UNISON RESEARCH SH

Pre owned. In excellent condition. One minor sign of wear on the left side, as shown in the photos. Supplied without original packaging.

A headphone amplifier that combines the refinement of valve technology with modern digital capabilities, designed to deliver high-quality listening from both analogue sources and digital music files. Its two-stage, single-ended Class A architecture uses ECC83 valves in the input stage and EL84 valves in the output stage, both operating in triode mode, to produce a clear, natural and musical sound. The passive volume control preserves signal purity, while a sensitivity switch allows the amplifier's output to be adapted to headphones with different impedance ratings, maintaining high sound quality even at low listening levels.

The SH features two parallel-connected headphone outputs, making it easy to switch between listeners or share listening with another person without compromising sound quality. Connectivity includes an unbalanced RCA input for analogue sources and an asynchronous USB input compatible with USB 2.0 Audio Class. The USB interface supports PCM files up to 384 kHz and DSD up to 128x, with resolutions of up to 32-bit. The integrated DAC is based on the ESS Sabre ES9010K2M chip and incorporates jitter elimination circuitry, galvanic isolation between the USB interface and the conversion circuit, and a low-phase-noise clock powered by a dedicated clean-voltage supply section. These features help ensure precise, detailed playback with minimal interference.

The SH delivers a signal-to-noise ratio of 110 dB (at 1 kHz, A-weighted, 192 kHz) and total harmonic distortion plus noise (THD+N) of 0.008% (at 1 kHz, -3 dBFS), demonstrating its ability to reproduce music with transparency and dynamic range. By combining valve technology with a modern DAC, the Unison Research SH offers a versatile solution for high-quality headphone listening from both analogue and digital sources. It is handcrafted and designed for long-term use.

Technical specifications

• USB interface: Asynchronous USB 2.0 Audio Class compatible; supports PCM up to 384 kHz and DSD up to 128x; resolution up to 32-bit; ESS Sabre DAC with jitter elimination circuitry; galvanic isolation between the USB interface and conversion circuit; low-phase-noise clock powered by a clean-voltage supply section; SNR 110 dB (at 1 kHz, A-weighted, 192 kHz); THD+N 0.008% (at 1 kHz, -3 dBFS)
• Maximum output voltage: High sensitivity: 0.5 V at 150 ohms; 0.45 V at 33 ohms; 0.4 V at 10 ohms. Low sensitivity: 1.5 V at 150 ohms; 1.2 V at 33 ohms; 0.65 V at 10 ohms
• Frequency response: -0.1 dB at 10 Hz; -3 dB at 50 kHz (Low Sensitivity output, 33 ohms)
• Input impedance: 20 kΩ // 100 pF
• Sensitivity: 0.67 V input / 0.33 V output (High Sensitivity, 10 ohms); 0.67 V input / 1 V output (Low Sensitivity, 33 ohms)
• Input stage: Class A, ECC83/12AX7
• Output stage: Class A, 2 × EL84 connected in triode mode
• Inputs: 1 RCA line input; 1 USB input
• Outputs: 2 parallel-connected headphone outputs
• Feedback factor: 16 dB
• THD: Less than 0.2% at 1 kHz, 0.5 V; less than 0.8% up to 1 V (Low Sensitivity output, 33 ohms)
• Power consumption: 45 W
• Dimensions (W × H × D): 22.5 × 12.6 × 32.2 cm
• Weight: 6 kg