Exogal Comet Digital-to-Analog Converter
by Vade Forrester
Digital-to-analog converters, a.k.a. DACs, continue to be one of the hottest-selling items in high-end audio, in no small part because of the increasingly widespread interest in playing music in the form of computer audio files. DACs range all over the price spectrum, from under $200 to (gasp!) $120,000 or more. Now, here’s another DAC from a new company, Exogal, which was formed in 2013 by folks formerly with Wadia. Wadia was purchased by Fine Sounds in 2011, a holding company. After the purchase, Wadia’s focus was redirected away from its former core competency of designing advanced transports and DACs. So it’s no surprise that some Wadia employees would want to continue working in the area where their passions lie. And in case you’re wondering what the heck an Exogal is, it’s a word created by combining “exo,” which means “out of,” with a shortened form of “galaxy” to denote it’s out of the galaxy. Now you know.
The first product Exogal has produced is the $2500 Comet DAC. The company offers a version with an upgraded power supply, the Comet Plus, at $3000. That puts it in the moderate price range, where it has lots of competition. So what distinguishes the Comet from other DACs in the same price range? According to Exogal CEO Jeff Haagenstad, “We had grown tired of watching the industry deliver more expensive products in more expensive cases that contained the same old tired 15-year-old technology. We didn’t want to buy that stuff at the prices our competitors were charging, and we thought others might feel that way, too. Good sound isn’t just for someone with more money than brains. We wanted to make great products that our children could afford and that delivered top-of-the-line audio performance, in a good-looking compact footprint that fits into their lives the way they want to live it. That’s why our products use smartphones as their primary remote control. Our kids are never separated from their phones! We also wanted to breathe some life back into a stodgy industry and prove that we could accomplish four goals: 1) to build great and affordable products; 2) that are profitable for a dealer to sell; 3) that are made in America; and 4) that we could pay our employees a decent wage for building. Maybe we can’t change the whole world, but maybe we can inspire people that the world can be changed, and they don’t have to accept it as it is. The founders of Exogal grew up when NASA was changing the world, and we wanted to do some of that in our own way.”
The Comet easily meets Exogal’s goal of being good-looking and compact. No one has ever accused me of having good taste, but to my eye the Comet is flaming gorgeous. Whereas some of its competitors produce DACs that are rather industrial looking (which should be no surprise—they are industrial-looking, since they were designed primarily for pro audio use), the Comet provides a high level of bling. I like bling; if I pay a high price for a piece of equipment, I want to feel pride when I show it off to others. And let’s not kid ourselves; though audiophiles may become jaded by the sky-high cost of state-of-the-art gear, for most folks $2500 is a high price. Once again illustrating that DACs don’t have to use full-size chassis, the Comet measures only 11.5" x 1.875" x 7.45". A small in-line power supply provides the juice.
Being an equipment junkie, I was curious to learn what was under the hood. What chips did the designers use? Haagenstad told me that “the Comet contains a TI PCM 4104 DAC chip for the main outputs, and a TI PCM 5122 DAC chip for the headphone output. I purposely used the word ‘contains’ because we don’t actually do a lot of ‘DAC-ing’ in these chips. We use them for final outputs but the actual ‘DAC-ing’ of the audio is done in a custom six-core DSP chip, which is all proprietary to Exogal.” This is a story that’s beginning to be more and more common: designers using innovative ways to push beyond standard off-the-shelf DAC chips to realize better sound.
The Comet’s curvaceous anodized aluminium sides and top are fastened onto an unusual base that looks like a slab of acrylic resting on four steel ball-bearings. I asked Haagenstad about the base, and he informed me that “not just the base but also the entire chassis is part of a constrained damping structure. We tried rubber feet, but they just didn’t give us what we wanted in vibration damping. I know: Go figure that rubber didn’t adequately damp the vibration, and that’s the reason. We scanned the chassis to find out where it resonated and the steel feet eliminated that last resonant frequency. Now it’s vibrationally as dead as a brick. Give it a rap with your knuckles and see.” I did and it was. Dead, I mean.
There’s a small display window (about an inch square) centered on the front of the Comet, which uses a non-illuminated LCD screen to show information about the outputs’ volume levels, the source selected, and muting status. I couldn’t read the LCD display unless I sat directly in front of it and shined a flashlight directly on the screen. I was puzzled: What’s the point of making a screen that’s so hard to read? And then there’s the remote control; it looks like something you’d hang on your car’s keychain, not a real high-end remote control. (I was afraid my cat would decide it was a toy, and it would disappear.) Then I learned the Comet is really intended to be operated remotely from an iPhone or iTouch. Android and iPad apps are coming, but in this case, there’s really not much information to display, so a smaller smartphone screen would work just as well as a tablet computer. As the smartphone apps provide all the visibility one needs, there’s really no need for an expensive screen on the Comet’s front panel. Still, would a larger, easier-to-read screen have been that much costlier?
