Unison Research® is celebrating with a special edition of our most successful products: Simply Italy, Triode 25 and S6. The Black Edition boasts advanced technical and sonic performance, featuring a new cosmetic design with a piano black wood front panel, black gun metal finish, and updated lettering graphics.

General Overview

To improve the S6 we worked on its strengths and went even further to achieve higher sound quality.

The circuitry has been revised in the signal path and power management, again surpassing the milestones already achieved in the S6. Power output is now 40W, 15% more than the standard model. The polarisation of the power output valves has been completely revised to eliminate the capacitor and cathode resistor.

The input selection circuit has been implemented using the same technology designed for our most valuable equipment and extreme care has been taken in the design of the ground paths and channel separation. The valuable audio signal, where possible, travels protected in high-quality coaxial cables.

The S6 Black Edition amplifier is able to meet the needs of the most demanding users, featuring:

• Dual Mono amplification;
• Cathode Capacitor Less technology;
• unfiltered Sub output that maintains the sound timbre of the amplifier;
• input selection circuit implemented using micro relays and Return GND technology;
• in addition to the 4 analogue inputs, inside the amplifier there's the new DAC3, which adds 3 more digital inputs; USB (PCM up to 384kHz, DSD native up to 256x e DoP up to 128x), Tos-link e SPDIF up to 192kHz as standard.

Technical Insights

The original S6, introduced in 2001, featured auto-bias polarization. In 2011, the S6 New was introduced, featuring dual mono amplification and a mixed polarization, including auto-bias and negative grid, adjustable for each valve. In the latest Black Edition, the auto-bias system has been completely eliminated.

Exclusively employing Gold Lion valves, the amplifier comprises two double ECC83 triodes for the preamp section and six KT77 for power amplification. Carefully matched Gold Lion valves ensure superior technical and acoustic performance.

The first signal triode operates without feedback, polarized using the ionic polarization method refined by Unison Research® over decades. This polarization, coupled with the absence of feedback, results in improved micro-detail and a natural dynamic sound.

Power output valves are polarized using a dedicated negative grid voltage power supply, similar to the Simply 845. This polarization method allows for the elimination of electrolytic capacitors at the cathodes of the power valves, preventing capacitor phase shifting and coloration at low frequencies. Consequently, the frequency response extends to the lowest harmonics of the audio spectrum.

All power valves operate in Class A, in ultralinear configuration with a 20% tap. The output transformer, with 7 winding sections, is designed for maximum power transfer at an impedance of 6Ω, ensuring optimal compatibility with modern loudspeakers.

The power supply system has been significantly enhanced, decoupling the anodic voltage of each valve to ensure their independence. Additionally, strategically placed polypropylene capacitors have been added to the power supply, improving transient response and signal dynamics.

The input selection circuit has been meticulously designed to minimize noise and optimize channel separation. Micro relays with gold-plated silver contacts ensure stable contact over time and prevent crosstalk with other non-selected sources connected to the amplifier. Furthermore, the return grounds of the inputs have been implemented using Return GND technology, guaranteeing an individual path of reduced length for each input.