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Reviewer: Paul Candy
Source: Rotel RCD-971 as transport, Audio Zone DAC-1, CEC TL53Z CD Player [in for review], Pro-Ject RPM 5 turntable, Pro-Ject Speed Box, Ortofon Rondo Blue cartridge.
Preamp/Integrated: Manley Labs Shrimp, Blue Circle BmPH [in for review], Audiomat Opera Reference [in for review], Pro-Ject Tube Box phono stage.
Amp: Manley Labs Mahi monoblocks.
Speakers: Green Mountain Audio Callisto (on sand filled Skylan stands), (2) REL Q108 Mk II subwoofers, Green Mountain Audio Calypso [in for review], AV123 Strata Mini [in for review].
Cables: Various SilverFi interconnects and Sufi speaker cable, Acoustic Zen Silver Reference interconnects, JPS Labs Superconductor+ interconnects, Auditorium 23 speaker cable, Stereovox XV2 digital, Actinote cable loom [in for review].

Power Cords: Audience, GutWire, Harmonic Technology, DH Labs.
Stands: Grand Prix Audio Monaco four-tier rack.
Powerline conditioning: BPT Pure Power Center w/Wattgate 381 outlets, Bybee Quantum Purifiers and ERS cloth, GutWire MaxCon, Blue Circle BC6000 [in for review], Blue Circle BC86.
Sundry accessories: Grand Prix Audio APEX footers, Herbie's Way Excellent II Turntable Mat, Herbie's Black Hole CD Mat, Herbie's HAL-O tube dampers, Isoclean fuses, Walker Audio SST contact enhancer, Nanotech Intron 8500 CD fluid, Audio Magic/Quantum Physics Noise Disruptors, dedicated AC line with Wattgate 381 outlet, Echo Busters acoustic room treatments.
Room size: 11' x 18' x 8', long wall setup, hardwood floors with large area rug.
Review Component Retail: $2,680

Zero One Audio's Mercury CD/HD Player is essentially their Ti48 transport which John Potis reviewed in December 2005, paired with an onboard DAC. Thus far I have been disappointed with PC-based music systems both sonically and ergonomically. Even relatively inexpensive transport/DAC combos have performed at a higher level than any laptop-desktop-DAC combo I've tried yet. Hard drive or other magnetic-based music storage/playback may be the near future but it is still in its infancy and with plenty of unresolved issues as far as I'm concerned. Frankly, I'm not at all keen on navigating through Windows, MAC or any OS for that matter - plus tweaking settings and managing my music library. I absolutely loath the library features of both iTunes and Windows Media Player. My current music library management system works just fine. I don't need to worry about carpal tunnel syndrome either: I get up from the couch, walk over to my wall unit, pick out a CD or LP and drop it onto its respective player. That's it. Still, if someone could offer a hard-drive based system that outperforms most CD transport systems, without all the kludgy operating systems or the requirement for an add-on monitor, I might just alter my opinion. The Mercury is the first such product that seems to indicate a degree of maturity at hand. Let's find out more.

The Mercury arrived well packaged in a sturdy cardboard box. Upon receipt of a review product, I normally remove the cover and snap some pix. However, I couldn't remove this cover as a previous ham-fisted reviewer had stripped the screws. Therefore I had to settle for a photo emailed to me by Zero One's Alvin Heng.

According to Zero One's website, "The Mercury CD/HD Player combines the functions of the Ti48 CD/HD transport and an internal DAC based on the Ar38 design so that it will function as a standalone CD and hard-disk audio player. As with the Ti48, the Mercury has a software-enabled upsampling processor built-in that allows users to choose the sampling frequency and digital filter. The internal connection to the on-board DAC uses our custom I²S link and the sampling frequency can be set at various rates (e.g. 48kHz, 176.4kHz) up to a maximum of 192kHz. An S/PDIF (coaxial) output is also available and when using this connection to an external DAC, the Mercury can transfer data up to a maximum sampling rate of 24-bit/96kHz.

"The digital filter choices allow you to tailor the sound to your system or room to some degree. There are five filter options ranging from "no filter" to "brick wall". In addition, there are various dither options which help to optimize the performance of some DACs when the S/PDIF connection is used. The Mercury has 250GB of standard hard-disk capacity which enables it to save nearly 400 hours of uncompressed CD data. The Mercury can store either an entire CD or selected tracks. These can be organized according to artist or album name. Using these classifications, play lists can be created containing preferred tracks. The Mercury has a database that recognizes the album titles, track and artist names of nearly 2,000,000 CDs. This database can be easily updated with a CD-ROM (available from Zero One). The DAC section of the Mercury is based on the Ar38's DAC design, with multi-bit DAC architecture, fully regulated power supplies and a single-ended, zero feedback, discrete (no opamps in the signal path) output stage."