The Comet plays PCM files with word lengths from 16 to 32 bits and sampling rates from 32kHz up to 384kHz and DSD64 and DSD128. The type of file and sampling rate are shown on the control app. The Comet is specified to operate with either Mac or Windows computers (the latter with a driver downloadable from the Exogal website), but when I tried it with the Linux-based Auralic Aries server/streamer, it worked just fine. The Exogal website has User Guides for the Comet and its SR-71 remote control device.
It’s becoming common for DACs to include circuitry that enables them to operate as the front end of simple systems, and the Comet does just that, functioning as a source selector and volume control. It’s ironic: Preamplifiers are starting to include DAC circuitry, and DACs are starting to include preamplifier circuitry. In addition to four digital inputs (AES/EBU on XLR, SPDIF on 75-ohm BNC and TosLink, and USB), the Comet has an analog input on isolated RCA jacks. The impedance of the analog input is only 1k ohm, which is extremely low; many source components may be incompatible with this impedance. For example, my Sony XDR-F1HD tuner, a relatively modern design, recommends a minimum load of 10k ohms. The Comet has a volume control, so it can drive a power amp directly via unbalanced (RCA) or balanced (XLR) outputs, or both. The output impedances of the RCA and XLR outputs are 9 ohms and 18 ohms, respectively, so the Comet should be able to drive any amplifier in existence. You can use both balanced and unbalanced outputs simultaneously, if you need to drive a power amplifier and subwoofers. Another I/O device on the rear channel is a short antenna, which sticks out the back about an inch, used to communicate with the iPhone (or whatever iDevice) that is acting as the remote control.
Of course, the Comet isn’t the whole solution to your hi-fi’s electronic needs; you’ll have to have a power amplifier to drive the speakers. Worry not. Exogal has a matching 125Wpc amplifier in development. The Ion power amplifier will only work with the Comet, since it uses its proprietary Exonet input connectors exclusively. Well, not exactly proprietary; Exonet connectors are HDMI connectors, and a standard HDMI cable is used to connect the Comet and Ion. Assuming HDMI cables can be made to sound good, it’s not really a bad idea to use them to connect components; you only have to fool with one cable per component, even for multichannel setups. (Home theaters have been using HDMI cables for years.)
Setup and Use
Of course, the first thing I did after unpacking the Comet was to read the User Guide. Isn’t that what everyone does? I had to download the 13-page document, along with a guide to the SR-71 remote control, from the Exogal website. Frankly, I found the user guide confusing. For example, it was not obvious to me that the preferred way of operating the Comet was via an app installed on an iPhone or iTouch. That’s pretty basic. Having an owner’s manual online is a good idea; hopefully, it will be updated to become more useful.
The small Comet, together with its power supply, took up about half a shelf on my equipment rack, so there was still enough room there for the Auralic Aries streamer and its power supply. I used a Paul Pang TZ YUN Red II USB cable to connect the Auralic Aries Wireless Streaming Bridge music player to the Comet’s USB input. Exogal recommends using the Comet to drive your power amplifier directly, so I connected the Comet to my power amplifier using Clarity Cables’ unbalanced Organic interconnects and to my subwoofer using CablePro Freedom interconnects. The Comet drove the amplifier and subwoofer with ample headroom. Although Exogal included a standard computer-grade power cord, I substituted a Clarity Cables Vortex power cord from the wall plug to the Comet’s power supply.
I installed the free Exo Remote app on my iPhone. Exo Remote showed me all the information on the Comet’s front-panel screen—except that on the iPhone I could actually read it. Exogal didn’t provide a recommended break-in time, so I gave the Comet 200 hours.
I tried the Comet’s headphone amplifier using HiFiMan HE-400 and Audeze LCD-X headphones—the least and most sensitive headphones in my collection, respectively. To get an acceptable volume level from the low-sensitivity HE-400s, I had to advance the Comet’s volume control to its maximum setting—and I’m no head-banger. The more sensitive LCD-Xs required a setting in the mid-80s—they’d be usable, but are still a little underpowered. Also, there was one significant feature missing from the Comet that’s been present in every headphone amplifier I’ve seen, and that’s a physical volume control. The notion of adjusting headphone volume with a remote control just seems weird to me—I want to reach out and touch some sort of volume control on my amplifier. But that’s a personal preference that you may not share. Additionally, I understand Exogal is planning to release a DAC with a higher-powered headphone amplifier soon.
The only gripe I had was that the Comet often produced a pop when an album started. I haven’t experienced this issue on most other DACs I’ve tried.
