This explains why the chance to review the latest DAC from Audio Research gave me mixed emotions. Sure, Audio Research has a legendary reputation, but the last time I had any of their gear in my system was back in the early '90s, during the beginning of their "Let's try this without tubes" era, which did not, in my opinion, yield the best results. All of Audio Research's DACs since the DAC3 in 1994 (with the exception of their latest Reference-series DAC) have been tube-free, and my bias was tough to shake.

But as soon as I saw that the new DAC9 came equipped with 6H30 vacuum tubes and could handle just about all of the latest high-resolution formats, I was intrigued. If any company could properly integrate vacuum tubes into a digital product, Audio Research could, given its reputation for innovation with this decidedly 20th-century technology.

The DAC9 is a fully balanced design and is part of Audio Research's new Foundation Series of entry-level components, but its specs are anything but basic. In the DAC9 architecture, which utilizes Burr-Brown TI PCM1792A DACs, native DSD files are converted to a true Direct Stream Digital signal at 2.824 or 5.6448MHz. DSD-to-PCM file conversion is unnecessary because the DAC9 uses two separate digital paths, one for PCM files and the other for serial DSD files at 1x to 2x DSD clock rates. Native DSD and DSD over PCM (DoP) are handled via USB, but only for Windows users at this time. Mac users will gain this functionality soon. More on that later.

Audio Research started using quad DACs several years ago with its DAC8, and the approach continues with the DAC9. Each channel utilizes dual stereo DACs running in mono, which the company says lowers the noise floor and increases dynamic range. A more common practice in the industry is to use one stereo or two mono DACs.

When it comes to time-domain challenges, the team at Audio Research chose to employ two distinct TCXO crystal master oscillators to handle different sample rates. The company explains that these oscillators enable the DAC to automatically select the proper clock, and they contend that this approach completely eliminates interpolation errors that normally degrade sonic purity.

What really caught my attention was the DAC9's zero-feedback, class-A analog section. It's here where the 6H30 vacuum tubes are directly coupled to the D/A converters. The Audio Research team is proud of the fact they've done this without coupling capacitors, an approach that would diminish low-frequency response. I've long suspected that a DAC's output stage is far more important than some audiophiles' almost single-minded obsession with ever-increasing file resolution would indicate.

Keith Carlson, the company's Director of Engineering, makes no bones about saying that the DAC9 is the most technologically advanced digital product Audio Research has ever created. In fact, Audio Research's Brand Manager, Dave Gordon, and Carlson believe that the DAC9's digital stage soundly outperforms those in the well-reviewed and considerably more expensive Reference DAC and Reference CD9. Carlson points to the placement of a 32-bit digital processor between the DAC's digital and analog output stages as one reason for what he believes is the DAC9's outstanding upsampling performance. On the other hand, he's quick to point out that the DAC9 still can't match the Reference products' superior analog stages, which are vacuum-tube regulated and come equipped with four tubes each. I guess that level of performance is what savings accounts are for.

While the DAC9 retains the classic industrial rack-mount design of all Audio Research equipment, its silver, anodized aluminum front (the unit also comes in black) has been freshened up a bit by Sonus faber's Livio Cucuzza, the designer who has led a number of cosmetic innovations at Audio Research's parent company, McIntosh Group. The neat row of round silver buttons underneath the display are reminiscent of the company's Reference line, and the easy-to-read display panel lends a subtle elegance to the unit. One thing that surprised me about the DAC9 was that, in spite of its substantial dimensions (19"W x 6 1/2"H x 13 3/4"D), it weighed a mere 14 pounds, easily the lightest high-end DAC I've ever encountered. Nonetheless, the fit and finish of the chassis and internal electronics have a solid appearance and feel that implies hand-built with meticulous attention to detail.

etting up the DAC9 for PCM playback was very straightforward. The first thing to do was take the aluminum top off the unit with the supplied screwdriver and install the hand-matched 6H30 tubes. Then you simply plug in your sources via USB, S/PDIF, AES/EBU, BNC or TosLink cables and turn the unit on. The display panel will flash the word Mute for 45 seconds until the circuits have reached optimal temperature, and then it's time to enter the names of your sources if you're that organized. I'm not, so I just fired up the rest of my system and hit Play. One particularly nice feature is an Hours button that, when pressed, displays how long the tubes have been in operational mode. Audio Research recommends that the 6H30s be replaced after 4000 hours in order to maintain the DAC9's peak performance.