The terms upsampling and oversampling are the source of much debate and confusion in audio circles. The fact that several manufacturers either inadvertently or deliberately obfuscate the definitions only muddies the water further. Zero One's explanation is blessedly straight-forward:

"Upsampling and oversampling are forms of sample rate conversion (SRC), where one sampling rate (like the 44.1kHz of CD) is converted to another. With oversampling, the source rate is stretched out to an integer multiple (e.g. 4 times to 176.4kHz) by mathematical interpolation. The term upsampling tends to be used when conversion of the audio data is to a non-integer multiple of the source rate (e.g. 96kHz). SRC produces more output than input bits so devices such as the Ti48 increase the bit depth of the data to improve the accuracy of the processing and output.

"Neither upsampling nor oversampling adds data that did not already exist on the CD being played back. The benefits of the process mainly result from pushing the digital images that arise as part of all digital sampling processes further away from the audio band. With a sampling frequency of 44.1kHz, digital images of the data would appear directly after the valid audio data (at 22.05kHz). A very steep filter (commonly referred to as a "brick wall") would be required to remove the ultrasonic mirror images perfectly but the ringing that such filters introduce may affect the sound quality.

"By upsampling to for example 176.4kHz, the digital images of the data would be pushed out beyond 88.2kHz, allowing the use of a digital filter with a gentler slope to reduce the ringing and phase changes. Another possible benefit of having less steep digital filters is that these filters allow some ultrasonic noise to reach the D-to-A conversion chips. The ultrasonic noise may be acting as dither which would help to optimize the performance of the chips."

If the above wasn't sufficient enough, Zero One Audio's Alvin Heng emailed me a terrific technical overview of the Mercury. I wish every manufacturer was this forthcoming:

"1) Transport Section
This is based on the same (6moons) award-winning design as the Ti48 CD/HD Transport. It is a PC at heart running on Linux, with a custom user interface and our own digital processing software suite. It has been mentioned before in 6moons but may be worth repeating that our custom ripping software has been compared to the best currently known ripping software (Exact Audio Copy) and is as good as that and bit for bit accurate.

"The digital processing is done using software algorithms with 64-bit floating point maths so it is far more accurate than any off-the-shelf upsampling/oversampling or digital filter chip used in 99% of all CDPs. The digital audio then passes to the pro audio 24-bit sound card which is used purely to transfer the data via I²S to the internal DAC (there is no audio processing performed in the sound card).

"To ensure that the sound card is not the weak point, we feed it with a regulated, filtered DC supply. The card is also mounted on a separate isolator PCB which removes a significant amount of noise coming from the motherboard's electronics.

"2) DAC Section
This is a multi-bit design using the famous Burr Brown PCM1704 chip. There are no digital filters or upsampling chips on the DAC board. All the required digital filtering and upsampling is done in the transport section with our custom software. The digital audio is fed directly to the PCM1704 chips by internal I²S running at sampling rates of up to 24 bit/192kHz.

"The output section of the DAC is fully discrete, single-ended pure class A, with zero global feedback. What this mouthful means is no opamps or caps in the signal path and the design is as inherently linear as it can be without negative feedback. We like this approach because we feel that it maintains the harmonic richness of real music without any of the bleached, hyper accurate sound of some digital designs.

"3) Design Philosophy
We have had several customers compare the Ti48 and Ar38 to some very highly regarded, far more expensive CDPs or transport/DAC combos (often their own or belonging to friends) and all have said that the Zero One kit was either as good as or superior to these other makes. We think the reason is that we focus on achieving the playback qualities of musical fluidity and natural harmonic textures and tones. We don't worry too much about extreme treble or earth-shaking bass or soundstaging. It's not that our products are not accurate - we think they are true to the recording, just that nothing is emphasized over any other quality.

"Having achieved most of our goals with the Ti48 and Ar38 designs, we wanted to put them both into a single chassis which many of our customers had been asking for. But to get them to fit in one chassis, we had to throw out a few things. So some of the extensive internal shielding had to go and we had to cut back on some of the comprehensive supply regulation. We think the result is that the Mercury retains the most important aspects of the Ti48/Ar38 sound and cuts back slightly on the other more audiophile qualities.

