Media Server Reviews

Perhaps because I grew up in post-WWII England, with austerity and food rationing the norm, I learned at an early age the value of frugality. It was a financial stretch for me to buy, in the late 1960s, my first real audio system: Garrard SP25 turntable with Audio-Technica cartridge, Kenwood integrated amplifier, Wharfedale Super Linton speakers. Even when I could afford to upgrade the system, other than replacing the Garrard with a Thorens TD 150 and the Audio-Technica with a Shure, I went the DIY route. Back then, in the early '70s, I assumed that the advent of op-amp chips like the Fairchild Semiconductor µA741 would make it possible for me to design and make, for example, a good-sounding preamplifier for a lot less than it cost to buy one from an established manufacturer. That assumption turned out to be wrong, of course, but frugality was, by then, a habit: too ingrained for me to shake entirely.

And I still haven't. When, at the end of the last century, playback of digital audio files became domestically feasible, it never crossed my mind that I should explore expensive dedicated hardware. The frugal route would be for me to repurpose something I already owned: my bargain-basement, no-name Pentium PC.

As I wrote in my review of the AudioQuest JitterBug USB noise filter in the September issue: In 2006 that PC had been replaced by an inexpensive G4 Mac mini, which I could use with a keyboard, mouse, and display I already owned—frugality incarnate! In 2012, the G4 Mac mini was itself replaced by a Mac mini fitted with a 2.7GHz Intel i7 processor and 8GB of RAM. Similarly, the file-playing software progressed from WinAmp (free) to iTunes (free) to the affordable Pure Music and Audirvana apps.

Then, as also mentioned last month, my 2012 Mac mini died.

Enter the Antipodes DX Reference
Perhaps it wasn't a cosmic coincidence that, just before the Mac mini's iDeath—both its logic board and power supply were fried—Stereophile had been offered for review a sample of a dedicated music player, the Antipodes DX Reference. Antipodes Audio, a New Zealand-based company that's new both to me and to the US, makes a range of music players; the DX Reference, their top model, costs $6500 with 1TB internal solid-state storage, or $7500 with 2TB. (I was sent a sample with a non-standard 2.7TB.) Also available is the Antipodes DV Zero, intended for use with NAS drives—it is a server without internal storage—for $5000. At prices such as these, the products of Antipodes Audio are about as far as it is possible to get from my frugal devotion to general-purpose computers.

But the DX is still a computer, albeit a very specialized and special one.

One thing to rule over them
Using a general-purpose computer to play audio files should work—but, in practice, the computer must fit its audio-file-serving duties into all the other things it has to do. (Windows users: Open the Task Manager app and check just how many processes are running even when your PC apparently has nothing to do.) By contrast, the Antipodes machine does just one thing: It retrieves audio files from its own storage or from network-attached storage (NAS), and feeds the data to its two USB 2.0 ports. (There is also a 3.5mm jack sourcing both a stereo analog signal and an optical S/PDIF datastream, as well as another USB port for plugging in a removable drive for backup.)

There are no peripherals: just a slot-loading DVD/CD drive to rips discs, and an RJ45 Ethernet port to permit control via another computer on the network, or via WiFi using an iOS or Android device. Using the Linux operating system, the Antipodes DX runs just two apps: VortexBox for setup, control, and disc ripping (see ); and, to manage the music library, Logitech's Squeezebox Server (formerly the Slim Devices SlimServer, SqueezeCenter, and Squeezebox Server; it supports gapless playback). The Antipodes server supports a wide range of audio-file formats: WAV, AIFF, FLAC, ALAC, AAC, M4A, MP3, Ogg, DSF, and DFF. PCM-format resolution can be up to 32 bits, with sample rates up to 384kHz. DSD64 and DSD128 files can be played.

The heart of the DX is a motherboard featuring a quad-core Intel Atom processor and 4GB of DDR3 RAM, the latter to cache the selected playlist for direct playback. According to Antipodes' founder, Mark Jenkins, the transfer from long-term storage to RAM is managed "in a better and more consistent way, which does improve sound. Exactly how the files are placed into RAM and read out of RAM to the audio output is very important to the sound quality."

The DX's internal storage comprises Samsung solid-state drives (SSDs) with 3D V-NAND technology. However, Jenkins elaborates that Antipodes is always testing new drives as they enter the market. "Each server is tuned to work with the particular drives used," he adds, "as each can generate a slightly different noise spectrum."

Jenkins clarified this statement in a recent e-mail:

"Accepted digital theory suggests that regenerating the signal in the DAC should cure all prior interference with the digital signal. But...as with all other areas of audio, it turns out everything matters in computer audio too. One area that appears to matter a lot is what happens in the server's RAM. For example, we find [that] an uncompressed FLAC file sounds a lot better than a compressed FLAC file, and the only thing that is different is that, with the latter, the file has to be decompressed in RAM (becoming identical to the former file) before the next step. Just that little bit of extra activity in RAM is enough to make a significant difference (as we have demonstrated in public blind tests).

"When we mount external storage, at a certain level of abstraction, it is being treated in the same way as playback from internal storage. That is, the file is requested by the server software and then transferred in block mode into RAM.

"Files stored internally flow over a SATA interface, and externally mounted files flow over Ethernet. The way we manage music files from internal storage in and out of RAM has turned out to be very important to the sound, and we can [get close to] this when we use mounted external storage over Ethernet. But UPnP/DLNA is different again. Just because it also comes over Ethernet, it does not mean the file arrives in the same way.

"For a start, we are less able to manage the process the way we would like and the stack is more complex. Amongst other things, UPnP/DLNA is designed to traverse a range of situations (such as playback of files that are too large to fit in the RAM of the DLNA Renderer) and so has high overhead with a lot of request and response activity...More activity is always a bad thing, and worse when it directly impacts the playback software stack.

"When Ethernet is involved (whether mounting or using UPnP/DLNA), we hear less immediacy, and a softened vagueness to images. Some people may actually prefer this by the way, calling the sound more romantic or less aggressive. System context is, as always, important. The simple point is that while mounting over Ethernet suffers a little from this, when using UPnP/DLNA (and internet streaming) this effect is several times greater...

"The best sound comes from the DX using internal storage. Second best is the DV Zero playing from a NAS; third best is the DX playing from a NAS; fourth best is the DV playing from internal storage (using our custom HDDs); fifth best is the DV (with internal HDDs) playing from a NAS. And by the way, if we add a small SSD to the DV to hold the playlist we get slightly worse sound."

Physical plant
Inside the DX Reference's polished aluminum box, behind the right-hand side of the machined front panel, is a large toroidal transformer; behind it is a linear (as contrasted with switch-mode) power supply. The disc transport is at the center, and behind it and to the left is the processor motherboard. A small board from the computer-audio specialty firm SOtM, above and to the left of the motherboard, handles IO duties. The only controls are a blue illuminated button on the front panel to toggle the DX between standby and on, and a rear-panel on/off switch.

Setup...
...was trivially easy. I used an AudioQuest Vodka Ethernet cable to connect the DX Reference to my WiFi router, and an AudioQuest Coffee USB cable to link the DX to either my PS Audio PerfectWave DirectStream D/A processor or Bel Canto Design's Black ASC1 preamplifier, and turned the DX on with its rear-panel switch. From cold, the DX took about three minutes to boot up, after which it appeared as a shared device on the computers on my network. I accessed its webpage with the browser on my repaired Mac mini (the address is http://antipodes1.local/), and the VortexBox setup screen appeared. The Configure Player screen then let me define the PS Audio and Bel Canto as two of the five allowable outputs, and I was in business.