The only issue I had during setup involved my Auralic Aries streamer. For reasons neither I nor the folks at Audio Research could figure out, the DAC9 could not recognize 192kHz files when sent from the Aries' RCA S/PDIF output, no matter what digital cable I used. So I simply selected the AES/EBU and USB outputs for listening to high-resolution PCM files. My PS Audio PerfectWave transport had no trouble sending 192kHz files to the DAC9's RCA input. Keith Carlson told me he plans on investigating the issue further as soon as he can get his hands on an Auralic Aries streamer. This is the not the first time I have encountered minor communication issues between two digital components made by different manufacturers.

I should also re-emphasize here that as of the time of this review, Audio Research was working on a way to enable Mac users like me who also own devices that use Linux (the Aries) the ability to enjoy the DAC9's DSD capabilities. Audio Research's Carlson said a fix would come either in the form of firmware or field-installable hardware sometime in 2017. In March of this year, the company announced that DAC8 owners can now have their units upgraded to handle Mac USB protocols. Because I don't have access to a Windows computer so that I could download Audio Research's DSD-capable Windows-based USB drivers, I was unable to assess the DAC9's DSD performance.

As with all Audio Research equipment produced during the past decade, the company recommends 600 hours of break-in for the DAC9. This is due, in large part, to the DAC9's proprietary capacitors, which I speculate may have some Teflon in them. While the DAC9's performance was nothing short of impressive during the first dozen hours of playback, there were some pretty dramatic shifts after that, which is right in line with what I've experienced with Teflon capacitors. Unless you like having your assumptions challenged every other day, I suggest waiting until at least 200 hours before launching any critical listening sessions. The balancing of frequencies and bloom around instruments continued to become more natural right through to the 600-hour threshold.

While the stock power cord that comes with the DAC9 is better than some, it should come as no surprise that shortly after the break-in period, I replaced it with a Shunyata Zi-Tron Sigma Digital, and the resulting improvement in dynamics and the lowered noise floor were immediately obvious. The people at Audio Research encourage the use of high-quality power products with its equipment, and they will get no argument from me.

f you want to have a little fun, visit an audio salon or show and ask other people there, "What're you looking for today?" I do this from time to time, and the results never fail to reveal a lot about our hobby. The standard response is usually something along the lines of, "I'm looking to upgrade my [insert equipment here] and get something that has better [insert favorite audio obsession]." While it's understandable, this answer reflects a point of view that cost me a lot of money over the years and gave me not much to show for it. Eventually, I was lucky enough to meet some wise, old veterans who taught me that music can be ruined by deconstructing its elements and focusing on one aspect or another. Chasing after thunderous bass or an enormous soundstage or fetishizing the latest file format will get you exactly that, but it won't necessarily bring you closer to a performance or, more importantly, to the essence of the music. The essence: that's a ridiculously, hopelessly subjective term, but it's the whole dang shooting match as far as I'm concerned. I want an emotional connection with the music I'm hearing. Once I have it, I tend to get off the equipment merry-go-round.

And that's pretty much where I was when the DAC9 arrived on my doorstep. My system was viscerally satisfying, and I was happy. But an afternoon with the DAC9 changed all of that. It stomped into my staid, comfortable audio/living room and started singing, shouting, dancing and turning over furniture. No more background music for you, it seemed to say. Whether it was Beyonce's bouncing rhythms or Jordi Saval's lilting strings, the DAC9 demanded my attention with detail and color I'd simply never experienced from any digital device I've had in my system. Furniture? Really? Well, the DAC9 might not have actually tipped anything over, but it certainly rattled a few picture frames with its textured, subterranean bass. The DAC9 is an intense party animal that also has the ability, when the lights are low, to calm down, clean up and turn into a refined host, as it serves up even the softest and subtlest details of a Debussy recital or the barely audible intake of breath between the phrases of a low-key Sinatra torch song. Simply put, the DAC9 is not an audio device you can ignore.

