Abbingdon Music Research AMR DP-777 Digital Processor Tube DAC. "very best digital sound"

Beautiful black tube DAC by one of the best digital designers, AMR. Has all the inputs. Sounds great. The front is perfect and the top has little windows to vent the tubes and one section has some hazing.

Can be picked up at Chicago Axpona, if you call Midwest Audio.

Will be safely packed for shipping in the original shipping box with remote and manual. Paypal adds 3%. Checks welcome. Longtime trustworthy seller.
I am also an authorized dealer for Legacy Speakers, Auralic, Oracle, Resonessence Labs, Triangle Art, Coincident, and NAT Audio.

From Stereophile:

Computer audio is more than just a pleasant distraction. For the jaded reviewer, USB digital converters and the like are an escape from that humdrum, if only because they bring with them so many variables: myriad combinations of different platforms, storage devices, operating systems, device drivers, media players, codecs, word lengths, sampling rates, connection protocols, and more. Challenging though they may be, computer-audio products are a tonic for reviewers inclined toward apathy.

A new digital-to-analog converter from Abbingdon Music Research, the DP-777 ($4995), serves as a good example—doubly so, one might say. The DP-777 is literally two digital converters in one, incorporating separate processor chips to handle high-resolution files and "Red Book" CDs (and music files derived therefrom). The DP-777, being a clever thing, automatically chooses between the two, depending on the nature of the incoming datastream.

From there, more variables abound. The AMR converter offers the user choices of: five digital filters (two "Red Book," three hi-rez); six sampling rates; two jitter-reduction settings; word lengths up to 32 bits; and two modes of overall operation, to automate (or not) the preceding. There are five types of digital input jacks, two types of analog output jacks, and four levels of panel-light brightness. It also has analog inputs, to allow it to be used as a conventional preamplifier, and there is an optional volume control.

My wife and I have a standing joke: Whenever we find ourselves in a retail store with an overwhelming number of choices—10 varieties of Colgate toothpaste, six formulations of Advil, Gap jeans that hug the waist and thighs in a dozen different ways—we complain that life would have been easier in the old Soviet Union. We're kidding, of course.

Description
The AMR DP-777 is built into a generously sized aluminum chassis constructed from various extrusions, interior braces, and well-finished exterior panels. A digital display and five touch-sensitive control buttons take up the front panel—as one would expect, far more control options are available on the included remote handset—and the converter's top surface has two rows of Perspex windows that offer a glimpse of the various capacitors, oscillators, regulators, transformers, and tubes within.

Yes, tubes: Each channel of the DP-777 uses a Russian 6H1n-EV dual-triode as an output amplifier, one half configured for gain, the other half as a buffer stage. More significant, the DP-777 uses a Russian 6H11P dual-triode as an S/PDIF input amplifier on two of its digital inputs. As AMR sees it, S/PDIF is essentially an analog transmission protocol, traditional implementations of which use a positive-feedback mechanism that adds considerable distortion. Their tube-based signal amplifier, they say, which operates into a range of several hundred megahertz, is the best way to maintain the clean squarewave of the digital input.

This being 2012 and all, one might expect the buyer of an outboard D/A converter to have more interest in computer-audio sources than disc transports and the like; the engineering effort that AMR has brought to bear on the DP-777's USB input is thus unsurprising. And that effort has been directed by the notion that optimum playback quality is possible only when a recording's original sampling rate and word length have been carefully preserved and maintained. I can't help seeing a parallel between that point of view and the prevailing attitude among hardcore mono enthusiasts such as myself, who believe in matching stylus dimensions and playback EQ curves to different vinyl and shellac discs. Then again, given that AMR's chief designer is the well-known DIY guru and analog maven Thorsten Loesch, I believe I can be forgiven.

The heart of the DP-777 is its Gemini Digital Engine board, which is home to the twin processor chips mentioned earlier: a Wolfson 32-bit processor optimized for high-resolution files, and a Philips UDA1305 for more plebeian inputs. The proprietary AMR software that detects the incoming signal and selects the appropriate D/A processor resides in another chip on the same board (the one labeled V2.5, visible in the interior photo).

The DP-777 also has a Zero-Jitter Mode, which can be left on at all times or manually selected from the remote handset. AMR says that the Zero-Jitter Mode system determines the long-term average of the incoming signal clock, then uses a high-capacity memory module to dynamically match it to an accuracy of 0.001Hz. Separate from this, the AMR also boasts an asynchronous USB input, which keeps the converter from relying on the clock in the datastream supplied by the computer.

