Rega AOS MC Phono Pre-Amp

Pure Analogue

The AOS is a two stage “all analogue amplifier” with no digital control circuitry. The fully aluminium case screens the internal circuit from any stray RFI signals. Our designers have avoided including any unnecessary components or circuits that may degrade the signal path. The AOS incorporates many innovative design ideas including a self-adjusting servo control which compensates for any variations in ambient or operating temperature.

The AOS utilises parallel connected, low noise FETs (Field Effect Transistors) configured as a compound pair. The use of FET transistors ensures there is no bias current flowing in the cartridge coil so as not to upset the delicate magnetic geometry of the cartridge. The MC input has the provision for selecting resistive input loading of 70 Ω to 400 Ω and capacitive loading of 1000 pF to 4300 pF. The input sensitivity can be changed by 6 dB via the back panel. An automatic standby feature has also been added which puts the unit to sleep after a period of no signal. This can be deactivated via dip switches located on the rear panel.

First Stage

The first stage is a symmetrical, complementary class A amplifier, using Linear Systems ultra-low noise FET (Field Effect Transistor) transistors. The use of FET transistors ensures there is no bias current flowing in the cartridge coil so as not to upset the delicate magnetic geometry of the cartridge. The input circuit configuration also alleviates the use of any coupling components between the cartridge output and the input stage FET transistors, which would degrade the sound. The complementary ultra-low noise FET transistors are carefully graded and matched for optimum performance.

This stage drives the passive high-frequency part of the RIAA equalisation stage. The complementary ultra-low noise FET transistors are carefully graded and matched for optimum performance.