"Lastly, and perhaps most importantly, we do not consider the Mercury to be an "audio server". We get lots of enquiries asking why the Ti48 or Mercury cannot be configured for multi-room and why they do not have modems to connect to the internet and why you can't rip to MP3 etc. The Mercury is a stereo, high performance CD audio player (just as the Ti48 is a stereo, high performance CD audio transport). To this end, we deliberately disabled the modem functions (to avoid viruses and electronic noise); we threw away the monitor (again, electronic noise); and we focused all the PC's processing power on just one thing: stereo sound quality (no glitches trying to stream to multiple locations). So sound quality was the key issue but you do get the bonus of having all your CDs in the hard drive."

As you can see, the Mercury is one brute of a CD player and occupies serious real estate on one's rack. It just barely fit on my Grand Prix Audio Monaco. The front panel is completely devoid of controls. You get a display and disc drawer - that's it. I'd have liked a few simple controls such as drawer open/close, play, pause, stop plus a button or two to scroll through the Mercury's various menu selections. You need the remote to access this machine which is why the Mercury ships with two in case you lose or break one. I won't tell you how many times I walked up to the Mercury to change a disc only to walk back to my seat to grab the remote - all the more reason to rip your CDs onto the Mercury's hard drive. I must admit, scrolling through various albums from my seat via remote was indeed handy. On the rear there are the usual RCA outputs, a digital out RCA, the IEC AC inlet and power on/off switch.

Specs are as follows:
- Reads CD, CD-R, CD-RW
- 250Gb hard disk drive ; higher capacity HDDs available on request
- Digital output : 1 S/PDIF coaxial (RCA)
- Analogue output : 2V RMS; 200 ohm impedance

- Remote control (no monitor or keyboard required for operation)

The comprehensive manual, in decent English, fully explained the myriad user settings such as choice of filter, word length, dither and sampling rate, as well as step-by-step instructions on ripping discs and managing the Mercury's music library. Zero One is careful about recommending any specific settings and is content with gently suggesting that users let their ears decide. The manual also points out that because some combinations are technically impossible -- i.e. upsampling to 192kHz without a digital filter -- various number crunching methods are utilized to output a signal. I quickly realized that the 192kHz sans filtering offered less than acceptable performance.

I experienced no serious operational issues with the Mercury. However, there were a few minor annoyances. The well illuminated and easily read display turned itself off 10 seconds after inputting a remote command. I would prefer the option of leaving it on. The plastic remote was relatively easy to master, with some extra buttons for a future preamp. However, it would have been nice to have a single button to directly access the various settings of the DAC rather than scroll through an on-screen menu - and a single button to open/close the disc drawer instead of two. Why have two buttons labeled open and close instead of a single button as just about every CD player on the market today sports? As with most cell phones, each key controls more than one letter for alpha-numerical inputs which can be a source of frustration for some. My Blackberry has a full QWERTY keyboard and is half the size of the Mercury's remote. Having said that, once I got to used to the remote, it was relatively simple to operate even when I had to manually input the artist name and album title of a disc that the Mercury's rather extensive database didn't recognize. I could direct-access my music library by tapping in the artist, composer or album title via the remote. It was not unlike accessing a contact on a cell phone.

Depending on your system configuration, you'll probably want to use shielded interconnects with the Mercury - its PC-based components tended to generate some RF noise. For this reason I couldn't use my favorite SilverFi Samarkand interconnect which picked up all sorts of beeps, chirps and clicks which were clearly audible from my listening area between tracks and during relatively quiet passages. As Alvin alluded to above, the Mercury does not contain the same degree of shielding and power supply regulation as Zero One's separate Ti48/Ar38 combo.

While the Mercury's rear cooling fan was quite loud while ripping discs, it quiets right down during playback and is essentially inaudible. I loaded up a few dozen discs during my time with the Mercury. Some recent favorites were Los Lobos' excellent The Town And The City [Hollywood 661] which is possibly their best album since Good Morning Aztlán; Elvis Costello's Delivery Man [Lost Highway 40011]; a fine recording of various Gershwin tunes [Harmonia Mundi HMU 807441]; Sir John Barbirolli with characteristically passionate performances of various chestnuts by Bax, Delius and Ireland [EMI 79984]; and a wonderful, both in sound and performance, jazz adaptation of Bach's Brandenburg Concertos by the Jacques Loussier Trio [Telarc 83644].

