Jason Victor Serinus returned to the Accuphase DG-68 in December 2021 (Vol.44 No.12):
There was nothing equivocal in my August 2021 review of the Accuphase DG-68 Digital Voicing Equalizer ($24,000). Calling it "among the most enlightening and consequential" audio products I've spent time with, I affirmed that it "enriched my experience of reproduced music far more than I could have imagined." I found it a transformational product that performed "flawlessly, to oft-astounding effect."
For better or worse, forces cosmic and otherwise left insufficient time to explore all the DG-68's many functions. When I evaluated the DG-68's "Auto Voicing" function, for example, I chose the connection path that the company seemed to favor: analog all the way. The only modification I made to my customary setup—Roon Nucleus+ music server via Ethernet–>Rossini DAC/Rossini Clock combo, XLR analog out–>D'Agostino Momentum HD preamp, XLR analog out–>D'Agostino Progression monoblocks (footnote 1)—was the insertion of the DG-68 in the analog signal path between preamp and amps. In doing so, I followed Accuphase's recommendation, on page 52 of their extensive, well-illustrated manual: "In general, we recommend configurations that place the DG-68 between your preamp and power amp."
When I subsequently questioned the company about this recommendation, Accuphase's Kohei Nishigawa replied by email, "The connection between preamp and power amp is the most traditional configuration. It has the most major effect. [Because] all signals from the preamp can go through the DG-68 processing circuit, the whole system will benefit from the DG-68. On the other hand, placing it between the DAC and preamp also has the advantage that, if the customer is really focusing on CD playback, this configuration brings out the best of the DG-68's ADC performance as the CD player's signal output level is quite stable." Since, in my system, the dCS Rossini Transport and DAC/Clock together amount to a three-piece "CD player" with SACD capability, this seemed an acceptable alternative placement strategy.
Nonetheless, Technical Editor John Atkinson pointed out that sending signal into and out of the DG-68 via analog requires two extra, unnecessary conversions inside the DG-68: from analog to digital before the DG-68's processing and from digital to analog after. Since I was working from digital sources, why not do the DG-68's DSP magic while the signal was still digital? Clearly the DG-68 was made to work that way; it has digital inputs and outputs. So wouldn't skipping those extra A/D and D/A conversions make the music sound better?
When I wrote Nishigawa-san about this, his reply was noncommittal. "We have tuned the sound better when the customer connects the DG-68 with analog in and out, than the analog connection without the DG-68, direct cable connection," he wrote. There was only one way to find out: Using the same music, compare the sound with analog in and out—the maximum number of conversions—vs the sound with digital in and out, which requires the minimum number of conversions. Logic and conventional wisdom suggested that the latter would sound best. But since when do logic and convention always rule in the audiophile kingdom?
After this comparison was complete, I intended to explore as many of the other DG-68 functions as my tight deadline allowed.
In all my tests, I matched levels using the technique long advocated by former editor (and current technical editor) John Atkinson and seconded by current editor Jim Austin (footnote 2). Each time I evaluated a different connection scheme, I set the Rossini's maximum output to 2V, set its volume to 0dB to eliminate any effect of the volume control on the sound, and relied entirely on the preamp to control the volume. Then I played the 1kHz @ –20dB test tone track from a WAV rip of the Stereophile Editor's Choice CD and adjusted the preamp's output level until voltage measured as close as possible to 2V AC at one of my Wilson Alexia 2's speaker terminals. Doing this eliminated any chance that different output levels caused by changes in connections and equipment order might fool me into favoring the sound of one connection scheme over the other simply because it was louder.
I used the same three tracks throughout most of the review: Eriks Eenvalds's "O salutaris hostia" from the Portland State Chamber Choir's superbly recorded Translations (24/96 WAV); the first two songs of Robert Schumann's Liederkreis, Op.24, handsomely performed by the resonant Icelandic bass-baritone Andri Björn Róbertsson with pianist Ástrídur Alda Sigurdardóttir on a new Fuga Libera recording, Thorsteinson & Schumann (24/96 WAV, FUG787); and Mozart's Overture from Le Nozze di Figaro, excitingly performed by Julien Chauvin and period instrument orchestra Le Concert de la Loge on the new Alpha recording, Mozart: Violin Concerto No.3; Symphony 'Jupiter'; Le Nozze di Figaro Overture (24/96 WAV, Alpha776).
