Setup
To isolate the amp from resonance nasties and rowdy FedEx trucks rumbling down my well-worn Greenwich Village block, I placed an Aptitlig bamboo cutting board underneath the S6 Black Edition. This, along with Norman Varney's EVPs (the best isolation pucks I've found for resonance control and noise reduction) placed under the Aptitlig, provided vibration isolation. To evaluate the S6 Black's internal DAC, I connected my Tascam CD 200iL CD player via a single Triode Wire Labs Spirit RCA cable running from the CD player's coax output to the S6's S/PDIF input. Biasing the KT77 tubes was quick and easy. Simply press the small metal button for the corresponding KT77, then use the opposing knob to adjust the needle within the bias window until it's as close to the center as possible. Throughout the review period, I periodically checked the bias, and it remained remarkably stable. Listening
Inspired by the YouTube channel Poetry on Plastic, I've recently been immersing myself in classical recordings on vinyl. A visit to VPI House in New Jersey, where Stereophile Managing Editor Mark Henninger and I interviewed VPI's Mat and Harry Weisfeld for the Stereophile Icons series, proved particularly fruitful. Harry shared a box of original Mercury Living Presence LPs, setting me on a path of sonic discovery and emotional overload.
The S6 Black Edition paired with the Volti Audio Lucera loudspeakers took to classical music as if to the manor born. True to its artistic heritage and legacy, the S6 served up a musical meal full of color, drama, and intensity.
The S6 Black presented Rimsky-Korsakov's Scheherazade, performed by the Minneapolis Symphony Orchestra under Antal Dorati (Mercury SR90195), with striking clarity. The performance showcased natural reed tone, rich violin and harp, and generally a captivating sense of immersion, this last quality a consistent hallmark of the S6. The music it made possessed a deep, dark-chocolatey richness while managing to avoid cloying sweetness or sentimentality. Its presentation was vibrant and full. The S6 expertly laid out the nuances of the Minneapolis Symphony with excellent layering and separation. During the opening, "The Sea and Sinbad's Ship," the S6 captured the music's surging intensity; the orchestra rose like a rogue wave, threatening total submersion in sound.
The S6 Black handled Respighi's The Birds, performed by the London Symphony Orchestra and also conducted by Dorati (Mercury SR90153), with similar aplomb. The Prelude is a brutal test of dynamics; the orchestra explodes from the first note. The S6 Black met this challenge, delivering a thrilling wall of sound without a hint of strain. The presentation was sweet and tuneful, rhythmically powerful, and dynamically graceful, swinging effortlessly yet compellingly from ppp to fff—power with finesse, rich texture, thrilling dynamics, all within a big soundstage with instrumental sections well delineated.
On Dorati's Conducts Wagner (Mercury SR90234), the swaying strings bristled with intensity and liveliness; they were never coarse. The S6 Black was a time machine and tone generator; the result was color, drama, and intense visceral impact.
Voxativ Ampeggio 2024
Navigating large floorstanding speakers in my cramped NYC apartment is a challenge, especially with records piled high in every corner. I replaced the Luceras with the Voxativ Ampeggio 2024 speakers, starting with the Ampeggios close to where the Luceras had been located; only minor adjustments were needed to get the sound I knew the Voxativs were capable of. The Voxativ Ampeggio 2024s are slightly less sensitive yet still very sensitive—a light load even for a low-power amplifier; the S6 Black's 40Wpc, specified into 6 ohms, should be ample.
Moving beyond classical but sticking to vinyl records, I played jazz from Count Basie, Anne Butterss, Steve Coleman, Dave Holland, and Bob Dorough. All shone through the S6 Black, leaving me wanting nothing except more of the same.
I mounted the Ortofon 2M LVB 50 moving magnet cartridge on my Korf TA-SF9R tonearm, which was attached to the armboard of my Thorens TD 124. The Ampeggio's laserlike focus created a different synergy than I'd heard with the Luceras. The upper treble lacked some of the ease I heard with the Voltis, but the music remained effortless and flowing, and the Ortofon/Unison Research/Voxativ pairing compensated with extra drive and emotive energy. The music was vibrant and intense, like a winter sunrise.
Another cartridge swap, Ortofon 2M LVB 50 to Kuzma CAR-30 MC. This change transformed the sound. Music became more sensuous, atmospheric, sweet. Listening to the Great Jazz Trio's Re-Visited (Eastworld EWJ-90005) or Kraftwerk's Tour de France (Kling Klang 50999 9 66109 16), the presentation became more glider-smooth, less bullet-train powerful, more silken. No matter what I paired it with, the S6 Black, with its signature golden hue and consistent well-sortedness, faithfully reproduced subtleties of the upstream and downstream components.
