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Unison Research S6 Black Edition integrated amplifier

Celebrated for its contributions to cuisine, music, and art, Italy boasts a rich cultural heritage and a history of profound significance to the world.

From the 1088 establishment of the University of Bologna, the oldest university in the Western world, to the invention of the radio by Guglielmo Marconi in the mid-1890s, Italy has been at the forefront of innovation and artistic pursuit. Modern Italy stands as a testament to its vibrant past.

"The Italian Renaissance, which began in Florence in the 1380s, marks the first moment when Europeans stepped away from the traditional and…

Unison Research S6 Black Edition integrated amplifier Page 2

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…

Unison Research S6 Black Edition integrated amplifier Specifications

Sidebar 1: Specifications

Description: Two-channel, tubed class-A, Ultralinear integrated amplifier. Tube complement: six KT77 Gold Lion; two 12AX7/ECC83 Gold Lion. Inputs: four single-ended (RCA), USB, S/PDIF, TosLink. Outputs: Two pairs loudspeaker output terminals, subwoofer (RCA). Power output: 40Wpc into 6 ohms (14.75dBW) specified at 5% THD. Frequency range: 15Hz–30kHz. THD+N: 0.5% at 1W. Total gain (from line inputs): 35dB. Input impedance: 50k ohms. Max. power consumption: 265VA.
Dimensions: 13.75" (349mm) wide × 17" (4312mm) deep × 8" (203mm) high. Weight: 55lb (25kg).
…

Unison Research S6 Black Edition integrated amplifier Associated Equipment

Sidebar 2: Associated Equipment

Analog sources: Thorens TD 124 with Korf TA-SF9R tonearm/HS-A02 Ceramic Headshell. Ortofon 2M LVB 50, Kuzma CAR-30 phono cartridges.
Digital source: Tascam CD-200 iL CD player.
Preamplifiers: Tavish Audio Design Adagio (phono).
Loudspeakers: DeVore Fidelity Super Nine, Volti Audio Lucera, Voxativ Ampeggio 2024.
Cables: Interconnects: AudioQuest Pegasus and Firebird, Triode Wire Labs Spirit II (RCA). Speaker: AudioQuest William Tell Zero (10'). AC: AudioQuest NRG Z.
Accessories: Pro-Ject VC-S2 ALU, HumminGuru record cleaning machines;…

Unison Research S6 Black Edition integrated amplifier Measurements

Sidebar 3: Measurements

I performed a full set of measurements on the Unison Research S6 Black Edition using my Audio Precision SYS2722 system. I carefully installed the tubes and after leaving the amplifier powered up for 30 minutes, checked that the bias for each of the six KT77 output tubes was correctly set. I rechecked the bias every 30 minutes during the testing.

Looking first at the S6 Black Edition's unbalanced line inputs, the input impedance measured 39k ohms at 20Hz and 1kHz and 36k ohms at 20kHz. The amplifier inverted absolute polarity at both the loudspeaker and…

Unison Research S6 Black Edition integrated amplifier More Measurements

To examine the performance of the S6 Black Edition's digital inputs, I used the coaxial and optical S/PDIF inputs—the optical input only accepted data sampled at rates up to 96kHz—and USB data sourced from my MacBook Pro. The USB Prober utility identified the S6 Black Edition as "UNISON USB DAC 2" from "UNISON RESEARCH," with the serial number string "0 (none)," and indicated that the USB port operated in the optimal isochronous asynchronous mode. Apple's AudioMIDI utility showed that the Unison Research accepted 16-bit and 32-bit integer data via USB sampled at all rates from 44.1kHz to…

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