That 2V output setting was a reference level not a listening level: It was too loud for that. But, with all three of these tracks, I could use the remote to lower the volume 14 steps on the preamp to achieve an appropriate listening level.
Reality checks
Reality Check #1: The DG-68 offers only three choices for digital in and out: coaxial (S/PDIF), TosLink, and the proprietary Accuphase HS-Link, which can only connect to other Accuphase products. Only the coax S/PDIF option was compatible with the Rossini's digital inputs and the cabling I had on hand. This left me with but one digital connection scheme. To go S/PDIF into the DG-68, I fed USB from the Nucleus+ into a never-released Wavelength USB-to-S/PDIF converter that Gordon Rankin gave me many moons ago. From the Wavelength converter, signal went S/PDIF (digital) out–>DG-68, S/PDIF (digital) out–>Rossini DAC/Clock, XLR (analog) out–>preamp, and XLR (analog out)–>monoblocks. Reality Check #2: Accurately comparing the DG-68's sound in analog in/ out to digital in/out required that I use the exact same components as well as matched volume levels. Hence, I always placed the Wavelength USB-to-S/PDIF converter between the Nucleus+ and whatever component followed, even when it wasn't necessary.
Reality Check #3: While the DG-68 offers both XLR (balanced) and RCA (single-ended) analog inputs and outputs, I stuck with XLR all the way in the initial review because the fully balanced D'Agostino preamp and monoblocks only allow XLR connections.
The analog signal path through the DG-68 to my monoblocks called for three pairs of Nordost Odin 2 XLR interconnects. My cable stash consisted of two pairs of XLRs plus two pairs of AES3 cables (footnote 3); I used one of the AES3 pairs in the original review. There's no technical reason why an AES3 cable can't be used for a balanced analog connection, but some companies' AES3 cables, including Nordost's, have a very different geometry than their XLRs. Upon further reflection, I wondered if this different geometry might have altered the sound.
To find out, I replaced the AES3 pair with RCAs in the only place where it was possible, between the Rossini and DG-68. This required a different equipment order than in my initial review, namely Nucleus+–>Wavelength converter–>Rossini DAC–>DG-68–>Momentum HD preamp–>M550 monoblocks.
In not so short order, it became clear that the AES3 pair was the weak link in my previous all-analog connection scheme. When I switched from AES3 to RCA, the sound was fuller, more detailed and colorful, and a bit more transparent. So, comparing best-case analog in/out to digital in/out required a change of cabling, a different component order, carefully matched volume levels, and the constant use of a Wavelength USB–>S/PDIF converter box.
If trying to visualize all this is giving you a headache, just imagine what it was like to ensure that, every time I made a switch, everything was connected optimally.
Reality Check #4: As explained in my initial review, I preferred the sound of the DG-68's "Flat" Auto-Voicing option to "Smooth," which boosts some frequencies for extra warmth. This preference continued when I switched to my new reference monoblocks, the Progression M550s, whose sound is warmer and smoother than the original Progressions. Hence, I did all my listening for this Follow-Up review in "Flat" Voicing mode.
As a first step, I created six new "Flat" Auto-Voicing compensation curves in the DG-68, one for each switch of component order and/or cabling. Only once did I forget to unmute the preamp, and only once did I risk my speakers when I forgot to turn off my monoblocks while moving cables around.
Are you surprised?
