Preouts

Preouts, short for preamplifier outputs, are line-level audio outputs that carry the signal from the preamplifier section of a stereo or AV device to external equipment. They are distinct from the device's main speaker outputs, which feed power amplifiers and loudspeakers. In practice, pre-outs allow users to add external amplification, signal processors, or subwoofers without relying on the device’s built-in amps.

Most pre-out jacks are RCA connectors labeled left and right; some equipment provides dedicated subwoofer pre-outs or balanced XLR connections. The signal is a controlled, line-level output intended to be fed into another amplifier, a processor, or a subwoofer’s input. The precise electrical characteristics, including whether the level follows the device’s volume control, depend on the model.

The level and behavior of pre-outs vary by device. On many receivers, the pre-out level tracks the main volume control, so increasing the device’s volume raises the level sent to external gear; on others, the pre-out may be fixed at a set level. Checking the manual helps determine how to set levels and how the volume control affects the signal.

Common applications include bi-amping with a separate power amplifier, routing the signal through external processors or equalizers, or feeding a powered subwoofer via a dedicated pre-out. Pre-outs provide flexibility for expanding or upgrading an audio system without replacing built-in amplification, and they are a standard feature on many home audio receivers and processors. See also: line out, main out, subwoofer out, LFE out.