Unison Research Unico 150

150 Watts with a Tube Heart

Most hybrid amplifiers add tubes at the input stage as a tonal corrective — a way to warm up a solid-state circuit that might otherwise be clinically neutral. The Unico 150 was not designed that way. The two tube stages here — ECC83 at the input and 6H30 at the driver — are the circuit's sonic foundation, operating in pure Class A, directly coupled to a HexFET output stage that is powerful enough to drive virtually any speaker made. The result is not a solid-state amplifier with a tube flavor. It's a tube amplifier with solid-state authority.

Unison Research built the Unico 150 to a standard they describe as almost impossible to achieve with conventional technologies — meaning the kind of linearity across the full power range that most hybrid designs don't get close to. The measured distortion figures make the point plainly: less than 0.005% at 1 watt, less than 0.002% at 10 watts, less than 0.003% at 100 watts, less than 0.002% from 20Hz to 20kHz at 150 watts. Those numbers don't degrade as power increases. They stay flat. That is not a typical result.

The Three-Stage Circuit

The Unico 150 uses what Unison Research calls a three-stage counter-zero topology — specifically chosen for higher-power integrated amplifiers where the gain requirements make a two-stage circuit less effective. The philosophy behind both approaches is the same: as few stages as possible, each one doing its job without redundancy, without thermal compensation stages that introduce their own distortion, and without the global feedback loops that most amplifiers rely on to paper over non-linearity in the output stage.

Zero global feedback. Sixteen dB of local feedback within the output stage only. The direct coupling between the tube stages and the HexFET output is what makes the elimination of thermal compensation possible — the linearity of the tube stages carries through directly, and the output stage inherits it rather than requiring correction. This is an unusual design decision that requires confidence in the tube stages to get right. Unison Research ran thousands of simulations and built dozens of prototypes before arriving at the Unico 150. The distortion figures suggest they got it right.

Each channel has its own 400VA toroidal transformer — dual mono throughout — and the HexFET devices are specified to handle up to 1200 watts each, running at 70% of maximum capacity under normal operation. That margin is not about caution. It's about the character of devices operating well within their limits: lower thermal stress, more consistent behavior across the power range, longer service life.

The Preamplifier Section

The preamplifier section is fully passive — no active gain stage between the input and the tube driver. This was a deliberate constraint: adding an active preamp stage would have increased the circuit count, which Unison Research was not willing to do. Input switching uses purely mechanical miniature relays armored and placed directly behind the input sockets, with unused terminal contacts deflected to ground through appropriate resistors to eliminate capacitive coupling through the switch contacts.

The balanced XLR inputs use transformers rather than electronic balancing — a more expensive approach that provides true differential signal transmission, minimal differential impedance, and galvanic isolation that electronic balancing cannot match. Input selection is controlled by the remote, and a bypass input allows the Unico 150 to function as a pure power amplifier in a home theater or multi-amplifier system.

What It Sounds Like

What Hi-Fi described the Unico 150 as something of a powerhouse — drawn first to its scale and authority, the sense of headroom and ease at volume, and then to something they didn't expect: a large dose of fun. Muscular, energetic, with a fluid midrange and strong dynamics that made everything from large-scale orchestral works to uptempo hip-hop equally convincing. Their conclusion: immensely likeable, big-hearted, and — importantly — not the kind of amplifier that sacrifices enjoyment in the pursuit of refinement.

Stereo Times' David Abramson spent extended time with the 150 and called it easily among the very best and most versatile amplifiers he'd had at home. Quiet, refined, powerful, dynamic, and tonally beautiful. He also confirmed, helpfully, that it is extremely heavy and that once you find a spot for it, you should leave it there.

Pursuit Perfect System noted that the Unico 150 stays totally composed at big dynamic swings even at loud volumes, presenting music with a combination of sweetness and smoothness alongside genuine micro-detail retrieval. An amplifier designed for audiophiles to enjoy their whole music collection — which is a harder brief to meet than it sounds.

A Practical Note on Placement

The Unico 150 runs warm. The heatsinks are substantial and the ventilated top cover manages heat effectively, but this is a 550VA amplifier with serious output capability and it needs room to breathe. Leave space above and around it. It reaches nominal linearity almost immediately, with optimal performance in around ten minutes — not an amplifier that demands a lengthy warm-up ritual, but one that benefits from the first few minutes of operation before critical listening.

It is also 25 kilograms. Plan accordingly.

Press Recognition

What Hi-Fi reviewed the Unico 150 and described a muscular, energetic presentation with huge scale, strong dynamics, a refined and fluid midrange, and an energetic delivery that made listening genuinely fun. Their summary: immensely likeable, with a big-hearted presentation that stands out in a category where many competitors prioritize refinement over engagement.
Read the review

Stereo Times' David Abramson called the Unico 150 easily among the very best and most versatile amplifiers he had reviewed, describing it as quiet, refined, powerful, dynamic, and tonally beautiful.
Read the review

Pursuit Perfect System praised the Unico 150's composure under big dynamic swings and its ability to combine sweetness and smoothness with genuine detail retrieval — an amplifier designed for serious listening across all kinds of music.
Read the review

Specifications

• Type — Hybrid integrated amplifier, dual mono
• Output power — 150W × 2 @ 8Ω; 250W × 2 @ 4Ω
• Input stage — Pure Class A, ECC83 double triode totem pole
• Driver stage — Pure Class A, 6H30 double triode totem pole
• Output stage — Class AB, 8× Hexfet MOSFET
• Global feedback — 0 dB
• Local feedback — 16 dB
• THD — less than 0.005% @ 1W; less than 0.002% @ 10W; less than 0.003% @ 100W; less than 0.002% @ 150W (20Hz–20kHz)
• Output impedance — less than 0.4Ω (resistive across all audio frequencies)
• Frequency response — -1dB @ 12Hz and 45kHz; -3dB @ 6Hz and 80kHz
• Input impedance — 24kΩ / 100pF
• Input sensitivity — 860mV RMS
• Power supply — 400VA + 400VA toroidal transformers (dual mono)
• Inputs — 3× RCA unbalanced; 2× XLR balanced (transformer coupled); 1× RCA bypass
• Outputs — 4 + 4 binding posts (bi-wiring); 1× tape RCA; 1× subwoofer RCA (volume controlled)
• Power consumption — 550W at maximum power into 8Ω
• Dimensions — 43.5 × 44 × 18 cm (W × D × H)
• Weight — 25 kg
• Finish — Silver or black
• Origin — Handcrafted in Italy

Questions about how the Unico 150 compares to the Unico DM v2, or how it pairs with your speakers? We're happy to help you think it through.