Unison Research – Unico Due – Class-A Dynamic Integrated Amplifier

Unico Due is the latest amplifier from Unison Research. Unico Due benefits from Unison Research’s decades of experience in design and production technology. It maintains all the best qualities that made its predecessor a runaway success and introduces new and enhanced features.

CIRCUIT

The electronic circuitry of the Unico Due has been completely redesigned. While maintaining the qualities that made the Unico range such a legend in the audio industry, key improvements have been made that are nothing short of ground-breaking. Firstly, the power supply circuits have been enhanced thanks to a substantial increase in filter capacitance size and a new high quality shielded and encapsulated power transformer.

The heart of the preamplifier stage in based around two ECC83 double triodes (one per channel), configured as a gain stage followed by a cathode-follower. This circuit’s low output impedance efficiently drives the power stage that follows.

The Unico Due offers four inputs: three analog inputs and one USB digital input. The input selection uses sealed miniature relay switches to preserve the delicate low-level signals, whereas the volume regulation is based on an integrated high-precision, high performance resistor array followed by a set of digitally controllable analog switches capable of 120dB of attenuation with 0.5dB steps.

The power output stages are solid state and use a completely original combination of bipolar and MOSFET transistors. A sophisticated symmetrical BJT circuit is used that has moderate gain and very high intrinsic linearity, with separate feedback loops for AC and DC signals.

The power output stages of the Unico Due feature a non-switching bias control circuit which prevents the current in the output transistors from reaching zero. This greatly reduces distortion at low and very low listening levels and guarantees the highest sound transparency in any condition.

To improve performance further, Unison added regulated power supplies not only when it was absolutely necessary, but also in any part of the circuit where this would bring sonic improvements over using simple filtering. In the Unico Due there are no less than ten stabilized power supplies with output voltages ranging from 15V for low signal operational amplifiers to the 300V required by the valves in the preamplifier stage.

Particular attention was paid to the output stage power supply. Considering the high value, impulsive, almost intractable nature of the current that the power stage has to handle, Unison decided to adopt a bold solution: large-value, high-quality capacitor banks. The supply tracks on the PCB are generously sized and the ground return tracks have been designed with extreme care. The engineers at Unison Research embraced these challenges and solved them without compromising on quality and performance. The final result is a design where almost 25% of the entire surface of all the PCBs in the Unico Due is dedicated to supplying power to the output devices.

The same meticulous attention was paid to managing the low-level audio signal. Starting with the gold-plated input connectors, the speaker sockets are also gold-plated, robust, versatile, and completely insulated according to the latest requirements. Furthermore, the audio signal is fed through circuitry using the available, highest quality components: high-precision sealed micro-relay switches, carefully selected Mundorf capacitors, low tolerance metal film resistors, ceramic tube sockets with gold contacts, and much more.

POWER PROTECTION

Unico Due is equipped with a sophisticated microprocessor-controlled system that monitors its power output. In case the power output is high over an excessively long time, Unico Due gradually decreases the volume level to a more sustainable level to protect the power devices.

FEATURES:

The Unico Due aims to satisfy even the most demanding users and offers the following features:

Three line inputs, of which one can be configured to become a phono input after easy installation of an internal phono stage module which can accept any type of turntable cartridge.
One USB input to the Unico Due’s internal DSD 128 bit DAC.
One direct analogue line output from the Unico Due’s internal DAC, which allows it to be used as a stand-alone DAC.
A low impedance subwoofer output (SUB) with variable output level from the preamp for connection to an active subwoofer.
AV input that allows the Unico Due to be connected to a home theatre system: pressing the “push” button on remote control, the Unico Due will automatically select the chosen channel at a user-configured volume level.
Dynamic Class A power amplifier biasing where the power transistors never turn off completely. This provides excellent sound results even at low volume.