The Rega Ios is a four stage, all symmetrical amplifier. The first stage uses a 1:10 step-up transformer which can be optimised to the cartridge by the selection of the correct loading and Zobel DC resistance correction network connected across the MC transformer secondary.
The second stage is a symmetrical, compound pair class A amplifier, using paralleled low noise Hitachi transistors in the input stage. This drives the passive high frequency part of the RIAA (Record Industry Association of America) equalization stage.
The third stage is a symmetrical class ‘A’ differential amplifier with a common base driver stage; this is also used as the active amplifier in the low frequency part of the RIAA equalization stage. The fourth stage is the active filter. This configuration uses the same circuit as found in the second stage. The filter element uses a very high bandwidth operational amplifier.
The power supply is a symmetrical, discrete tracking power supply using fast diodes and a low noise voltage reference. Each stage has its own localised power supply and LED referenced current generators. Very high quality polypropylene capacitors have been used in the signal path. 1% tolerance polypropylene capacitors are used in the RIAA EQ stages and audio grade capacitors are used in the rest of the circuit. We hope that you enjoy this product as much as we have enjoyed creating it.