Linestages

Linestage refers to the portion of an audio preamplifier that handles line-level signals from source components. Its primary functions are to provide appropriate gain, impedance matching, and buffering between sources such as CD players, DACs, and streaming devices, and the power amplifier, while preserving signal integrity across the audible bandwidth.

Line-level sources typically output nominal voltages around 1 V or less. A linestage presents a high input impedance to avoid loading the source and a low output impedance to drive the next stage, whether that is another component or a power amplifier. Outputs are commonly provided via RCA and/or XLR connectors, with some designs offering balanced operation for reduced noise and better common-mode rejection.

Linestages can be implemented as active or passive designs. Active linestages use gain stages built with tubes or solid-state devices to amplify the signal, sometimes offering additional features such as tone controls or source switching. Tube-based linestages are often described as imparting a particular sonic character, while solid-state designs are typically valued for transparency and low noise. Passive linestages rely on resistive networks for volume control and buffering, aiming to minimize active circuitry in the signal path, though they may require careful source impedance matching to preserve dynamics.

Phono preamps perform a separate function, applying RIAA equalization to turntable signals; linestages generally do not include this equalization.

In practice, linestages appear as part of integrated preamplifiers or as standalone units. Performance characteristics of interest include gain accuracy, noise, distortion, channel balance, and the ability to drive downstream equipment without compromising signal integrity.