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Unison Unico CD

Unico CD is an integral part of the Unico range, both in appearance and in electronic design. It employs leading-edge technology and features some of the latest and best components, including D-to-A conversion chipsets from Crystal and a microprocessor from Philips which takes care of disc reading and information display functions. All the necessary information is shown on a large 8192-pixel screen capable of both text and picture display. The screen is back-lit and has fully automatic brightness adjustment which adapts to the ambient lighting to provide ease of reading at all light levels.

The transport chosen is a high-quality CD-Rom mech normally used in computers. The motors incorporated in the transport are of the low-vibration, brushless, asynchronous type. The laser has a glass lens, which is superior to the plastic lenses used in most CD players. The guides and supports for the moving parts of the tray are lapped steel (not plastic), and the output signal from this transport is an S/PDIF. As an added bonus this mech is mounted on a rubber suspension to reduce the possibility of vibration affecting the reading capability of the laser diode.

Digital signal processing is carried out first by a CRYSTAL CS8414 chip which provides clock-jitter reduction and correction and control of the audio data. Next follows the (optional) CRYSTAL CS8420 chip which takes care of oversampling at 96kHz, with a clock at 24.576 MHz. The output from this chip is fed to the CRYSTAL CS9342 converter which has a maximum capability of 24 bit/192kHz.
The signal is filtered by a passive network and sent to a valve preamp stage which operates in pure Class-A using 1 x ECC82 double triode for each channel. Audio output signals are provided in both balanced and low-impedance unbalanced (>100 Ohms) mode. On the rear panel there is provision for a digital input and output, in the optional version with oversampling.

All the electronic circuits are fed from one large, low-flux power transformer designed specially by Unison Research for this project. 5 separate stabilized power supply stages are used, of which the one providing anode voltage to the valves is a power MOSFET stage.

Input stage
Double triode ECC82 configured in a first Pure Triode Input Stage followed by a second triode stage with Bias Active Control. Anode voltage and heater current (dc) are stabilised.
Output stage
Improved Dynamic Class A Symmetrical Stage employing a Power MOSFET Complementary Pair
Damping factor
> 50
Feedback factor
8 dB
Amplifier overdrive
Overdrive indicated for THD > 1%