To say that playing tunes from the Mercury's hard drive was sonically superior to its CD transport is a gross understatement. The hard drive offered up far more low-level information and subtlety. I could hear far deeper into recordings and pull out all sorts of subtle strands of musical detail. There was also a beguiling degree of ease and naturalness that I almost never hear with any digital playback. Only CEC's belt drive players have competed in that regard.

If I seem a little evasive about the Mercury's sonics, it's because with the myriad of user-programmable features of the chip set available, it was difficult if not impossible to identify a consistent sonic portrait. You want a well-lit open soundstage with terrific depth and detail, set it to 24/192kHz sampling and one of the higher filter settings. You want a raunchy, vigorous rendition with the emphasis on dynamics and forward propulsion, flip to 16/44.1 sans filtering. Want to tame an overly bright recording? Try setting it at 24-bit/176kHz and -3dB signal attenuation and perhaps one of the other dither settings. The features that exhibited the greatest influence on sonics were sample rate and filter settings. I struggled to hear any difference between 16 and 24-bit word lengths. Maybe there was a difference but it was neigh impossible to confirm that in quick A/B comparisons. The dither settings were also difficult to quantify but useful with some recordings. My overall preferred setting was 24/176kHz, purist filter without any dither. I also quite enjoyed 16-bit/44kHz sans filter.

Even with the plethora of settings, I did observe some consistent sonics, however. The overall presentation regardless of settings was cohesive, clean, open, transparent and focused yet also relaxed, fatigue-free with exceptional depth, weight, inner detail and nuance. Beats and rhythms were spot on and I didn't observe anything that impeded the natural forward flow of music. The Mercury was one of the most impressive digital playback pieces I've ever reviewed. To date the only digital playback I've had in my home that I consider superior is Audiomat's Tempo 2.5 DAC paired with CEC's new TL53Z belt-drive player. This pairing is tonally fuller, more dynamic and organic, with excellent PRaT. But at nearly three times the price of the Mercury, it damn well better should be. Incidentally, both the Tempo and Mercury sport Burr-Brown's PCM1704 chipset which in my opinion was one of the best-sounding chips. It was also Burr-Brown's last multi-bit chip before they switched to delta-sigma designs which some folks claim don't sound as good. I have yet to hear a DAC or CD player I didn't like that featured the PCM1704, PCM63 or even venerable TDA1543. Many delta-sigma equipped players sound tipped up and slightly off in tonality, forward propulsion, PRaT or whatever you want to call the rhythmic/timing domain. To these ears, nothing drives a tune along like a good-old multi-bit DAC. It's interesting that many new chips utilize a hybrid delta-sigma/multi-bit architecture.

The Mercury was also superb as a transport via its hard drive and even beat the belt-drive CEC TL53Z when I used both as transports with my Peter Daniel designed Audio Zone DAC-1. Backgrounds were quieter with more apparent detail. However, the CEC came quite close - but I'll have more to say on that fine player as well as Audiomat's Tempo in a future review. If you're thinking of using the Mercury as a standalone transpor onlyt, I'd recommend the Ti48 instead with its superior shielding and power supply regulation.

In conclusion and minor foibles aside, I was impressed with the Mercury. It is the first hard drive-based playback component that I can heartily recommend and wouldn't mind owning myself. I could obtain whatever presentation I wanted via the plethora of playback settings and managing my software library was indeed a breeze. While I admire Zero One Audio's approach, my crystal ball indicates that they might want to consider adding a wireless and/or hardwire network link. While CDs will be around for some time yet, the future of music distribution is surely via the internet, hopefully DRM free with a choice formats including high-rez 24/192. In my
perfect little audio-nerd world, I could download an album onto my computer along with liner notes, photos and other additional content, send the recording to a unit like the Mercury via wireless or cable, then disable the link for maximum sonics and either read the liner notes on my laptop or print out a hard copy. That way I can keep the computer hardware away from my music system and maintain the user flexibility and superior playback sonics of hard drives. It is a dream I nurture e but alas, based on the recording industry's activities of late, I'm not holding my breath for high-rez downloads.

Quality of packing: Double boxed heavy cardboard.
Reusability of packing: Excellent.
Ease of unpacking/repacking: Very easy.
Condition of component received: Casing screws were stripped by previous reviewer.
Completeness of delivery: Perfect.
Website comments: Site is informative with decent quality pictures and pricing info.
Warranty: One year parts and labor plus 30-day money back home trial depending on location.
Human interactions: Always quick, professional and helpful.
Pricing: Exceptional value considering sound quality and user flexibility.
Final comments & suggestions: None beside what I noted in the review.
Manufacturer's website