DeVore Fidelity Super Nine
With upstream components unchanged, I switched from the Voxativ Ampeggios to the DeVore Fidelity Super Nines, which, though still sensitive and an easy load, with a specified nominal impedance of 6 ohms, are less sensitive still than the Voxativs. The Super Nines interacted with my listening room and the S6 Black in entirely new ways, presenting a dramatically different sonic landscape than either the Voxativs or the Voltis. Sticking with Kraftwerk: Tour de France (side 1) is practically a travelogue in sonic form, and the S6–DeVore pairing gave it the full scenic treatment. The crystalline swooping hi-hats, four-to-the-floor bass-groove generator, and delicate synths melodies shimmered and shook, while the bass drum and sub-bass notes locked onto my room with the tenacity of a tapeworm. I'm pretty sure my neighbors thought I'd installed a car-sized subwoofer.
The Jazz Life (Candid 9019), from 1961, features a who's who of jazz legends: Mingus! Roach! Dolphy! It's the jazz equivalent of a royal family reunion with the royal family but with way better solos. Produced by another jazz legend, legendary jazz critic Nat Hentoff, this vinyl artifact isn't just musically impressive; it's also a gearhead's dream. The back cover lists the equipment used in the recording process: Neumann U 47 and RCA 44-BX mikes, a Neumann lathe with a Neumann ES 59 cutter for mono and a Neumann SX 45 cutter for stereo, an Ampex 300 recorder. You can smell the vacuum tubes.
The S6–DeVore pairing rendered The Jazz Life with captivating transparency and charm, and life-affirming flow. From the delicate nuances of Roy Eldridge's muted trumpet and the crisp articulation of Jo Jones's ride cymbal to the resonant depths of Charles Mingus's bass, every sonic texture was exposed with exacting clarity and a touch of romance. The soundstage was broad and deep, the listening immersive. Could I ask for anything more?
I dug out my Tascam CD-200 iL CD player to evaluate the S6's internal DAC. From vocalist Kristiana Roemer's House of Mirrors (Sunnyside SSC 1597) to keyboardist Martin Bejerano's #CubanAmerican (Figgland FR-003) to drummer Duduka Da Fonseca Trio's Rio Fantasia (Sunnyside SSC 1753), the sound was perfectly fine: quiet, even compelling, but nowhere near as engaging as my analog setup. If you choose to attribute this to my vinyl bias, fine.
To sum up the S6–DeVore combination: While perhaps less fresh-scrubbed than with the other combinations, the sound was more honeyed. Where the Voxativs put forward each musical piece with razor-sharp focus, the DeVores emphasized the big picture, the complete performance, the sum of the parts. With the DeVores, music felt less cerebral, gentler, more expressive. I'm tempted to write romantic. Atmospheric. Again, the S6 Black stepped out of the way, allowing the character of the other components to shine through. All three speakers I tried paired beautifully with the S6 Black Edition but with dramatically different results.
Conclusion
I don't wish to leave the impression that the Unison Research S6 Black Edition is totally self-effacing—that it totally vanishes into the music. It does have a sound of its own, classic tube sound: liquid, a touch warm, excellent tonal color. It's not old-fashioned or stodgy, but it's definitely not sterile. It does what none of the hybrids I've reviewed, for all their considerable virtues, can match: sound natural, relaxed, and effortless with both sweetness and exemplary resolution. At the same time, it starkly exposed the character of everything I connected to it. It's a special amp. Like the Mastersound 845 I reviewed in the May 2023 issue—also Italian—the S6 Black sounds balanced and plenty fast, with nothing off or unnatural. It drove all my (easy-to-drive) speakers easily. It looks great, and there's a small but significant bonus: The remote control works from any angle. From Italy to you, the S6 Black Edition comes highly recommended.
To isolate the amp from resonance nasties and rowdy FedEx trucks rumbling down my well-worn Greenwich Village block, I placed an Aptitlig bamboo cutting board underneath the S6 Black Edition. This, along with Norman Varney's EVPs (the best isolation pucks I've found for resonance control and noise reduction) placed under the Aptitlig, provided vibration isolation. To evaluate the S6 Black's internal DAC, I connected my Tascam CD 200iL CD player via a single Triode Wire Labs Spirit RCA cable running from the CD player's coax output to the S6's S/PDIF input. Biasing the KT77 tubes was quick and easy. Simply press the small metal button for the corresponding KT77, then use the opposing knob to adjust the needle within the bias window until it's as close to the center as possible. Throughout the review period, I periodically checked the bias, and it remained remarkably stable. Listening
Inspired by the YouTube channel Poetry on Plastic, I've recently been immersing myself in classical recordings on vinyl. A visit to VPI House in New Jersey, where Stereophile Managing Editor Mark Henninger and I interviewed VPI's Mat and Harry Weisfeld for the Stereophile Icons series, proved particularly fruitful. Harry shared a box of original Mercury Living Presence LPs, setting me on a path of sonic discovery and emotional overload.