John Atkinson certainly isn't, and neither is Jim Austin. Digital in/out delivered the best sound through the DG-68. Even when I removed the Wavelength converter box, which was possible when listening in analog in/out mode, digital in/out with the requisite Wavelength converter box trumped analog in and out. On Eenvalds's "O salutaris hostia," digital in/out's transparency, range of colors, and depth won hands down. The clarity of voices, color contrasts between singers with different voice ranges, overall resonance of the soundstage, depth and sense of placement were top notch—the best I'd heard from my system. Although John Atkinson wasn't present when this track was recorded, he was responsible for the microphone placement and did a sensational job. He also used everything in his figurative toolkit to convey, in two-channel stereo, the emotional impact of antiphonal choirs placed throughout the recording venue. The DG-68's digital in/out connection not only delivered the all-important three-dimensionality that John strove for; it also compensated for my room's bass rolloff by bringing out all-important bass lines and fleshing out voices in ways not previously audible through my system. The sound was more substantial in the best ways possible without, to these ears, any loss in transparency, color, depth, and so on. The DG-68's digital in/out operation enhanced my listening experience in every imaginable way short of transporting me to the actual recording venue.
In case I don't have the opportunity to review bass-baritone Andri Björn Róbertsson's new recording in full, let me say how gratifying it was and is to hear the natural resonance of his beautiful voice fully fleshed out by the DG-68. With digital in/out, his voice sang out clearly over and in front of the piano, and the color contrasts between the two instruments were lip-smacking delicious.
Perhaps the biggest revelation was on the period instrument Mozart. Resolution was so acute that I could discern instrumental textures and distinguish individual instruments in the violin section as they played the same note in unison. I really could. While with analog in/out, lower lines lacked ultimate clarity, with digital in/out they sang clear and free.
Turning to a tried-and-true standby, the texture of the guitar that accompanies Rickie Lee Jones on her fabulous cover of the Stones' "Sympathy for the Devil" (Tidal, 16/44.1 FLAC), from her album The Devil You Know, and the resonance of the deep-voiced electronic instrument that appears in the intro were superb. I always thought my system could sound this good, but I never quite got there until I used the Accuphase DG-68 in digital in/out mode.
Roadblocks and revelations
Perhaps it's written somewhere in the Good Book that reviewing shall rarely go smoothly for an opera lover. But even I was unprepared for the denouement that played out just as the curtain was about to close on the last act of this follow-up review. Before I had time to grieve the death of a dear friend, a huge windstorm left the dogs barking arias on repeat as falling trees precipitated at least four power outages in our neighborhood. The outages took out the NAS that stored the hi-rez tracks I was using for this review and disrupted my internet connection for a miserable 36 hours, making file playback and streaming impossible. It was as if the gods were screaming "Vengeance is ours!" All that was missing was the arrival of a door-to-door audiophile evangelist holding up a copy of Michael Fremer's cartridge-setup DVD and urging me to repent my all-digital ways or risk being skewered by the spindle of a $400,000 turntable. Scrambling under deadline pressure, I grabbed umpteen cables, reconnected analog in/out on the DG-68, moved equipment around to free up another shelf on my rack, and installed the long-dormant Rossini SACD/CD transport so that I could play reference SACDs instead of files. It took overnight for previously coiled up cables to begin to settle in. It was not until a few hours before this follow-up was due that I was able to restore a wired streaming connection to the reference system (footnote 4). By then, there was no time left to return to digital in/out. In my original review, I explained that Accuphase makes a distinction between "voicing"—the term it uses to describe sound room correction—and "equalization," by which Accuphase means tailoring the sound to your particular (and sometimes changing) desires. In the initial review, I stuck with "Auto Voicing"; now I would try "Equalization" to further compensate for imperfections in the room response.
Roads less traveled
I also tried my hand at "Manual Voicing"—room correction but not automatic. The list of Accuphase's "Manual Voicing" possibilities rivals those on the family dinner menu of Chan's Casino, the Chinese restaurant my family frequented in Rockville Centre, New York, the town on Long Island's South Shore where I grew up many moons ago. I selected a preset curve in which the level drops off gradually starting at 2kHz, at a rate of 1dB per octave. I got as far as displaying the results in L+R channel, got confused, pressed the wrong button, and ended up with nothing. Fearing that if I dared extend the deadline even further, the opera I was in might morph into one in which I played John the Baptist and Jim Austin's Salome demanded my head on a silver platter, I opted to spare my life and move on.
Putting it all together
The more time I spent with the DG-68, the more I appreciated how much it can do, and how easy it is to play: to try things and listen and revise less than optimal choices or eliminate them entirely. With the caveat that, in my system, digital in/out clearly sounded better than analog in/out for transparency, clarity, depth, color saturation, detail retrieval, and more, I continue to recommend the DG-68 highly.—Jason Victor Serinus
Footnote 1: Those Progressions have since been replaced by Progression M550 monoblocks. Footnote 2: JA and I suggested using a suitable voltmeter to set levels at the speaker outputs. The specific implementation is all Jason.—Jim Austin Footnote 3: Pairs of AES3 digital cables? Yes, because dCS components use dual AES connections to transmit in higher resolution.
Footnote 4: I've had no time yet to deal with the NAS issue. The opera continues.
Reality Check #1: The DG-68 offers only three choices for digital in and out: coaxial (S/PDIF), TosLink, and the proprietary Accuphase HS-Link, which can only connect to other Accuphase products. Only the coax S/PDIF option was compatible with the Rossini's digital inputs and the cabling I had on hand. This left me with but one digital connection scheme. To go S/PDIF into the DG-68, I fed USB from the Nucleus+ into a never-released Wavelength USB-to-S/PDIF converter that Gordon Rankin gave me many moons ago. From the Wavelength converter, signal went S/PDIF (digital) out–>DG-68, S/PDIF (digital) out–>Rossini DAC/Clock, XLR (analog) out–>preamp, and XLR (analog out)–>monoblocks. Reality Check #2: Accurately comparing the DG-68's sound in analog in/ out to digital in/out required that I use the exact same components as well as matched volume levels. Hence, I always placed the Wavelength USB-to-S/PDIF converter between the Nucleus+ and whatever component followed, even when it wasn't necessary.
John Atkinson certainly isn't, and neither is Jim Austin. Digital in/out delivered the best sound through the DG-68. Even when I removed the Wavelength converter box, which was possible when listening in analog in/out mode, digital in/out with the requisite Wavelength converter box trumped analog in and out. On Eenvalds's "O salutaris hostia," digital in/out's transparency, range of colors, and depth won hands down. The clarity of voices, color contrasts between singers with different voice ranges, overall resonance of the soundstage, depth and sense of placement were top notch—the best I'd heard from my system. Although John Atkinson wasn't present when this track was recorded, he was responsible for the microphone placement and did a sensational job. He also used everything in his figurative toolkit to convey, in two-channel stereo, the emotional impact of antiphonal choirs placed throughout the recording venue. The DG-68's digital in/out connection not only delivered the all-important three-dimensionality that John strove for; it also compensated for my room's bass rolloff by bringing out all-important bass lines and fleshing out voices in ways not previously audible through my system. The sound was more substantial in the best ways possible without, to these ears, any loss in transparency, color, depth, and so on. The DG-68's digital in/out operation enhanced my listening experience in every imaginable way short of transporting me to the actual recording venue.
Perhaps it's written somewhere in the Good Book that reviewing shall rarely go smoothly for an opera lover. But even I was unprepared for the denouement that played out just as the curtain was about to close on the last act of this follow-up review. Before I had time to grieve the death of a dear friend, a huge windstorm left the dogs barking arias on repeat as falling trees precipitated at least four power outages in our neighborhood. The outages took out the NAS that stored the hi-rez tracks I was using for this review and disrupted my internet connection for a miserable 36 hours, making file playback and streaming impossible. It was as if the gods were screaming "Vengeance is ours!" All that was missing was the arrival of a door-to-door audiophile evangelist holding up a copy of Michael Fremer's cartridge-setup DVD and urging me to repent my all-digital ways or risk being skewered by the spindle of a $400,000 turntable. Scrambling under deadline pressure, I grabbed umpteen cables, reconnected analog in/out on the DG-68, moved equipment around to free up another shelf on my rack, and installed the long-dormant Rossini SACD/CD transport so that I could play reference SACDs instead of files. It took overnight for previously coiled up cables to begin to settle in. It was not until a few hours before this follow-up was due that I was able to restore a wired streaming connection to the reference system (footnote 4). By then, there was no time left to return to digital in/out. In my original review, I explained that Accuphase makes a distinction between "voicing"—the term it uses to describe sound room correction—and "equalization," by which Accuphase means tailoring the sound to your particular (and sometimes changing) desires. In the initial review, I stuck with "Auto Voicing"; now I would try "Equalization" to further compensate for imperfections in the room response.