Construction and parts are all first rate. Tubes are surrounded by copper-foil shields, electrically grounded and physically damped with polymer rings. Transformers and even capacitors—the latter including some proprietary silver-mica film types—are custom-made for AMR. Layouts are clean and sensible, cooling is provided for, mass is sufficient to the task and not a gram more. Even the rubber feet, which make intentionally limited but stable contact with the surface below, are well thought out and, apparently, effective.

Installation and setup
The AMR DP-777 was no more difficult to install than any other USB DAC I've tried—by which token, one can also assume that it was easier to work with than even the least challenging wireless or Ethernet processor I've tried. On connecting the DP-777 to one of the USB ports on my Apple iMac (running OS X 10.6.7) and opening the System Preferences and Sound windows, I was presented with a device selection labeled "XMOS Processor"—not quite "AMR DP-777," but neither was it anything I'd seen on that list before. I clicked on it, and that did the trick. (I'm told that a dedicated device driver, which can be downloaded from the AMR website without charge, is required for use with Windows 7.)

Since its raison d'être is the ability to throughput virtually any music file at its native sampling rate, the DP-777's performance can only be gauged with a media player that itself adapts to such distinctions, preferably on the fly; thus iTunes would suit only the user who's willing to check each file ahead of time, exit iTunes altogether, manually change the file type in the Apple Audio MIDI Setup utility, then relaunch iTunes. And that is so not me. Luckily, I already own Decibel v.1.0.2, a program that plays any and every file size, natively and on the fly—and that's what I used, for the most part.

The folks at AMR were okay with that, but they recommended that I also download and try a media player called Audirvana. I've given it a whirl, and so far I'm impressed—but all of the listening impressions that follow are based on my experiences with Decibel. Given that the DP-777 itself presents so many user-selectable performance options, the addition of yet one more variable—one more unknown—was more than I could reasonably handle within the review period.

Using the DP-777's remote handset, I found it was easy to select from the various sampling rates, filters, and jitter-reduction settings on tap—or to simply trust the processor to make the best decisions for me. For the vast majority of my listening I chose the latter route, which required me to press just two buttons: Zero-Jitter Mode and AMR, the latter the DP-777's equivalent of autopilot. During use, the sampling rates, etc., of all music files (and S/PDIF sources, for that matter) were displayed on the DP-777's front panel, and all were reported accurately.

I experienced only one performance glitch during the review period: On a morning occasioned by an unusual amount of switching among different media players, the DP-777 apparently ceased to inform my computer of its presence. According to the computer's System Preferences window, it couldn't find the AMR at all. Rebooting had no effect; surprisingly enough, simply unplugging the USB cable to the AMR for a second and plugging it back in did the trick.

The DP-777 became slightly warm to the touch during normal use. Nevertheless, I kept to the manufacturer's recommendation and left the AMR powered up at all times.

Listening
Someone had put a few miles on my review sample before I received it, so I can't say how much running-in a brand-new DP-777 might require before sounding its best. I can say, however, that from Day One the AMR produced some of the least fatiguing, most involving, and altogether best-sounding digital playback I've had in my home. In much the same sense that EMT's extraordinary OFD 65 phono pickup made me wish I had twice as many 78rpm records in my collection, the AMR processor made me wish for double the number of music files on my hard drive.

The DP-777's characteristic sound was one of openness, a generous sense of scale, detail without artifice, and a barely perceptible but undeniably consistent timbral warmth. Regarding that last quality: From my listening notes, it appears that I originally reached for the word liquidity but crossed it out—probably because that descriptor is something I've come to associate with a plasticky lack of texture that I find more offensive and more tedious than almost any other shortcoming of digital sound. (That plasticky sound is something I also associate with the last very-large, very-high-tech, very-expensive digital processor of my experience.)

At times during the DP-777's stay in my home, its sound quality was nothing less than revelatory. While listening to a bog-standard CD copy of a much-loved bootleg, Procol Harum's Delicado (which found the band performing with the Los Angeles Symphony Orchestra on a good night in 1973), the clarity and the level of nuance and detail were beyond anything I'd experienced from the disc. A clarinet obbligato during the verses of "Fires Which Burnt Brightly"; the counterpoint supplied by the flutes in the final verse of "TV Caesar"; and guitarist Mick Grabham's glorious final note in the closing "Rule, Britannia" were all stunningly present. "My Little Shirtwaist Fire," from Rasputina's Thanks for the Ether (ripped from CD, Columbia CK 67504), didn't just sound more tactile: It was bigger and deeper, and the melody just plain moved, uncoiling like a spring from start to finish. And that's not to mention the texture and tone of the cellos, and the near-physicality of singer Melora Creager's exaggerated vibrato, all of which were stunning.

