Channel Islands Audio Transient Mk.II & VDC•5 Mk.II USB D/A processor & power supply

March 7, 2014, 9:42 am

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Most folks don't even know they exist, but the Channel Islands are a chain of eight moderately sized mountains poking through the Pacific Ocean along the coast of southern California, between Santa Barbara and San Diego. The most famous of these is Catalina Island and its city, Avalon, which sit opposite San Clemente. The other Channel Islands are relatively wild and have been preserved mostly uninhabited.

On the mainland across from these isles, in Port Hueneme, is Channel Islands Audio (aka CIAudio), a company of modest size that's been around for 17 years and makes compact power amps, preamplifiers, and digital/analog converters. Like the islands, always sitting quietly off the coast but barely seen, CIAudio had always been in the periphery of my audio world, though I knew little about them. So I was pleased to get the Transient Mk.II USB DAC-preamp and optional VDC5 Mk.II power supply in my system, to learn firsthand what CIAudio is up to DACwise.

At 4.45" wide by 2.9" high by 5.25" deep, the Transient Mk.II ($699) fits into an open palm and is thus very portable, hence its name. The understated case, made of 1?8"-thick aluminum, is nicely finished, with a 3/16"-thick front panel. All hardware is nonmagnetic stainless steel, and the Transient feels solid and nonresonant.

On the front, starting at the left, is something I love to see on a DAC of any price: a row of six LEDs that indicate the incoming signal's sampling rate, in this case 44.1, 48, 88.2, 96, 176.4, and 192kHz. On the right are stacked two small buttons, with arrows to indicate volume up and down, and next to each of these is another LED. Each volume button's LED flashes as you tap it, then stays lit when you hit its limit. You can also use these buttons to set the DAC to Line Level, if you don't need the volume function.

On the rear panel, starting at the left, are the unbalanced left and right audio outputs (RCA). At the right top is the USB input, and below that the three digital outputs: a 75 ohm BNC connector galvanically isolated for S/PDIF (an RCA-to-BNC adapter is included), a mini-DIN jack for I²S, and an HDMI jack for differential I²S (also used by PS Audio, Wyred4Sound, and others).

With its variety of outputs and 24-bit volume control, the Transient can be used as a USB DAC, a DAC-preamp, or a USB-to-S/PDIF or USB-to-I²S converter. The only thing missing for a desktop system is a headphone jack.

Power that doesn't corrupt
There's one more thing on the Transient's rear panel: to the right of the digital outputs is a DC input, for the optional VDC5 Mk.II power supply. Although the Transient was designed to be powered by the 5V available from a computer's USB output and still output a full 2V analog signal, and has onboard filtering to clean up that incoming power, CIAudio suggests that if you want the best sound, hook it up to the VDC5 Mk.II. Housed in a case identical to the Transient's, the VDC5 costs $329, bringing the total package price to $1028. The VDC5 is marketed to also replace the power supply that comes with the Squeezebox Touch music server.

CIAudio points out that the quality of DC provided by USB varies quite a bit from computer to computer, and can often contain noise, ripple, or simply not enough current, all of which can affect sound quality. The VDC5 Mk.II's regulated linear power supply is designed to feed the Transient pure high-current (2.5 amperes) DC with no noise or ripple.

The VDC5's front panel has only a single power-indicator LED; on the rear are a power switch, an IEC power socket, and a 5V output jack. A short cable is included to connect it to the Transient, the two models together forming a matched set. Both are "handcrafted" in Ventura, California, and come with a five-year warranty on parts and labor.

The Transient's USB input connects to a four-layer custom USB board featuring an XMOS multicore processor and ultraprecise clocks, which CIAudio claims work with the computer to generate a low-jitter I²S signal. The precisely clocked I²S output is then fed to four circuits: a buffer for the I²S DIN output jack, a differential buffer for the HDMI I²S connector, an S/PDIF transmitter for BNC S/PDIF output (based on a Wolfson WM8805 chip), and into the onboard Wolfson DAC chip. Takman resistors and WIMA polypropylene capacitors are used for signal circuits.

CIAudio's Dusty Vawter emphasized to me in an e-mail that they wanted the Transient to be completely portable, which meant that it had to be able to be run from the 5V supply available from a laptop's USB port. "There are very few DAC [integrated circuits] with this capability," Vawter said. "We listened to offerings from ESS, TI, and Wolfson. In the end, we chose the Wolfson due to its superior musicality and benefit of having a built-in 24-bit volume control."

Set-Up
Connected to a LightningtoUSB Camera Adapter, the Transient didn't power up when connected to my iOS7 iPad Air, iPad mini, or iPhonenot surprising, considering how the DAC's design sucks up every bit of current it can get, and these battery-powered iDevices don't put out much via USB.

But I was surprised to find that, after powering the Transient with the VDC5 power supply, I still got a warning on the iDevice display that the power draw was too high. Interestingly, this time the warning notice mentioned the CIAudio DAC by name, so more info was getting through, but not enough to include music. Occasionally, the Transient's LEDs would blink. Only a handful of USB DACs have been able to work straight off my iPad, by the way, so this is not a really a criticism, just a note to those who might want to use the Transient this way. To fire it up with an iDevice, you could also try a powered USB hub.

However, when I attached the Transient to my MacBook Pro, everything powered up fine without the VDC5, and worked right awayno need to reboot or for extra drivers. The DAC also works with Linux and, like all high-resolution converters, requires download and installation of a driver for computers running Windows XP through Windows 8. All of my listening was done with the Transient connected to the battery-powered MacBook.

Music that might corrupt
In honor of the Channel Islands, I felt obligated to throw some California music at the Transient, beginning with the fabulous new 24-bit/192kHz remasterings of the Grateful Dead's studio albums, from HDtracks. These are remastering done to perfectioneven less-than-fanatical Deadheads should grab them.

I skipped around a couple albums, then settled down with American Beauty for some extended listening. Everything sounded in the right place, with a beautiful flow from top to bottom. I used the loose, open arrangement of "Sugar Magnolia" to check for any changes in the sound as I switched the external power supply on and off. (The Transient will automatically default to USB power if the VDC5 is switched off, and automatically default to the VDC5 when the latter is switched on.)

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ASUS Xonar Essence One Muses Edition D/A processor–headphone amplifier

March 7, 2014, 9:48 am

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Back in the summer of 2009, USB-connected D/A processors that could operate at sample rates greater than 48kHz were rare. Ayre Acoustics had just released its groundbreaking QB-9, one of the first DACs to use Gordon Rankin's Streamlength code for Texas Instruments' TAS1020 USB 1.1 receiver chip. Streamlength allowed the chip to operate in the sonically beneficial asynchronous mode, where the PC sourcing the audio data is slaved to the DAC. But high-performance, USB-connected DACs like the Ayre were also relatively expensive back then, so in the January 2010 issue of Stereophile I reviewed a pair of soundcards from major computer manufacturer ASUS , the Xonar Essence ST and STX, which, at $200, offered a much more cost-effective means of playing hi-rez files on a PC.

I was impressed by what I heard from these cards, and concluded in a Follow-Up that "the Xonar Essence STX and its PCI-bus equivalent, the Xonar Essence ST, can be recommended to those on restricted budgets who wish to incorporate a PC into their high-end rigs." So when ASUS announced that it was introducing a version of its standalone Xonar Essence One D/A headphone amplifier fitted with JRC's high-performance Muses op-amps, which I had first experienced when I reviewed the Esoteric D-07 D/A processor in January 2011, I asked for a review sample.

The Muses Edition
The Xonar Essence One is a hefty processor housed in an elegant, black-painted enclosure. The basic Essence One costs $599; the Muses Edition, which can be distinguished by the black color of the stylized lion graphic on the top of its extruded-aluminum sleeve, costs $899. On its front panel are, from left to right: a power button; buttons to select Upsampling, Input, and Mute (the selected input LED turns from blue to red when Mute is selected); a large volume control for the line outputs, to its right an arc of blue LEDs; a smaller volume control for the headphone output; and a single ¼" (6.3mm) stereo headphone jack. Because there are independent volume controls for the line and headphone outputs, the line output doesn't mute when headphones are plugged in. On the rear panel are pairs of RCA and XLR jacks for the single-ended and balanced line outputs, respectively, and input jacks for USB data and S/PDIF data on TosLink and coaxial links.

