UNISON RESEARCH REFERENCE MONOBLOCKS

Second-hand, in good condition, the power amps have some scratches (see pictures). Without their original packages.

good on consignment

Born from an ambitious design vision, this amplifier represents the pinnacle of decades of expertise in valve system engineering, concentrated in a pair of monoblocks that embody the full technical and sonic mastery of Unison Research. Every detail—from the selection of tubes to the transformer design—reflects the brand’s pursuit of excellence, delivering unmatched sound quality even at high power levels.

At the heart of the Reference is a pure Class A single-ended output stage, featuring four 845 valves per channel in parallel, driven by two amplification stages based on parallel ECC82 twin triodes. This configuration ensures a powerful, detailed, and dynamic musical performance, while maintaining low distortion and wide bandwidth. Each 845 valve has an independent DC heater supply to eliminate interference and ensure the highest signal purity. Bias for each tube is managed by a dedicated electronic circuit that constantly monitors and optimizes its operation, guaranteeing consistent performance over time.

Each monoblock features two 400-watt power transformers, built to the same high standards as the output transformers, using selected materials and 16 independent secondary windings. This intricate architecture allows each circuit to be powered separately, eliminating unwanted interactions and improving stability and reliability. The regulated 900V anode power supply is designed to behave like a battery system: thanks to MOSFET regulation and a dual capacitor bank, the result is a ripple-free current that enhances dynamics and sonic cleanliness.

The entire signal path is handled exclusively by valve components operating in pure Class A, while negative feedback is limited to about 8 dB and applied only to the cathode of the first tube—a choice made after extensive listening tests. Each section of the amplifier has its own dedicated board, for a total of eleven separate PCBs per monoblock. The massive, carefully crafted output transformers work in parallel to manage the energy from the four 845 tubes, ensuring precise control even with complex loads.

From a construction standpoint, nothing is left to chance. Premium materials such as non-inductive capacitors from Italcond and Siemens, pure ceramic tube sockets, extra-thick vetronite PCBs, and high-quality wiring all reflect the meticulous selection process behind each component. The dimensions of the circuit boards, the layout of the ventilation holes, and the separation of signal and ground paths, combined with a non-magnetic stainless-steel shielding, contribute to effective heat dissipation and reduced microphonics—key factors for long-term reliability and operational stability.

The design itself embodies a perfect balance of form and function. The stainless steel structure, non-magnetic metal knobs, and wooden inserts not only enhance the visual appeal but also help dampen vibrations, further preserving tonal purity. Even the power-on switch operates through a relay system that shortens the internal mains wiring, minimizing potential interference with the sensitive amplification circuits.

The Unison Research Reference is thus presented as an exceptional tube amplifier, conceived with no compromises. It delivers outstanding sonic performance and proudly represents the apex of the brand’s production—a perfect synthesis of engineering, passion, and Italian craftsmanship.

Technical Specifications:

• Type: mono valve power amplifier
• Output stage: double single-ended in parallel
• Class: pure A
• Valves: 4 x 845; 1 x ECC82; 1 x ECC83
• Output power: 80 watts
• Frequency response: 20 Hz – 30 kHz
• Feedback factor: 14 dB
• Output impedance: 4 Ohm; 8 Ohm
• Outputs: speaker terminals with bi-wiring capability
• Inputs: 1 x RCA; 1 x XLR
• Input impedance: 47 kOhm (RCA); 10 kOhm (XLR)
• Power consumption: approx. 400 VA
• Dimensions: 49 cm x 77.5 cm x H 28.5 cm
• Net weight: 70 kg; 155 lbs