CD / SACD players and transports — Unison Research UNICO CD DUE

The UNICO CD DUE from Italian valve specialist Unison Research is a CD player with a valve output stage that also works as a stand-alone D/A converter for computers, streamers and phones. It plays audio CDs only and carries the UNICO name shared with the company's integrated amplifiers. The US list price is USD 5,499.

Key specs that matter

The digital section is built around an ESS Sabre ES9018K2M with its jitter eliminator, rated at 128 dB signal-to-noise (A-weighted, 0 dBFS, 1 kHz at 192 kHz) and 0.0003 percent THD+N from 20 Hz to 20 kHz. The USB 2.0 input, run by an XMOS interface, takes PCM from 44.1 to 384 kHz at 16 to 32 bits plus DSD128 and DSD256. Coaxial S/PDIF (0.5 Vpp, 75 ohm) and AES/EBU (2 Vpp, 110 ohm) accept up to 192 kHz and DSD64 over DoP, optical Toslink stops at 96 kHz, and Bluetooth 3.0 with aptX handles 44.1 and 48 kHz at 16 bits. Analogue signals leave through RCA and XLR sockets, and S/PDIF, AES/EBU and Toslink outputs pass the digital stream to other equipment. The chassis is 45 cm wide, 38 cm deep and 13 cm tall, weighs 10 kg and draws up to 100 W.

Engineering and use context

Discs load into a slim 8829CD-KHM drawer mechanism, enclosed and shielded by a thick metal cover. After the DAC chip, four 12AX7/ECC83 double triodes form a pure class A differential totem-pole stage, a topology that pairs triode gain with the drive capability of a cathode follower and supplies the balanced outputs directly. For listeners who want a solid-state path, an optional buffer built on AD8597 and AD8599 op-amps can be switched in from the remote, while relays keep it bypassed in normal use. Three digital filters are selectable by remote - fast roll-off with linear phase, fast roll-off with minimum phase and slow roll-off with linear phase. Status appears on a 128 x 64 white OLED graphic display that can be switched off entirely, and the infrared handset is made of wood and metal.

Pairing

Balanced XLR outputs make the DUE a direct match for amplifiers with XLR inputs, and the RCA pair covers everything else, including Unison Research's own UNICO integrated models. With a computer on USB and a phone over Bluetooth, the player can act as the digital hub of a compact system, while its digital outputs let an external converter be tried later without replacing the transport.

Alternatives

The Unison Research UNICO CD UNO is the simpler disc player of the range, using a single 12AU7/ECC82 double triode in class A followed by a discrete solid-state buffer.