S6

S6 is the latest project from the Unison Research® design team at A.R.I.A. Advanced Research In Audio Srl. It benefits from the vast experience gained over more than fifteen years in the design and manufacture of valve amplifiers within our company.
S6 is a single-ended integrated amplifier of high power and compact dimensions, capable of comfortably driving almost all loudspeakers including those of fairly low sensitivity.

Electronic Characteristics
The preamplifier stage consists of two directly coupled triode valves.
The output stage uses three EL 34-type valves for each channel, connected together in triple-parallel configuration and operating in single-ended Class-A ultralinear mode.
The output transformer - in the Unison Research® tradition - has been specially designed and handmade in our own workshops. It allows a very wide frequency response together with the highest possible sound quality.
Outputs are provided to cater for loudspeakers of both 4 and 8 Ohms.
The mains power supply transformer is of generous proportions and will provide all the energy that may be needed by the amplifier under all conditions of use.
During the development stage, great care was taken to design for the absolute minimum number of components in the audio signal path, and thereby allow a close approach to the theoretical ideal of unimpeded signal flow.
Last but not least, all connections to both inputs and outputs are gold plated, which will ensure excellent electrical contact over the lifetime of the product.

Appearance Characteristics
Traditionally at Unison Research®, the appearance design of our products is a matter of great importance and pride for us. By its own unique form and combination of chosen materials, each of our products is pleasing to the eye, and in its own way represents the skill, artistry and experience of our design team. S6 is a fine expression of the artistry for which Unison Research® is renowned throughout the world, and of which we are justly proud.
The appearance parts are handmade from finest quality solid hardwoods, and finished with natural organic lacquers.
The control knobs are stainless steel, precision made on numerically controlled machines for a high degree of accuracy and fine surface finish.
The design of all valve amplifiers needs to take account of the heat dissipation from the valves themselves, and in the case of S6 this has been turned into an attractive visual feature with the EL 34 output tubes arrayed in an arc, the stainless steel baseplate of which acts as a thermic reflector.
For the first time on a Unison Research © amplifier, a metallic protective grille is provided which allows the valves to be seen and enjoyed. At the same time the grille offers no resistance to the natural ventilation of the tubes.

Sonic Characteristics
Fine-tuning of the sound of the S6 was carried out during several months of careful listening tests, using a great variety of source components and loudspeakers. One of the most important results of this 'refining process' was the choice of how much negative feedback to employing the circuit design. The final figure chosen is a perfect compromise, giving precise detail and control but without losing any of that enchanting airiness, warmth and transparency for which well-designed single-ended amplifiers are renowned.