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Performance Mahogany

  • Model: Performance Mahogany
  • Shipping Weight: 50kg

In its more than twenty years of history to date, Unison Research has produced not only separate pre- and power amplifiers but also many integrated amplifiers of both low and medium power output. Integration offers several advantages, not only for simplicity and practicality of use, but for the improvements to sound quality that can be obtained. An integrated amplifier requires less cabling than its separate counterparts, both for mains supply and for interconnects, and that provides a worthwhile saving in cost. More importantly, cabling can have an undesirable effect on timbre, soundstage and dynamics.
The design of an integrated amplifier is therefore more critical and complex than that of a separate pre-power combination. The design of a single-chassis design requires great care in order to isolate the sensitive gain stages from interference from the power supply or output stage.
Our experience with integrated amplifiers has enabled us to produce some very successful designs over the years, some of which are revered as valuable classics such as the widely renowned Absolute 845.
To satisfy the constant and pressing requests from our customers worldwide, Unison Research has decided to bring back into production one of its best known classic pieces, the Performance.
We decided at the outset to introduce some improvements and important modifications to this classic integrated amplifier. First and foremost, the power output goes up from 24 watts to more than 40 watts per channel thanks to the use of six KT88 valves in the output stage. While the new Performance remains faithful to the winning look of the original–regarded by many as an object of rare and pleasing elegance–the few changes that have been made are due to functional necessity such as the insertion of large thermic radiators on both sides of the chassis as well as the cover that uses two stainless steel screens. This material is non-magnetic with low heat conduction, which prevents the heat generated by six KT-88s from reaching the circuits positioned below. This feature enhances both the stability and the overall reliability of the Performance.
As with all high-quality integrated amplifiers, the Performance is laid out in dual-mono configuration. Within the single chassis are two identical but fully independent amplifiers. This avoids any possibility of interference, whether electrical or electronic, between the two channels. Valves are used for all the amplification stages, and all of the valves operate in pure Class-A mode.
From the very beginning, Unison Research has been dedicated to the design, development and manufacture of output transformers. We are convinced that these components (which very few amplifier manufacturers in the world are able to design and build themselves) are largely responsible for determining the ultimate quality of the sound of a valve amplifier. Thanks to these special transformers, it has been possible to design an output stage for the Performance using three KT88 valves per channel in a parallel single-ended ultra-linear configuration. Ultra-linear operation is possible thanks to a particular adaptation of the output transformer which enables it to see the KT88 tetrodes as if they were triodes.
Pre-amplification and power stage drivers are based entirely upon triodes with the use of ECC83 and ECC82 valves. With these valves it is possible to obtain excellent linearity and a virtual absence of odd order harmonic distortion. Both these stages are designed with triodes in parallel and use automatic biasing. This allows the output impedance of the two circuits to be usefully reduced, while total harmonic distortion is also reduced and the signal-to-noise ratio is increased.
Particular attention in the design phase was given to the output stage which, as stated previously, consists of three KT-88s in parallel. The use of output valves in parallel provides excellent sonic results, but their use is critical in that they impose the need for rigorous selection and matching of the valves. These problems are only partly resolved by the use of selected valves since over time the characteristics of the valves tend to alter in a non-uniform manner, which could lead to unbalanced output, power loss and an increase in harmonic distortion. Having fully evaluated all aspects of valve behavior over time, a special and original circuit has been developed in our laboratory which neatly solves the problem by constantly checking each valve for variations in performance and adjusting the bias accordingly. With this circuit the amplifier is able to maintain peak performance, even after years of use. As an added bonus, the circuit enables warm-up time from switch-on–necessary for all valve amplifiers–to be greatly reduced.
The same care and attention taken over the amplifying stages has been given to the power supply. The power transformers of the Performance are not ordinary transformers. They have been designed and made with the same criteria as the output transformers, not only for reliability but also to ensure ideal conditions of operation for the whole amplifier. It is useful to remember that all the energy flowing to the loudspeakers comes from the power transformers. These are provided with a large number of secondary windings in order to furnish the precise requirements of each group of components while reducing the interaction between them. Preamp and driver valve filaments are supplied with direct current. Power valves, on the other hand, require heating of a different order and are therefore supplied with alternating current, each from a separate winding and independent balancing network. In this way problems associated with high current rectification are avoided, independent bias of the three output valves is maintained and the efficiency of the amplifier is thereby improved.
