Unison Research Unico 90Unison Research Unico 90 Two stages. Nothing more. The Unico 90 was designed around a simple and disciplined premise: every stage added to an amplifier circuit introduces its own distortion, and as stages compound, the distortion structure becomes increasingly complex. The engineering response to this has historically been global negative feedback a corrective loop that reduces measurable distortion at the expense of phase accuracy and transient

Unison Research Unico 90

Two stages. Nothing more. The Unico 90 was designed around a simple and disciplined premise: every stage added to an amplifier circuit introduces its own distortion, and as stages compound, the distortion structure becomes increasingly complex. The engineering response to this has historically been global negative feedback — a corrective loop that reduces measurable distortion at the expense of phase accuracy and transient integrity. The Unico 90 addresses the problem differently: use the minimum number of stages required to do the job correctly, implement them with great care, and accept no corrective loops.

The Circuit

Stage one: ECC83 operating in pure Class A. This is the input stage — the point where the signal is at its smallest and most vulnerable, where the character of the amplifier is established before any gain is applied. The ECC83 is a high-gain, low-noise triode, and in Class A it operates at its most linear.

Stage two: HexFET output devices, directly coupled to the tube stage. No coupling capacitors between the tube and the output stage — those capacitors are convenient for bias management but they introduce colorations and bandwidth limitations that a direct-coupled circuit avoids. The HexFET devices provide the current capability and power that speakers require.

Zero global negative feedback. The consequence of that decision is that the amplifier's measured harmonic distortion is higher than a feedback-corrected design would show. The sonic consequence is that the distortion that remains is lower-order and musically benign, and the phase accuracy and transient response that feedback compromises are preserved.

Press Recognition

The Unico 90 has been reviewed by Hi-Fi+, Hifi News, and Stereophile. It holds a consistent position in recommended component lists and has been cited as a reference point for what hybrid amplification should achieve in its price range.

Specifications

• Output power: 90 watts per channel
• Input stage: ECC83, Class A
• Output stage: HexFET, directly coupled
• Feedback: Zero global negative feedback
• Origin: Handcrafted in Italy

Authorized Unison Research dealer. Questions about how the Unico 90 compares to the Unico 150 or whether it's the right match for your speakers? Reach out.