Self on Audio, 3rd Edition

Chapter 1Advanced preamplifier design

A no-compromise circuit with noise gating (Wireless World, November 1976)

This was my first preamplifier design, conceived in 1975, the first year that I worked in the audio industry. The two gain-control solution to the dynamic-range problem was inspired by what was thought of as advanced industry practice at the time—notably in products by Radford and Cambridge Audio. I thought the rumble-gate concept was rather clever, but I seem to have been in a minority of one, as it was never even mentioned in the correspondence that followed. That was rather a disappointment.

The major part of the circuitry consisted of two discrete opamps with differential inputs, which performed the amplification and tone-control ...