Anode tension for an amplifier would ideally be supplied by a battery, but obviously this is not possible for a number of reasons such as cost, life-expectancy, size, weight and so on. We spent some considerable time studying this problem to determine if it would be possible to provide anode power supply close to what would be provided from a theoretical bank of batteries, and after much experimentation we were able to perfect a valid solution. To remain faithful to the philosophy of valves, each power supply is made up of a single supply to each valve, a power MOSFET. This component is used as a separation stage between rectified voltage at the transformer secondary and the supply voltage at the output stage, the anode voltage. Its purpose is to regulate the load current of the filter capacitors, which therefore is perfectly continuous and not, as in normal circuit designs, impulsive. One other significant advantage is that the output capacity of the power supply is called upon to furnish only the component required in signal amplification (having excluded those associated with rectification) which results in an increase in the total effective size of the filter capacitors. The anode supply developed for Performance may therefore be considered as having an output capacity far greater than a normal power supply, and moreover capable of behaving in a way which is akin to that of a battery.
The Performance is supplied with an infra-red remote control for analogue control of volume via an ALPS motorized potentiometer of the prestigious RK27 series, as well as for control of input selection. The chosen input is indicated at switch-on by illumination of its associated LED on the front panel. A tape monitor switch is also provided. Input selection and tape monitor operation are carried out by gold-plated and hermetically-sealed relays to reduce to the signal path to a minimum, thereby avoiding the possibility of signal degradation and maintaining good reliability over time.
Six large gold-plated loudspeaker terminals are provided for each channel, capable of accepting all types of cable termination in either single or bi-wiring for either 4 or 8 ohm loads. Input sockets are also of high quality and gold-plated.
The on/off switch on the front panel does not act directly on the incoming AC mains but instead commands a pair of power relays, one for each channel. These relays are placed close to the mains transformers allowing AC mains cabling–and hence the possibility of mains induced disturbance–to be kept to an absolute minimum.
The rear panel hosts an output socket for connection to the Unison Research Simply Phono, thereby allowing a phono stage of suitable quality to be used.
Nothing has been left to chance in the design and realization of the Performance. For example, the control knobs are machined from solid non-magnetic stainless steel. Thanks to their weight, mass and balance, they provide smooth and precise control when operated manually. The wooden parts–which have an obvious advantage in terms of appearance—have a less obvious but equally important purpose of damping any resonances which may otherwise be induced in the metal chassis. Thanks to this structural damping, the valves themselves (which like all vacuum tube devices are susceptible to microphony) are much less liable to generate unwanted resonance-related effects. For the best reliability and long-term musical quality, all the components used in the Performance have been chosen with care–from the non-inductive resistors to the filter capacitors (from Italy’s Italcond and Germany’s Siemens) and the pure ceramic valve bases to the printed vetronite circuit boards.
The dimensions of the PCBs and the placement of the vents for air circulation have been accurately designed to avoid the overheating of internal components, which is beneficial to long-term amplifier reliability. The PCBs, which are independent for each channel, are made with great care in respect to the layout of signal paths, power supply tracks and even the dimensions of the tracks themselves. Star grounding is used, and the signal tracks are widely separated–all in the quest for the cleanest passage for the audio signal possible.
All of this comes from more than two decades of experience at Unison Research, which guarantees that the new Performance is indeed a superb integrated amplifier, the pride of our current production.

Available in cherry or mahogany finish

◦Type: Dual mono Stereo Integrated Valve Amplifier
◦Output Stage: single ended parallel ultralinare A class
◦Output Power: 45 W / channel
◦Inputs: 4 line, 1 tape
◦Input Impedance: 47 kOhm
◦Outputs: 1 tape, loudspeakers bi-wiring
◦Output Impedance: 4 – 8 ohm
◦Feedback factor: 16 dB
◦Frequency Response: 20 Hz – 30 kHz
◦Valves: 6 x 6550/KT88 , 2 x ECC82 , 2 x ECC83
◦Remote Control: IR inputs and volume
◦Power Consumption: 500VA max
◦Dimension: 60cm x 48cm x 23,5 cm.
◦Net Weight:50 Kg


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