Unison Research Sinfonia Integrated Amplifier
Thanks to Unison Research's extensive knowledge of output transformer production, the Sinfonia has been designed with a power stage that is made up of two KT88 valves per-channel in single-ended parallel ultra-linear configuration, in which the KT88 (beam power tetrodes) operate, with good approximation, like an ideal triode. This configuration provides very good results in terms of sound quality, however the natural drawbacks of valves (namely the non-uniform decline in performance over time due to drift) need to be addressed. So, after much testing, Unison Research developed an an original circuit design 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 quality even after many years, and also contributes to a slight reduction in the time it normally takes for the tubes to warm up after switching on and reach the optimal temperature.
The pre-amplification and the power stage drive are based on the double triodes ECC83 and ECC82. These valves guarantee excellent linearity and offer a nearly complete absence of odd-order harmonic distortion components. Both the stages are made up of triodes in parallel and are biased by automatic bias circuits. In this way the output impedance of the two circuits can be slightly reduced, which in turn improves the linearity of the stages. The signal-to-noise ratio and the total harmonic distortion improve significantly in this design as well. The direct current on the preamplifier valve filaments is supplied by an interesting circuit configuration: it works by directing the power stage valves cathode current through a parallel regulator which operates like a zener diode to the filament’s terminal.
The appearance of Sinfonia is both striking and functional. The control knobs are machined from solid, non-magnetic stainless steel and are weighted and balanced to provide a smooth, precise performance when used. The wooden parts, aside from their obvious visual beauty, effectively dampen out induced resonance in the metal chassis.The supplied infra-red remote handset allows for convenient control over input switching and the premium motorised volume pot from ALPS. The back panel is finished with six gold-plated speaker terminal connectors that allow the connection of 4Ω and 8Ω loudspeakers, alongside clearly marked gold-plated RCA inputs for multiple audio sources. In addition to the "Tape Out" connector is an additional low-impedance output terminal for connecting an active subwoofer; this terminal is linked to the pre-amplifier stage directly for reliable sub-performance. The source inputs have a buffer-stage to eliminate any negative effects connecting a subwoofer could have on the performance of the amplifier.
Key Features:
Dual mono Stereo Integrated Valve Amplifier
Single-ended Parallel Class A output stage KT88 valves used in sophisticated output stage design
Based on the superior Performance amplifier 27-30W output
Subwoofer output 4Ω and 8Ω loudspeaker terminals
Simply Phono power supply upgrade built-in
RC2 remote included
High-quality Cherry Wood finish*
Technical Data:
Type: Dual-Mono Stereo Integrated Valve Amplifier
Output Stage: Single-Ended Parallel Ultra-Linear Class A
Output Power: 25W
Inputs: 4 x Line 1 x Tape
Input Impedance: 47kΩ
Outputs: 1 x Tape 1 x Subwoofer Loudspeakers (bi-wiring)
Output Impedance: 4 - 8Ω
Feedback Factor: 14dB
Frequency Response: 20 - 30,000Hz
Valves: 4 x 6550 / KT88 2 x ECC82 2 x ECC83
Remote Control: IR control of inputs and volume
Power Consumption: 500W (max.)
Dimensions (W x D x H): 44 x 42 x 21cm
Net Weight: 55lbs.
*Sinfonia with Mahogany finish is available to Special Order.