Unison Research are expanding on their class-leading range of valve-based hi-fi electronics to produce their first ever dedicated headphone amplifier solution. The SH is a single-ended, two-stage full-valve headphone amplifier designed to accommodate traditional analogue and modern computer-based audio sources.
The SH began with the same basic remit as the coveted Simply Italy integrated amplifier; to produce a world-class sound from a specialised device using the best technology available. The result was a fairly simple, linear circuit that produces an output voltage which is more than capable of driving a wide range of headphones, while keeping distortion low throughout the frequency range. This allows the SH to deliver a consistent, coherent sound character when in use.
The input stage uses ECC83 valves, while the output stage uses one EL84 valve (both operating in triode mode). The benefits to using this specific combination of valves are in the reduced power requirements for how the valves are usually employed, resulting in extended life, and the EL84’s ability to drive an output transformer with optimal electrical and sound qualities.
The SH comes equipped with two headphone outputs, connected in parallel for easy switching between headphones, or to accommodate multiple listeners. There is also a “Sensitivity” switch, to ensure the widest possible range of headphones can be comfortably driven by this amplifier. When set to “High Sensitivity”, the output voltage from the amplifier is reduced, and at “Low Sensitivity” it is at its maximum. The added advantage of this switch is for maintaining optimal sound quality while listening to music at lower volumes.
In addition to a standard un-balanced RCA input for connecting any traditional analogue source, the SH is also equipped with a class-leading USB DAC. The asynchronous USB 2.0 technology is the same as found on the recent Triode 25 amplifier, and supports audio formats up to 384kHz PCM and DSD 128. The patented jitter-elimination circuit ensures a great sonic performance, assisted by the galvanic isolation employed between the power areas of the USB interface and the conversion IC. This additional input option brings SH up-to-date with the latest requirements of computer-based audiophiles.
With the use of an Apple lightning to USB connector (not included) you can plug your iPhone/iPod/iPad directly into the SH's DAC and play your hi-res music files straight from your device.
The reason for choosing a headphone-based product was so Unison Research could cater for the growing world of headphone audiophiles, offering them the best valve-based amplifier to enjoy. It’s very difficult for solid-state solutions to compete with the un-rivalled influence valves can have on audio performance, making the SH a must-audition for anyone who takes their sound seriously.