The S6 Black presented Rimsky-Korsakov's Scheherazade, performed by the Minneapolis Symphony Orchestra under Antal Dorati (Mercury SR90195), with striking clarity. The performance showcased natural reed tone, rich violin and harp, and generally a captivating sense of immersion, this last quality a consistent hallmark of the S6. The music it made possessed a deep, dark-chocolatey richness while managing to avoid cloying sweetness or sentimentality. Its presentation was vibrant and full. The S6 expertly laid out the nuances of the Minneapolis Symphony with excellent layering and separation. During the opening, "The Sea and Sinbad's Ship," the S6 captured the music's surging intensity; the orchestra rose like a rogue wave, threatening total submersion in sound.
The S6 Black handled Respighi's The Birds, performed by the London Symphony Orchestra and also conducted by Dorati (Mercury SR90153), with similar aplomb. The Prelude is a brutal test of dynamics; the orchestra explodes from the first note. The S6 Black met this challenge, delivering a thrilling wall of sound without a hint of strain. The presentation was sweet and tuneful, rhythmically powerful, and dynamically graceful, swinging effortlessly yet compellingly from ppp to fff—power with finesse, rich texture, thrilling dynamics, all within a big soundstage with instrumental sections well delineated.
Advertisement
Voxativ Ampeggio 2024Navigating large floorstanding speakers in my cramped NYC apartment is a challenge, especially with records piled high in every corner. I replaced the Luceras with the Voxativ Ampeggio 2024 speakers, starting with the Ampeggios close to where the Luceras had been located; only minor adjustments were needed to get the sound I knew the Voxativs were capable of. The Voxativ Ampeggio 2024s are slightly less sensitive yet still very sensitive—a light load even for a low-power amplifier; the S6 Black's 40Wpc, specified into 6 ohms, should be ample.
Another cartridge swap, Ortofon 2M LVB 50 to Kuzma CAR-30 MC. This change transformed the sound. Music became more sensuous, atmospheric, sweet. Listening to the Great Jazz Trio's Re-Visited (Eastworld EWJ-90005) or Kraftwerk's Tour de France (Kling Klang 50999 9 66109 16), the presentation became more glider-smooth, less bullet-train powerful, more silken. No matter what I paired it with, the S6 Black, with its signature golden hue and consistent well-sortedness, faithfully reproduced subtleties of the upstream and downstream components.
Advertisement
With upstream components unchanged, I switched from the Voxativ Ampeggios to the DeVore Fidelity Super Nines, which, though still sensitive and an easy load, with a specified nominal impedance of 6 ohms, are less sensitive still than the Voxativs. The Super Nines interacted with my listening room and the S6 Black in entirely new ways, presenting a dramatically different sonic landscape than either the Voxativs or the Voltis. Sticking with Kraftwerk: Tour de France (side 1) is practically a travelogue in sonic form, and the S6–DeVore pairing gave it the full scenic treatment. The crystalline swooping hi-hats, four-to-the-floor bass-groove generator, and delicate synths melodies shimmered and shook, while the bass drum and sub-bass notes locked onto my room with the tenacity of a tapeworm. I'm pretty sure my neighbors thought I'd installed a car-sized subwoofer.
The Jazz Life (Candid 9019), from 1961, features a who's who of jazz legends: Mingus! Roach! Dolphy! It's the jazz equivalent of a royal family reunion with the royal family but with way better solos. Produced by another jazz legend, legendary jazz critic Nat Hentoff, this vinyl artifact isn't just musically impressive; it's also a gearhead's dream. The back cover lists the equipment used in the recording process: Neumann U 47 and RCA 44-BX mikes, a Neumann lathe with a Neumann ES 59 cutter for mono and a Neumann SX 45 cutter for stereo, an Ampex 300 recorder. You can smell the vacuum tubes.
Advertisement
ConclusionI don't wish to leave the impression that the Unison Research S6 Black Edition is totally self-effacing—that it totally vanishes into the music. It does have a sound of its own, classic tube sound: liquid, a touch warm, excellent tonal color. It's not old-fashioned or stodgy, but it's definitely not sterile. It does what none of the hybrids I've reviewed, for all their considerable virtues, can match: sound natural, relaxed, and effortless with both sweetness and exemplary resolution. At the same time, it starkly exposed the character of everything I connected to it. It's a special amp. Like the Mastersound 845 I reviewed in the May 2023 issue—also Italian—the S6 Black sounds balanced and plenty fast, with nothing off or unnatural. It drove all my (easy-to-drive) speakers easily. It looks great, and there's a small but significant bonus: The remote control works from any angle. From Italy to you, the S6 Black Edition comes highly recommended.