Bass response in Jason's room without (top) and with (bottom) Accuphase DG-68 digital-domain "voicing."
After examining the "flat" before/after "Auto Voicing" compensation graphs I had created for the original review in analog in/out mode, I took note of the fact that there were two room nulls below 100Hz and another dip a little higher up in frequency; these are areas that "Auto Voicing" improved but didn't completely fix. Using the DG-68's supplied stylus, I lifted the output in these three narrow bands, drawing the corrections on the DG-68's large touch-activated display. It was as easy to do as drawing on an iPad with an Apple pencil. With file playback unavailable, I put on a Channel Classics SACD of Mahler Symphony No.3 in D minor (CCS SA 38817) performed by Iván Fischer and the Budapest Festival Orchestra and began to experiment with the DG-68's "Equalization" feature. Did these corrections help?
The results were, let us say, subtle. Did I hear any difference at all? I'm not sure.
Equalization, though, is flexible. You can try different things and see how they sound. If you like it, you can keep it, but if you don't, you can easily start over, or you can turn the feature off entirely. As I thought about it, I realized I could even attempt to raise bass so high that my system would begin to emulate the sound of the massive subwoofers in the trunks of the souped-up '93 Buicks and Pontiacs that shook our house years ago when we lived in East Oakland. But I decided not to make the attempt. I'd been rattled enough in the previous few days. Plus, I doubted I could ever get my system to sound that bad, no matter how sophisticated the tools.
I also tried my hand at "Manual Voicing"—room correction but not automatic. The list of Accuphase's "Manual Voicing" possibilities rivals those on the family dinner menu of Chan's Casino, the Chinese restaurant my family frequented in Rockville Centre, New York, the town on Long Island's South Shore where I grew up many moons ago. I selected a preset curve in which the level drops off gradually starting at 2kHz, at a rate of 1dB per octave. I got as far as displaying the results in L+R channel, got confused, pressed the wrong button, and ended up with nothing. Fearing that if I dared extend the deadline even further, the opera I was in might morph into one in which I played John the Baptist and Jim Austin's Salome demanded my head on a silver platter, I opted to spare my life and move on.
A moment from Mahler 3.
Finally, I opened the DG-68's "Analyzer" screen to display, in slowly changing spectrum, what the first movement of Mahler's Symphony No.3 looks like as it unfolds. This was one of the most fascinating exercises during my time with the DG-68. It didn't affect the sound, but it enriched my perception of it. Watching this was similar to what recording engineers see routinely. I'm not a recording engineer nor someone usually enamored of equipment with lots of flashing lights, but this was interesting.
The more time I spent with the DG-68, the more I appreciated how much it can do, and how easy it is to play: to try things and listen and revise less than optimal choices or eliminate them entirely. With the caveat that, in my system, digital in/out clearly sounded better than analog in/out for transparency, clarity, depth, color saturation, detail retrieval, and more, I continue to recommend the DG-68 highly.—Jason Victor Serinus
Footnote 1: Those Progressions have since been replaced by Progression M550 monoblocks. Footnote 2: JA and I suggested using a suitable voltmeter to set levels at the speaker outputs. The specific implementation is all Jason.—Jim Austin Footnote 3: Pairs of AES3 digital cables? Yes, because dCS components use dual AES connections to transmit in higher resolution.