In order to explain how the DAC9 handled ordinary Red Book recordings, I'll start with Shawn Colvin's 1989 release Steady On [Columbia CK 45209], produced by studio wizard Jon Leventhal. The CD is one of the best Americana releases from that era, but it still suffers a tad from what I call '80s dryness. The DAC9 doesn't cover up this flaw, but it brings out so much of the air, ambience and separation that all of the recording's transgressions are quickly forgiven. On the title track, which I swear I've heard hundreds of times, I suddenly discerned individual male and female voices of a backing chorus that could be heard in the shadows, just a few feet from the spotlight of the lead vocal. After all of these years, how had I failed to notice that musically rewarding detail? On every single subsequent track, my already considerable respect for Colvin and Leventhal grew. The layers of instruments and subtle touches the duo packed into what must have been a moderately budgeted debut recording only became fully apparent to me after listening to it through the DAC9.

One of my favorite CDs of the early 2000s is Frou Frou's Details [MCA 586996]. This album launched the career of multi-instrumentalist and singer Imogen Heap, but her musical partner, Guy Sigsworth, never gets his due for the incredible production on this baroque pop masterpiece. If CDs wore out, I would've had to replace this disc years ago. I know the music on it so well that I can hum the next track before it begins. Nonetheless, the DAC9 produced a remaster free of charge. Sigsworth's synthesizer tweaks and Heap's angelic vocals swirled around me as though I were in the middle of my surround system. Just as I felt Sigworth's subterranean bass and drum tracks in my very bones, I was able to also perceive the subtlety of Heap's presence as she moved around the microphone throughout the complex mixes. All of this wasn't mere sonic gymnastics; it added to the music, making it more intelligible and whole -- just what a great audio component should do.

In the same vein, the DAC9 produced the kind of instrumental separation and impressively expansive soundstage that anyone who enjoys live music will find immediately addictive. If you're interested in every little bit of musical information zeros and ones can provide, the DAC9 will deliver the goods. On the track "Hear Me Out," I always knew that the duo had sampled, synthesized and looped one of Heap's vocal tracks to begin the song, but I was never able to hear that Heap is actually saying the words "I'm not over you" throughout the loop. One of the great strengths of the DAC9 is its ability to deliver incredible detail without ever committing the cardinal digital sin of overarticulating.

So, how does the DAC9 handle high-resolution recordings? It made me forget what sort of source I was listening to. Everything I've described so far about its character applies equally to high-resolution formats as well as lower-resolution streaming from services like Pandora and Spotify. It all sounds believable. Sure, the AES/EBU input might have had a slight edge over the S/PDIF in terms of delivering the very finest nuances, and both of those inputs were a bit more detailed and natural than the USB input (no surprise), but the fact that all of the inputs delivered organic, flesh-and-blood sound was impressive. The same can be said for high-res files versus good old Red Book material. My 96kHz HDTracks download of Beck's Morning Phase [Capitol Records] sounded even more dynamic and detailed than the CD [Capitol B00198302] when played through the DAC9. But this was the kicker: I would rather have listened to the Red Book version of this release through the DAC9 than the high-resolution download through any other DAC I've had in my system. Regardless of format, the DAC9 delivered the lowest lows, the clearest highs and all the important micro details necessary for a recording to be musically and emotionally engaging.

Whether I was playing the incredible 192kHz HDtracks download of Mel Tormé Swings Shubert Alley [Verve/PolyGram] or my highly curated Xx station on Pandora, everyone who heard the DAC9 and was familiar with my PS Audio DirectStream DAC remarked that the music was more captivating than before. My wife, who's a music lover but works as a financial analyst, called the sound "more impactful." (That's how analysts talk.) My friend Steve the Architect, a Magnepan fanatic, commented that "This DAC just gets out of the way. You forget about the gear and concentrate on the music." Fellow TAB writer Mark Blackmore said, "This DAC brings my attention to recording decisions I've never thought about before." My wife and I had a string of non-audiophile guests who stayed with us during my time with the DAC9, and in every single case their visits turned into listening parties that lasted late into the night and early morning. It has been my experience that people love to make requests when they're moved by the music.

Like many modern converters, the DAC9 is capable of native sample-rate upsampling of PCM files, but Audio Research engineers decided to make it a one-button choice: when upsampling is selected, all files are elevated to either 354.8 or 384kHz. In keeping with this simple-is-better approach, users are also given the option to employ just two roll-off filters: Fast (a brick-wall filter at the highest frequency) and Slow (a filter with a more gradual roll-off). I've never been a button fiddler, so this straightforward approach was refreshing. Differentiating between A and B is much easier than muddling through A,B,C, D and sometimes E. In the end, my clear preference was for the Slow filter because it sounded more organic and natural to my ears.