Orchestral music sounded especially grand through the AMR. Friedemann Layer and the Mannheim National Theaters Orchestra's live recording of Bruckner's Symphony 9 with a completion of the unfinished Finale (footnote ,1 ripped from CD, Deutschlandradio Kultur, no catalog number) was magnificent, with even more of the tension-and-release effect noted in the Rasputina track: The music moved forward humanly and, at times, unpredictably. The pleasantly brisk second theme of the first movement had far greater temporal energy through the AMR than through my reference converter, a Wavelength Proton USB DAC. Woodwinds and brass popped out of the thick orchestration in much the same manner I'm used to hearing live. String tone was luscious. And the intensity of the timpani was brilliant throughout. As my notes read: And this is digital?! Good grief!

Playback of high-resolution downloads was similarly impressive. Elton John's "First Episode at Hienton," from the HDtracks download of John's eponymous first US album, was smooth—but, again, not plasticky-smooth: There was still a good texture in the voice, strings, and Caleb Quaye's subtle, Leslie-amplified guitar, and the track maintained a human, organic feel overall. The sheer openness with which the AMR played the recent 96kHz version of George Harrison's All Things Must Pass was also impressive. Even "Run of the Mill"—the worst-sounding track on the album, for some strange reason—sounded less edgy, less congested, more open, and altogether more human through the AMR than through any other DAC at my disposal.

I did try the AMR's S/PDIF input, and was pleasantly surprised by the results. Driven from the transport of my Sony SCD-777, the DP-777 sounded distinctly warmer and more detailed than any of the Sony's filters, with greater musical nuance. The rich sound of Doc Watson's flat-picked guitar throughout the Nitty Gritty Dirt Band's Will the Circle Be Unbroken (CD, Capitol 5 35148 2) provided ample evidence of the latter, as did Dietrich Fischer-Dieskau's historic recording (with Gerald Moore) of Schubert's Die schöne Müllerin (CD, EMI 66959 2). With music of every sort, it seemed, the AMR provided more of a sense of touch, more momentum, more involvement than other converters.

What didn't it do? Although capable of sounding more substantive and forceful than through other digital sources of my experience, music through the AMR was still less so than most good vinyl (good defined as "played with an appropriately high-torque player and low-compliance pickup"), and wildly less so than shellac—although, in the latter case, I would blame the program and not the player. During the AMR's stay here, I was especially interested in hearing jazz from the late 1920s through the mid-'30s: mostly Louis Armstrong and Django Reinhardt. Digital transfers of recordings made during that time were all taken from 78rpm shellacs, of course, originals of which, in a very few instances, I'm fortunate to own. The admirably noiseless and durable CD transfers of those records are the most wretched, miserable failures imaginable when it comes to preserving and communicating the force, drama, substance, presence, and overall humanness of the originals—and the AMR could apparently do nothing to alleviate those shortcomings. (But, again, I wouldn't have expected it to: Too much of our industry's engineering community was long ago brainwashed by the small and smug notion that if something couldn't survive the trip through a Shure V-15 and a pair of Acoustic Research AR 3Axes, it wasn't worth hearing; consequently, all existing digital transfers of historic performances are scarcely worth having. Which is a damned shame.)

Conclusions
I could probably design my own loudspeaker if I had to, and I might even be able to sketch, on the cocktail napkin of your choice, a schematic for a simple tube amplifier capable of producing an audio-frequency signal (especially 60Hz). But I couldn't design a digital player or processor if my life depended on it—not even if you gave me a year to do it and a free trip to engineering school. That's just crazy.

But if I could do such a thing, all the while bearing in mind the enduring limitations of most digital recordings in circulation, it would sound like this one. For want of a better word, the Abbingdon Music Research DP-777 was friendly to literally all the digitally encoded music I played through it—friendly, but not blind to its endearing idiosyncrasies.

And while my budget doesn't allow for a $4995 digital source component, I think the AMR is reasonably priced, given both the (apparently unique) engineering on tap and what I heard.

For me, the AMR DP-777 was more than a pleasant distraction, more than just an escape from the humdrum; it provided some of the very best digital sound I've heard. Strongly recommended.

Description: Tubed digital-to-analog processor with volume control. Tube complement: two 6H1n-EV, one 6H11P. Sampling rates supported: 44.1, 48, 88.2, 96, 176.4, 192kHz. Maximum word length: 32 bits. Digital inputs: 2 S/PDIF (coaxial/TosLink optical), 2 S/PDIF (XLR/BNC), 1 USB. Analog inputs: 2 line level (RCA). Analog outputs: 1 RCA, 1 XLR (single-ended). Maximum output voltage: >2V. Signal/noise: >100dB, A-weighted (no reference level given). Channel separation: >90dB. Dynamic range: >90dB. Harmonic distortion: