A Transformer-Coupled Balanced Output for Solid-State Preamps

Longtime audioXpress contributor Gary Galo writes about a transformer-coupled balanced output circuit for solid-state preamps, usable with line-level signals. Exploring the differences between balanced interfaces and unbalanced interfaces - and finding things that we really want to be aware of, he then explains why he selected Jensen transformers for his own project.

Most consumer audio equipment is connected with unbalanced lines, using single-conductor shielded cables and RCA connectors. The short cable runs encountered in a domestic environment hardly ever cause audible noise, so audio manufacturers have traditionally found balanced lines unnecessary. In recent years, balanced connections on stereo preamps and power amplifiers have become more common. Most modern audio power amplifiers with balanced inputs have true differential input stages, so optimum performance is not dependent on signal symmetry at the balanced input. The issue is noise. Modern audio power amplifiers have lower inherent noise levels than their predecessors, and will perform best if they are fed from a balanced source.

This article was originally published in AudioXpress, February 2019.

Read the full article, now available here.