Self on Audio, 2nd Edition

4

Design of moving-coil head amplifiers

For many years moving-coil head amps were exotic devices of highly specialised design. They were usually all-discrete, to minimise noise, and because of this, and the very low feedback impedances to be driven, linearity was poor, and only acceptable because the signal levels were so low.

This design is a hybrid discrete/op-amp configuration, which gives very low distortion even at signal levels monstrously above the normal operating conditions. It sidesteps several problems by having much more gain than is normally required; this would normally be a very bad move, severely curtailing headroom, but here it works as it can be assumed that the MC amp is always followed by a moving-magnet disc stage with substantial ...