Like most modern amplifiers, the S6 keeps things simple. It offers five unbalanced line inputs, a set of tape outputs and a single set of loudspeaker outputs. There’s no built-in phone stage and no socket for headphones. The volume and input selector knobs have a nice solid feel and the amplifier comes with a handsome wood-clad remote control that looks like a late ‘80s mobile phone.
Six El 34 output tubes are used (three per channel) along with a pair of ECC 82s. Each output tube features user-adjustable bias and there’s a moving-coil meter to help the value to be set correctly.
The S6 produces a very rich smooth alluring sort of sound that is found immediately likeable. It delivers a big weighty sort of presentation that’s full-bodied and solid. There’s something ‘right’ about the combination of incisive clarity and rich pungent depth it offers.
At the same time, bass and treble extremes remain beautifully balanced and integrated, so that the higher frequencies never ‘lead’ the midrange and bass. The bottom end is clean and firm – maybe not quite as deep and powerful as certain direct-coupled transistors designs, but solid and weighty when it counts and free smearing and boominess.
Unison Research’s S6 sounds absolutely gorgeous, delivering that sweet glowing richness that tubes are famous for, without loss of bite or immediacy. Indeed, it’s the combination of silky smoothness and crisp immediacy that is so alluring.
S6 is one of those tube amps that’s very good at covering its tracks. It recreates the music with little sense of strain and sounds as though it has power to spare