Audio Signal Interfaces and System Earthing

Although the subject has a "black art" reputation, this tutorial replaces myth and hype with insight and knowledge, revealing the true causes of system noise and earth loops. Although safety must be the top priority, some widely used "cures" are both illegal and deadly. While both balanced and unbalanced interfaces are vulnerable to noise coupling, the unbalanced interface is exquisitely so due to an intrinsic problem. Because balanced interfaces are widely misunderstood, their near-perfect noise rejection is severely degraded in most real-world systems. Some equipment has a built-in noise problem due to an innocent design error. A simple, no-test-equipment, troubleshooting method can pinpoint the location and cause of system noise. Signal-path earth isolators solve the fundamental noise coupling problems. Unbalanced-to-balanced connections, RF interference, and mains treatments (such as technical power, balanced power, isolation transformers and surge suppressors) are also discussed. The InGenius IC and a new, balanced RCA connector are also described.