Simply 845 Walnut
Description
There are amplifiers with impressive numbers on the nameplate. And there are those that make you forget about the numbers after the first note. The Simply 845 is in the second category. The 845 single-ended amplifier with direct-heated triodes in pure class A, hand-assembled in Treviso, is Unison Research's second-rank integrated amplifier, second only to the legendary Absolute 845. But in the context of real musical experience, this difference in rank feels much smaller than the difference in cost between them.
The 845 tube — direct-heated, graphite anode, originating from pre-war radio technology — has long since achieved cult status in high-end hi-fi. It is known for its exceptional durability, low distortion, and that special sound character that single-ended amplifier enthusiasts call “live” or “analog” — not as a metaphor, but as a technical description of the low odd harmonics.
The Simply 845 uses two selected 845 tubes in the output stage and four selected ECC82/12AU7 tubes in the preamplifier stage. All stages — both preamplifier and output — operate in pure Class A without switching off any of the elements throughout the signal cycle. Output power is 23 watts per channel. Combined with sensitive acoustics from 90 dB and above, this is more than enough for any real listening experience.
In a tube single-ended amplifier, the output transformer is not just a component, but a defining element of the sound. Unison Research designs and manufactures the transformers for the Simply 845 exclusively in-house: each one is individually hand-made. The insulators between the windings are the thinnest Mylar and polypropylene: a choice of materials that minimizes parasitic capacitance and magnetic flux leakage. The result is an extended frequency range (20 Hz - 50 kHz) and very low harmonic distortion for a single-ended topology.
Feedback is 14 dB, a level chosen as a compromise between damping the output stage and preserving the lively, direct nature of the single-ended amplification.
All Simply 845 preamplification circuits are powered by stabilized linear power supplies, specially designed to minimize the penetration of network interference. All capacitors in the audio path are anti-inductive, with polypropylene dielectric. Volume control is Japanese ALPS RK27 with motorized drive. Four line inputs, outputs for tape recorder and subwoofer (stereo RCA). All connectors are gold-plated. Output impedance 6 Ohm: optimal matching with acoustics with a nominal impedance of 8 Ohm and higher.
Simply 845 weighs 30.5 kg - and this weight is felt as an argument even before the first turn on. A massive metal case with natural walnut or cherry inserts, chrome parts, openly installed 845 tubes with their characteristic large cylinders - this is an amplifier that shapes the space around itself. In the updated version, all connectors have been moved to the rear panel, which simplified the connection and made the front panel geometrically clean.
Simply 845 is revealed in full force with acoustics with a sensitivity of 90 dB and above - bookshelf or floor-standing speakers with an impedance of 6–16 Ohms. Opera Loudspeakers acoustics from the Callas and Classica lines are a natural and structurally related partner: both brands were born in the same city, in the same factory, with the same approach to materials and manual labor.
