After many years of great success Unison Research have decided to propose a new updated and improved version of the S6.
In this new model, the configuration of the final stage was maintained with a Parallel Single Ended Ultra-Pure Class A. The polarization of individual tubes has been changed and transformed from fully automatic to mixed. About 2 / 3 Bias is obtained with a cathode- type auto polarization and a third from the fixed polarization.
The fixed polarization of each valve is adjustable through a potentiometer and an illuminated analog instrument (for each channel). The choice of the mixed polarization increases the efficiency of the final stage and reduces the factor of local feedback with an appreciable improvement in sound. The output transformer is a new design and has a fixed output impedance of 6 ohms.
As is known the nominal impedance declared for an acoustic diffuser is not very significant: the real impedance undergoes significant changes with frequency, and its value may even drop below the nominal value stated. In this regard it should be noted that all the speakers produced by Unison an Opera are in accordance with DIN specifications and never drops below the minimum values indicated by that rules (20% of the nominal value). The decision to standardize the output impedance to 6 ohms is aimed at optimally interface all speaker with nominal impedance of 4 or 8 ohms.
Particular attention was paid to the power stage: each preamp stage is decoupled and filtered separately.
The new S6 has also been redesigned from the mechanical point of view: the two channels of the amplifier no longer share a single printed circuit but are now separated in two circuits located on the right and left of the chassis. This solution has greatly improved both the crosstalk and the heat dissipation. In this way the temperature in the various circuits is more controlled in the interest of sound quality, stability, reliability and the very life of electronic components.
The S6 aesthetic has been totally renovated giving to the amplifier greater personality and refinement. In particular, the new front panel, with inlaid wood in contrast, shows the amplifier technology and highlights the unique “Made In Italy” taste.