Unison Research REFERENCE PRE Tube Preamplifier at Vinyl Sound Buffalo, NY USA

The REFERENCE PRE is a dual mono, three-chassis tube preamplifier from Unison Research (Treviso, Italy), available at Vinyl Sound in Buffalo, NY, USA. Designed as the purpose-matched partner to the REFERENCE TUBE monoblock power amplifiers, the REFERENCE PRE operates in pure Class A and uses a tube complement of two 300B, two ECC82, four ECC83, and six 6C45P valves across its three chassis -- one audio chassis and a separate power supply. Its four line inputs (including two balanced XLR), two phono inputs, and active tape and subwoofer outputs provide comprehensive system integration, while its 500-ohm output impedance ensures compatibility with virtually any power amplifier input stage. Remote switch-on for the REFERENCE TUBE monoblock pair is built in.

Three-Chassis Pure Class A Architecture

The three-chassis design of the REFERENCE PRE is a fundamental statement about power supply isolation. By housing the mains transformer, rectification, and regulation in a physically separate enclosure from the audio circuit, Unison Research eliminates the primary path by which power supply noise couples into the signal stage. The 300B directly-heated triodes serve as the output stage of the preamplifier -- an unusual and demanding choice for a line-stage application, given the 300B's heater current and the challenge of achieving low noise with a DHT tube in a high-gain, low-level circuit. Six 6C45P tubes, a high-transconductance Russian-designed triode, handle the initial gain and driver stages, while ECC82 and ECC83 provide buffering and phase-splitting duties. The entire circuit operates in pure Class A throughout.

Connectivity and System Integration

The REFERENCE PRE's input complement covers both balanced and unbalanced line sources: four line inputs include two XLR balanced and two unbalanced RCA, with input impedances set for optimal compatibility with studio-standard sources. Two phono inputs are provided -- one unbalanced and one balanced -- covering both moving-magnet and moving-coil cartridge configurations when used with the appropriate load settings. An active tape output, an active subwoofer output, and two remote power switch-on circuits for the REFERENCE TUBE monoblock pair complete the connectivity specification. The output impedance of 500 ohms is low enough to drive long interconnect cables without high-frequency rolloff, ensuring system flexibility.

Key Features

• 300B Output Tubes: Directly-heated triodes in the output stage of the preamplifier, a premium engineering choice associated with the highest-resolution Class A line-stage designs.
• Three-Chassis Construction: Separate audio and power supply chassis eliminate mains noise coupling into the signal path at the most fundamental level.
• Pure Class A Operation: All gain and output stages operate in pure Class A throughout the signal chain.
• Dual Phono Inputs: One unbalanced and one balanced phono input accommodate a wide range of cartridge and step-up transformer configurations.
• Two Balanced XLR Line Inputs: Balanced inputs compatible with studio sources, balanced DACs, and balanced-output CD transports.
• Remote Switch-On for REFERENCE TUBE: Built-in relay switching for simultaneous power-on of up to two REFERENCE TUBE monoblock amplifiers.
• 500-Ohm Output Impedance: Low source impedance drives long cable runs without frequency response degradation.

Technical Specifications

Frequently Asked Questions

What is the Unison Research REFERENCE PRE?

The Unison Research REFERENCE PRE is a dual mono, three-chassis pure Class A tube preamplifier from Treviso, Italy, using 300B, ECC82, ECC83, and 6C45P tubes. It provides four line inputs (two balanced), two phono inputs, an active tape output, an active subwoofer output, and built-in remote switch-on for the REFERENCE TUBE monoblock amplifiers. Its output impedance is 500 ohms.

How does the REFERENCE PRE compare to the Unison Research Simply 845 integrated amplifier's built-in preamplifier stage?

The REFERENCE PRE is a dedicated three-chassis preamplifier using 300B output triodes and 6C45P driver tubes in pure Class A, designed for the most demanding reference system configurations. The Simply 845 integrates both preamplifier and power amplifier in a single chassis using ECC82 tubes for its preamplifier stage -- a more compact, convenient solution at lower cost and complexity. The REFERENCE PRE offers a significantly more elaborate circuit, greater connectivity (including two balanced phono inputs and XLR line inputs), complete power supply isolation, and the ability to drive any power amplifier independently of an integrated amplifier constraint.

What is the 6C45P tube used in the REFERENCE PRE?

The 6C45P is a high-transconductance triode of Russian origin, originally developed for instrumentation and measurement applications. In audio preamplifier circuits, its high transconductance -- typically three to five times that of a standard ECC82 -- enables voltage gain stages of lower output impedance and reduced noise. In the REFERENCE PRE, Unison Research deploys six 6C45P tubes in the initial gain and driver stages, taking advantage of the tube's linearity at low signal levels to establish a low-noise gain structure ahead of the 300B output stage.

Can the REFERENCE PRE drive amplifiers other than the REFERENCE TUBE?

Yes. The REFERENCE PRE's 500-ohm output impedance is compatible with any power amplifier or integrated amplifier with an input impedance of 5k ohms or higher -- which encompasses virtually every high-end power amplifier currently available. The balanced XLR outputs (derived from the balanced line inputs and phono inputs) allow connection to fully balanced power amplifiers. The built-in remote switch-on circuits are specifically wired for the REFERENCE TUBE monoblock pair but do not restrict the preamplifier's use with other amplifiers.

Where can I buy the Unison Research REFERENCE PRE in Buffalo, NY or the USA?

The Unison Research REFERENCE PRE tube preamplifier is available at Vinyl Sound in Buffalo, NY, USA. Vinyl Sound is an authorized Unison Research dealer serving customers across western New York and the wider United States. Contact the Vinyl Sound team for current availability and to arrange an in-store system demonstration with the REFERENCE TUBE monoblock pair.