and impressively vibrant while simultaneously being free of any harshness or unwanted brightness. If you do have any meaningful quantity of DSD material, then the CDDue is a means of realising very good results.
Another area where the CDDue proves very capable is with material that’s been indifferently mastered or recorded. Unkle’s War Stories [SURR005CDXX] is a fine album but has a limited dynamic range and a somewhat aggressive presentation. The CDDue did a fine job of maintaining the attack and drama of the piece but added a civility to, for example, ‘Keys To The Kingdom’ that would be wholly beneficial to enjoying the album long term.
I should also mention the Bluetooth feature. Considering the player’s chassis is in metal and has no aerial, the connection proved stable and operated over a good range. It’s probably fair to say that enthusiasts spending £3200 on a CD player won’t be using it as their main listening source, yet it remains a useful convenience feature. Also, many of the positive performance attributes of the CDDue are present even with compressed material derived from the likes of Spotify.
VERDICT
The CDDue is a slightly frustrating product. Used to its strengths, this is an excellent CD spinner and player of 44.1/48kHz files, offering a satisfying and unforced presentation. The playback issues encountered with higher sampling rates, unwanted transport and USB noise and the slightly ad hoc nature of the filters all leave the feeling that the CDDue might benefit from a little more engineering TLC.
SPECIFICATIONS
Maximum output level (Balanced) 4.41Vrms at 22ohm
A-wtd S/N Ratio (CD / S/PDIF / USB) 114.6dB / 114.5dB / 113.9dB
Distortion (1kHz, 0dBFs/–30dBFs) 0.0006% / 0.003%
Distortion & Noise (20kHz, 0dBFs/–30dBFs) 0.008% / 0.003%
Freq. resp. (20Hz-20kHz/45kHz) +0.0dB to –0.26/–1.6dB
Digital jitter (CD / S/PDIF / USB) 117psec / 28psec / 33psec
Resolution @ –100dB (CD / S/PDIF / USB) ±0.3dB / ±0.1dB / ±0.2dB
Power consumption 20W (1W standby)
Dimensions (WHD) / Weight 450x130x380mm / 10kg