ABSTRACT
The 2012 preamplifier has a flat gain stage after the RIAA phono section that can be switched from 0 to +20 dB in 5 dB steps. This was mainly aimed at accommodating the very wide range of Moving-coil (MC) cartridge sensitivities that exists. It is equally applicable to optimising the gain for Moving-magnet (MM) cartridges, but these vary much less in output. MC stage built around transistors T1-T4 and opamps IC1A and IC2A gives very low noise with the low impedances of moving-coil cartridges. It provides a fixed gain to its output of +30 dB. MM stage is a relatively conventional stage, except that it uses multiple polystyrene capacitors to obtain the required value and to improve RIAA accuracy. The switched-gain stage around IC7B allows every individual MC and MM cartridge on the market to receive the amount of gain required for optimal noise and headroom.
