Self on Audio, 3rd Edition

Chapter 16Preamplifier 2012

Part 3: level indicator, source selector, power supply (Elektor, June 2012)

This is the third and final article on Preamplifier 2012, covering the level indication circuitry, the input selection system, and the power supply.

The Log Law Level LED, or LLLL, was thought up to help with the correct setup of phono input with switched gain options. It is, to the best of my knowledge, a new idea. A single LED level driven by a comparator typically goes from fully off to fully on for less than a 2 dB change in level when measuring actual music rather than steady sinewaves. The LLLL also uses a comparator to drive the indicating LED hard on or hard off, but before that is a simple log-converter so that the level range from ...