Unison Research Sinfonia Pure Class-A Integrated Valve Amplifier

Unison Research Sinfonia is a Dual Mono/Stereo pure Class–A integrated valve amplifier sharing design philosophy and winning look with the world-renowned Performance model. Pre-amplification and power stage drive are based on double triodes ECC83 and ECC82. This valves guarantee excellent linearity and nearly complete absence of odd order harmonic distortion components.

The power stage features a pair of KT88 per channel connected in parallel and working, thanks to the particular elaboration of the output transformers, in single-ended ultra linear configuration.

All the valves are rigorously selected and matched. Moreover, our long observation and in depth understanding of  valves behavior has lead to the design of an original circuit which, through the control of the KT88 bias, ensures a real time compensation of the parameters affected by drift. This solution guarantees the best sound performances even after years.

Inside the Sinfonia

As usual for high quality integrated amplifiers, the new model is laid out in dual-mono configuration: within a single chassis there are two identical and fully independent amplifiers so to avoid any possible electrical or electronic interference between the two channels.

Each amplification stage is entrusted exclusively to valves, and all operate in pure class-A.

The power supply is constituted by two toroidal transformers, one per channel, especially designed to minimize the magnetic flux dispersion.

The Sinfonia has a microprocessor-based circuit that controls the switching of the input selection relay and the volume level adjustment through the remote IR handset. The analog volume regulation is operated by a high quality ALPS RK27 stereo motorized potentiometer. 

External parts

In the Sinfonia nothing has been left to chance: from the choice of components, the control knobs and the wood parts, to the design of the chassis and the circuits boards.

Control knobs are machined from solid amagnetic stainless steel. Thanks to their weight, mass and balance, they provide smooth and precise control when operated manually.

The wood parts, besides the visual appearance function, also play another critical role: they contribute to damp out induced resonance in the metal chassis. Thanks to this structural damping the valves themselves, which like all vacuum tube devices are susceptible to microphony, are much less liable to generate unwanted resonance-related effects.

For the best reliability and long term musical quality, all the components used in the SINFONIA have been chosen with care: from the non inductive resistors and the filter capacitors, to the pure ceramic valve bases and the vetronite printed boards.

The dimension, the distribution and the lay out of the PCBs have been accurately studied and optimized to limit electrical disturbances and prevent components overheating.

Specifications

• Type: Dual Mono/Stereo Integrated Valve Amplifier
• Output Stage: single ended parallel ultralinear class-A
• Output Power: 25W
• Inputs: 4 line, 1 tape
• Input Impedance: 47 kOhm
• Outputs: 1 tape, 1 subwoofer, loudspeakers bi-wiring
• Output Impedance: 4 – 8 ohm
• Feedback factor: 14dB
• Frequency Response: 20 – 30000 Hz
• Valves: 4 x 6550/KT88, 2 x ECC82, 2 x ECC83
• Remote Control: IR inputs and volume
• Power Consumption: 500W max
• Dimension: 44 x 42 x 21 cm.
• Net Weight: 55 Ibs