The Comet had an open, neutral, spacious sound with good bass and treble extension. Although there was plenty of high-frequency detail, I heard no peakiness or etch. Playing the Scherzo from Henry Litolff’s Concerto Symphonique No. 4, with piano solist Yuja Wang accompanied by the San Francisco Symphony led by Michael Tilson Thomas on the album Masterpieces in Miniature (DSD64/DSF, SFS Media/Downloads NOW!), I heard unusually explosive dynamics and excellent piano sound. Leading-edge transients were portrayed with greater than usual detail. The San Francisco Symphony was captured with particularly rich harmonics.
To assess performance with a male vocal recording, I queued up Neil Diamond’s recent album Melody Road (96/24 AIF, Capitol Records/HDtracks). The eponymously named first track found Diamond in excellent voice, captured by the Comet with rich, full harmonics. Microdynamics were depicted in detail, so that the song seemed to have lots of bounce and momentum. It’s good to have major artists continue to develop their craft instead of just repeating the songs of their heyday.
On the Tallis Scholars Allegri’s Miserere & Palestrina’s Missa Papae Marcelli (96/24 FLAC, Gimell), the track “Miserere” was unusually smooth, and the lead tenor’s voice was unusually expressive. The solo group, which sings some distance behind the main choral group, was very clear, and the Comet captured their distant location quite precisely, with none of the reverberant smear lesser components impose on the song. The distant solo group was reproduced with great purity, while the Comet portrayed the upfront choral group with no overload or congestion.
To assess how well the Comet handled female vocals, I played “Spanish Harlem” from Rebecca Pidgeon’s The Raven, (176.4/24 FLAC, Chesky/HDtracks, remastering by Bob Katz). The Comet captured the resonance of the upright bass that opens the piece with excellent accuracy, and it was easy to imagine Pidgeon vocalizing each word. All the instruments were portrayed with full, rich harmonics.
My reference system includes a PS Audio DirectStream DAC, which will directly drive one amplifier but not two, and I needed to drive both my David Berning ZH-230 power amp and my JL Audio fathom f110 subwoofer. So I had to interpose my Audio Research SP20 preamp between the DAC and the amplifiers to adequately source them. I moved the Paul Pang USB cable to the PS Audio DAC and connected the preamp to my speakers and subwoofer, using the same cables I had with the Comet to assure the only difference in the comparison was the DAC, the preamp, and the interconnect between them. The PS Audio DAC had the latest upgrade, the Pikes Peak OS. The cost of this equipment used for comparison was $5995 for the DAC, $9000 for the preamp, and $1400 for the Clarity Cables Organic interconnect cable, for a grand total of $16,395.
On Concerto Symphonique No. 4, the PS Audio DAC produced very detailed sound, with even more harmonic accuracy than the Comet. The overall transient envelope of the piano was quite realistic, with initial transient, sustain, and decay all sounding very lifelike. In other words, it sounded a lot like a piano, but played in a somewhat percussive style. As with the Comet, dynamics were explosive. The PS Audio DAC sounded exceptionally good to me, but the Comet came doggone close to matching its performance on this challenging piece.
On “Melody Road,” the PS Audio DAC had slightly deeper, more forceful bass, and exhibited even more detail in the instrumental accompaniment. Diamond’s voice exhibited superb nuance.
On “Miserere,” the tenor’s voice was even smoother and more detailed, his slight vibrato becoming more obvious. The distant solo group was reproduced with amazing detail, more realistically than I’ve heretofore heard it. I could hear the individual singers better than ever. The impression of the distant location of the solo group was just ideal, the epitome of how detail and reverberation should be rendered, with none of the smeared echo I once had mistaken for portrayal of depth. The PS Audio’s performance of “Miserere” was a benchmark for the piece.
“Spanish Harlem” was pretty close between the two DACs, but I thought the PS Audio DAC conveyed the resonance of Pidgeon’s voice slightly more realistically, and I could hear more texture in her voice.
Overall, I was surprised how close the Comet came to the performance of the PS Audio DAC/Audio Research preamp. The latter was a bit richer sounding, with more detail, and amazingly good bass response, but considering the reference gear was over 6½ times as expensive as the Comet, the Exogal was clearly a way better value. The Law of Diminishing Returns was in play here.
The Exogal Comet looks great and sounds even greater. Easy to set up and use, it has enough flexibility to serve as the front end of most systems, although the extremely low impedance of its analog input severely limits the analog sources it can handle. The idea of using a smartphone app as volume control is clever, and works very well. If headphone listening is a high priority, I’d look elsewhere; the Comet’s headphone amplifier is limited in power. As a DAC and front end for digital sources, the Comet is a spectacular success and, especially at its moderate price, I strongly recommend you audition it in your system. It represents Exogal’s very auspicious entry into the marketplace, and I look forward to hearing the company’s future products.