Unison Research S6
Retail Price: 3.200€
System: Pure Class A Single-Ended Tube Stereo Intergrated Amplifier
Output Stage: Single Ended Parallel, Ultraliner, Class A
Power Output: 2x 30/35W
Vacuum Tubes: 2 x ECC82, 6 x EL34
Output Impedance: 4, 8 Ohm
Bandwidth: 20-50.000 Hz
Inputs: 4x Line, 1x Tape
Input Impedance: 47 kOhm / 50 pF
Outputs: Loudspeakers, 1x Tape Out
Feedback Factor: 14 dB
Remote Control: IR for Volume
Power Consumption: 265 watt
Weight: 25 kg
Description: The Unison Research S6 benefits from the vast experience we have gained over more than 25 years in the design and manufacture of valve amplifiers. 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.
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 has been designed and built in the Unison Research tradition—which means each one is handmade in our own workshops. It provides both a very wide frequency response and the highest possible sound quality. Outputs are provided to match loudspeakers of both 4 and 8 Ohms. The mains power supply transformer is designed with generous proportions and will provide all the energy that may be needed by the amplifier under all conditions of use. During the development stage of the S6, great care was taken to create a design that contained the absolute minimum number of components in the audio signal path, thereby coming close to the theoretical idea of an unimpeded signal flow. Last but not least, all connections to both inputs and output are gold-plated, which will ensure excellent electrical contact over the lifetime of the product.
Traditionally at Unison Research, the appearance of our products is a matter of great importance and pride. 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. The S6 takes this approach to the limits: the exterior surfaces are handmade from finest quality solid hardwoods and finished with natural organic lacquers. The control knobs are stainless steel, precision-made with numerically-controlled machines for a high degree of accuracy and an extremely fine surface finish.
The design of any valve amplifier needs to provide for heat dissipation from the valves themselves. In the case of the S6, this has been turned into an attractive visual feature with the EL-34 output tubes arrayed in an arc on a stainless steel baseplate that acts as a thermic reflector. For the first time on a Unison Research amplifier, a metallic protective grille is provided that allows the valves to be seen and enjoyed during listening. At the same time, the grille offers no resistance to the natural ventilation of the tubes.
Fine-tuning of the sound of the S6 was carried out during several months of careful listening tests, using a large 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 employ in the circuit design. The final amount chosen is a perfect compromise, giving precise detail and control without losing any of the enchanting airiness, warmth and transparency for which well-designed single-ended amplifiers are known.