what is a pre out on an amplifier

3 min read 25-12-2024

A pre-out, short for preamplifier output, is a crucial feature on many amplifiers, especially those designed for home audio setups or car audio systems with external processing. This article will delve into what a pre-out is, its purpose, and how it enhances your audio experience. Understanding pre-outs is key to optimizing your sound system's performance.

What is a Pre-Out?

A pre-out is essentially a signal output that taps into the amplifier's preamplifier stage. This stage is responsible for boosting the weak signal from your source (CD player, turntable, etc.) to a level suitable for amplification. Unlike speaker outputs, pre-outs send an unamplified signal. Think of it as a "copy" of the pre-amplified signal, before the power stage boosts it to drive your speakers.

This unamplified signal is crucial for connecting external audio processing equipment. This equipment often requires a clean, unamplified input signal to process.

Why Use Pre-Outs?

The primary reason for using pre-outs is to integrate external audio processing units, improving overall sound quality and flexibility. These units might include:

Graphic Equalizers (EQs): These allow you to adjust the frequency balance of your audio, tailoring it to your preferences or correcting for room acoustics.
Subwoofer Amplifiers: A dedicated subwoofer amp can provide more power and control over low-frequency sounds, improving bass response.
Digital Signal Processors (DSPs): DSPs offer advanced signal processing capabilities like time alignment, crossovers, and more nuanced EQ adjustments. They're a very popular choice for home theater systems and car audio enthusiasts.
External DACs (Digital-to-Analog Converters): If your amplifier's built-in DAC isn't top-notch, a higher-quality external DAC can significantly improve sound quality.

How Pre-Outs Work

The signal from your audio source passes through the preamplifier stage of your main amplifier. The pre-out taps into this stage, creating a copy of the signal before it reaches the power amplifier stage. This unamplified signal is then sent to your external processing unit. The processed signal is then sent to the power amp. The power amplifier stage is then used to drive your speakers, or the final signal is sent to your speakers depending on the device connected to the pre-out.

Pre-Outs vs. Speaker Outputs

It's crucial to understand the difference between pre-outs and speaker outputs. Speaker outputs deliver a powered signal—the signal after it's been amplified to drive your speakers. Connecting external devices to speaker outputs could damage your equipment. They're designed to drive high-power speakers, not sensitive processing units. Pre-outs, on the other hand, provide an unamplified signal safe for connecting external processors.

Connecting External Devices to Pre-Outs

Connecting external devices to pre-outs is usually straightforward. Most pre-outs use RCA (phono) connectors. You'll need an RCA cable to connect the pre-out on your amplifier to the input of your external device. Always consult your amplifier and external device manuals for specific instructions and connection diagrams.

Choosing an Amplifier with Pre-Outs

If you plan on using external audio processing equipment, it's vital to choose an amplifier with pre-outs. The availability of pre-outs often reflects the amplifier’s overall quality and versatility. Higher-end amplifiers frequently include multiple pre-outs, allowing you to connect several processing units simultaneously.

Conclusion

Pre-outs are a valuable feature that opens up a world of possibilities for improving your sound system. By enabling the integration of external processing units, pre-outs allow for customized sound tuning, improved clarity, and enhanced overall audio quality. Understanding what a pre-out is and how it works is essential for anyone looking to build or upgrade a sophisticated audio system. If you’re serious about high-quality audio, investing in an amplifier with pre-outs is a wise decision.