When the upsampling function is off, the sample rate of the incoming data44.1, 48, 88.2, 96, 176.4, or 192kHzis displayed by the arc of LEDs. When the upsampling button is pressed, data at 44.1kHz are upsampled to 352.8kHz; data at 48kHz and its multiples are upsampled to 384kHz. ASUS calls this "Symmetrical 8x upsampling," because the upsampled frequency is an integer multiple of the incoming rate. None of the LEDs illuminates when upsampling is engaged. However, there is an LED at the top of the arc labeled Bit Perfect; though this never lit up when I used the Xonar processor with my Mac mini or MacBook Pro, it is supposed to do so when the Essence One is connected to a Windows PC and the necessary ASIO driver (supplied on a CD-ROM) is installed. (I couldn't verify this, as all my auditioning and measuring was with Macs.)

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Inside the box, the circuitry is neatly laid out on a large printed circuit board, with a cutout in the board for the toroidal power transformer. S/PDIF data are routed to an AKM AK4113 receiver chip; USB data are handled by a C-Media CM6631 USB receiver (the same chip used in the Schiit Bifrost DAC reviewed by Jon Iverson in August 2013). The audio data are passed first to an Analog Devices SHARC ADSP-21261 40-bit floating-point DSP chip, then to a pair of TI's PCM1795 DAC chips.

The PCM1795 is a two-channel, 32-bitresolution device that is pin-for-pin compatible with the earlier and widely used PCM1792 chip; according to its datasheet, the PCM1795 is DSD-capable, but the Essence One will not decode DSD data. Also according to its datasheet, the PCM1795 is intended to operate up to a sample rate of 200kHz, so I'm not sure how ASUS is able to use it at 352.8 or 384kHz when upsampling is engaged. I wondered, as the chip is a two-channel part, each channel could be fed alternate samples, to give an effective doubling of the sample rate, as was once done by Stan Curtis in a mid-1980s Cambridge Audio CD player. However, my measurements (see Sidebar) suggest this isn't the case.

Unusually, all of the eight-pin op-amp chips, a mix of JRC and Muses devices, are socketed. The six Muses 01 dual op-amps, which follow the DAC chips, are made with advanced fabrication techniques said to reduce crosstalk and produce better-balanced left/right channel symmetry, and use oxygen-free copper leads. The headphone amplifier appears to be based on a pair of TI's LME49720 high-performance op-amp chips and an LME49600 high-current output driver; the line outputs appear to be based on TI's LM4562 ultra-low-distortion, low-noise, high-slew-rate op-amps. Other than the headphone output, all the analog audio circuitry is heavily bypassed with local electrolytic and plastic-film capacitors. Overall, the parts count and the quality of those parts are very high for a relatively inexpensive product.

Sound Quality
I used the Xonar Essence One Muses Edition for all my regular headphone listening during the fall of 2013, as well as during the preparation of my review of the Audeze LCD-X headphones elsewhere in this issue. I also used it in my big rig (see the "Associated Equipment" sidebar). Although the Xonar DAC had already been reviewed by Michael Lavorgna and Dinny FitzPatrick on, respectively, our sister websites AudioStream.com and InnerFidelity.com, I didn't read my colleagues' reviews until I had finished my own auditioning. But my impressions of the Xonar's sound quality to some extent echo theirs.

Used as a DAC without upsampling engaged, the Xonar Essence One didn't resolve recorded details as readily as the NAD M51 and Auralic Vega, though it's fair to note that those DACs cost very much more. There was a smooth, rounded-off quality to the Xonar's line outputs that was a benefit with typically overcooked rock recordings, such as the Pretenders'"Talk of the Town" and "Back on the Chain Gang," from The Singles (ALAC files from CD, Sire/WEA; and yes, I am rediscovering and relishing that delicious sob in Chrissie Hynde's voice).

But this character obscured the fact that my reissue of Richie Havens's 1969 album Richard P. Havens, 1983 (CD, Polydor 835 212-2) had apparently been mastered from an LP rather than from the original master tapes. And the dry acoustic of Yamaha's YASI recital hall in Attention Screen's "13 Trojans of Vundo," from their live recording Takes Flight at Yamaha (16/44.1 master file for CD, Stereophile STPH021-2), also seemed a little suppressed compared with the Auralic Vega's presentation. Chris Jones's fretless Fender Jazz bass guitar also sounded a touch softer, but the Essence One still revealed the hit in sound quality resulting from the lossy audio encoding in the video from the concert that I posted on YouTube, to which I had added the audio mix from the CD.

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