As far as upsampling was concerned, I preferred the native mode for most of my reference recordings because I generally like my best bourbon served neat. However, when releases were less than top-shelf, the upsampling option was very useful. For example, on "The Mooche" from Louis Armstrong and Duke Ellington's The Great Summit: The Master Takes CD [Roulette Records/Blue Note 5245472], the DAC9's upsampling option put me back a few rows from the stage. This was a good choice to have, given how much Armstrong was pushing the boundaries of his microphone during that particular number. To my ears, the upsampling option seemed to smooth things out a bit, making everything sound a bit more laid-back in presentation, something that benefited a number of harsh-sounding recordings that would normally have me reaching for the volume control.

t's reasonable to wonder whether the DAC9 would exhibit all of the characteristics I've described above in other systems. While I was unable to bring my unit to any of my friends' systems, I did make a major system change during the review process when I replaced my Thiel CS3.7 speakers with a pair of Wilson Audio Sasha W/P Series 2s. Even though both of these speakers are expertly engineered and highly refined transducers, the Sasha 2s are considerably more revealing and extended in all frequency directions than the Thiels. Consequently, the Sashas served to further underscore the considerable performance differences between the DAC9 and my PS Audio DirectStream DAC ($5999).

While I was enthralled by the DAC9's energetic character, I could imagine that its sizzle and utter transparency could come across as too much of a good thing in some systems or to some listeners. The DAC9's mission seems to be about delivering the unvarnished truth of a recording and bringing listeners closer to the performance. While I loved the detail, I'll confess that sometimes my Thiels occasionally objected to the very defined leading edge of transients the DAC9 served up.

While the DirectStream DAC's relaxed presentation was welcome when listening to harsher or edgier recordings, the price for that different approach was a reduced sense of realism across the board when compared to the DAC9. Some listeners with forward-sounding systems might prefer the DirectStream's more sedate approach, but to my ears the DAC9 was more transparent and honest to source, and thus more compelling, because of its better retrieval of detail, clearer three-dimensional presentation of voices and instruments, and firmer, more deeply textured bass.

I was a bit disappointed that the DAC9 doesn't offer a variable output. Such a feature would be useful to me because my Convergent Audio Technology preamplifier's manual volume control only allows adjustments in 3dB increments. On some recordings, the sweet spot lies somewhere between steps, and my DirectStream's variable output allows for a more finely tuned setting. For those seeking a volume control knob and even more tube magic, you'll have to step up to Audio Research's twice-as-expensive Reference Series DAC.

The DAC9's current inability to deliver DSD through a Mac's USB output was unfortunate, but this is a problem the company promises will be fixed before the end of the year, and the company's well-known service track record is an indication that this will happen.

With regard to Master Quality Authenticated, or MQA, the hottest topic among format chasers right now, Audio Research officials would only say that the company is "open" to the new technology. That seems fair, given how much the "Yes, you can; no, you can't" part of the MQA compatibility process has shifted during the past six months. For example, as I write this review a number of streamer manufacturers have announced that they are working on software that will enable their devices to perform the first two stages of unfolding MQA files in much the same way that the current Tidal desktop app can perform that function. Consequently, a considerable number of DAC manufacturers have chosen to wait for the proverbial dust to settle.

started the process for this review last year a very satisfied audiophile. But this DAC gave me a jolt of something I'd been missing. Several months of daily listening as well as a dramatic change in speakers did nothing to change my belief that the DAC9 is something special. Because of the immense amount of musical information it extracts from all source material, it comes closer to delivering the kind of realistic timbre, dynamics and three-dimensionality I've come to expect from great analog gear than any other digital source I've heard in my system.

Science fiction author Arthur C. Clarke once wrote, "Any sufficiently advanced technology is indistinguishable from magic." The Audio Research DAC9 performs a particular kind of magic I simply can't get enough of; it fools me into thinking that my living room is full of musicians and singers from around the world and keeps me listening until I lose all track of time.

The highest recommendation I can give a product is to buy it, and that's exactly what I've done here. For anyone else considering an audition, let that be a word of caution. The DAC9 is a stunning piece of musical equipment that you just might not be able to resist. I couldn't -- it's my new reference.