Pre-Out vs Line Out [Detailed Guide]

What does pre-out and line out mean? There are many terms used in audio, but these two can be really confusing especially if you’re new to audio. Pre-out and line out are two different types of audio signals found in most live sound setups.

They refer to an audio signal passing through a device such as a preamplifier, mixer or power amplifier. Although pre-out and line out are both signals that should go into your audio interface, they are both different in terms of their functionality and make.

Improper connection and usage of these signals can result in unwanted consequences. In this article, Audio Curious seeks to help you avoid such consequences by providing an in-depth explanation of the pre-out and line out threads to help you understand what they are, their differences, and how to use them.

What Do Pre-Out and Line out Mean?

Pre-out simply means before the output. This implies that the source device (for instance, the headphone amplifiers or DAC), will amplify the signal before sending it to your speakers or other audio equipment.

Line out, on the other hand, is a fixed voltage signal that allows connection with the external speakers. So, it simply sends your sound signal outside the mixer to be combined with other devices like headphones and speakers.

The Difference Between Pre-Out and Line Out

The primary difference between pre-out and line out is the path they take to get to your amplifier. Line out sends a copy of the output from an audio interface or mixer straight to the PA system, while pre-out provides a boosted version of this signal for use with monitors and speakers.

These two audio signals also differ in the following ways.

Unlike pre-outs, line out possesses a volume control knob that allows you to alter the level at which there will be amplification.

It’s also possible to use an external power source to power up your unit when using line out, something that’s impossible with pre-out. This emanates from the fact that line out possesses more components in its internal circuitry.

The pre-out system produces superior audio quality than line out because it’s physically and technically impossible to better what’s already of a higher performance than the previous generation.

A line output also has a higher resistance value than a pre-out connection as it contains many components between your headphone amp or DAC and your headphones/speakers.


Pre-out represents the first stage of your sound system. Pre generally stands for pre-out, which means the signal is amplified before it enters the power amp section of your piece of equipment. If you, for example, connect a device such as a headphone into a pre-out jack, you will hear only a preamp/clean signal from that source.

This comes in handy when you need to listen to just one source, such as a CD player or software on your computer or iPad, without having any sound effects from other audio devices connected to it. A pre amp’s job is to boost the signal from a low-level audio source like a CD player or turntable into a high enough voltage signal to drive speakers.

They have a great deal of control over the tone produced by your amplifier and are often used to shape the character of the sound. They are also balanced outputs which mean they will give you an output signal that can be easily connected to a device with balanced inputs such as studio, recorders, and live studio mixing boards without any hassle or rewiring.

Line Out

The line out jack is an unbalanced RCA type jack that’s usually yellow and white. It connects your PC right into your audio amplifier or powered speakers that you have at home.

They provide an unamplified electrical connection directly from an amplifier’s speaker outputs without any additional amplification. This allows users to connect their external amplifiers with their desired settings to control audio quality and power.

Pre-Out vs Line Out

Line out works through what’s called the line in port of your sound card, and what allows this to happen is that what goes from the line out of your computer runs through an audio splitter which then splits off a specific part of what was intended for the speakers then runs it into what they call ROAs.

They are typically used when you want each speaker on stage to have their monitor mix, then sent back through the main outputs at FOH (Front of house). Line outs also come in handy if you’re sending signals from multiple sources down long cable runs since they allow you to combine those signals.

Pre-Out Sub

The pre-out sub concept is a unique way of doing what all amplifiers do, amplify. A pre-out sub arrangement does this efficiently without the more complicated procedure of modern-day amplifiers.

The design concept behind pre-out subs deals with what happens inside an amplifier as it moves towards outputting sound to your speakers. Subwoofers are connected to the outputs labeled sub out just like any other speaker within an amplifier channel. They operate in precisely the same way as every other speaker, except the process for them starts even before what you hear comes out from your main speakers.

While what you would typically consider audible sound is entering your room at frequencies that we perceive as music, what are preamp input and the power amp in combination form what is generally referred to as a pre-out sub.

In this configuration, two channels of an amplifier are used to drive one speaker (the subwoofer). Typically only the highest channel is connected to the mono output jack on the receiver, but it can be helpful at times to connect both high and low channels.

Line In vs Line Out

The line level is a standardized means of representing analogue voltage levels. It is most commonly used to connect home stereos or other audio components to amplification devices such as integrated amplifiers/receivers and powered speakers.

These devices’ line-level input and output signals are 50 to 100 millivolts (mV) higher than line-level outputs and inputs designed for professional use. Devices intended for professional help may have either line-level or microphone preamplifier inputs.

The line-in jack on an electronic device is designed to accept line-level signals, while the line out jack usually provides a line out signal.

A line out is best used in conjunction with another type of connection cable, such as a pre-out amp, since it does not provide power for an amplifier or subwoofer. On the other hand, a line in cord can be plugged into any component without worry because it does not carry voltage.

While line-in jacks can typically accept line-level signals with high input impedance, line-out jacks provide a line output signal with the same low output impedance as microphone signals.

While line-in amplifiers work with speakers that have built-in amplifiers, line out amps work better with passive or unpowered speakers.

When connected to devices with the line in and line out capabilities, it is crucial to correctly connect these two jacks to avoid noise issues or disruption of intended signal flow. Connecting line in and line out incorrectly can lead to audio feedback or degradation of sound quality.

These problems often appear as crackling noises when an audio device is first turned on or when its volume control is moved rapidly from side to side.

Pre-Out Amp

The pre-out amp is located inside your head unit or amplifier, depending on how you set up your car audio. Its primary function is to amplify a low-level audio signal fed to the deck to be sent out as a high-level audio signal into head unit outputs.

Pre-out amp works basically like small power amplifiers. But instead of making the sound from an electrical signal directly, they process an electronic signal ( from the head unit) and send a more robust copy onto another piece of equipment( such as an amplifier).

Pre-Out Amp

These devices come fitted with control knobs that allow you to adjust the signal level inside them. They also have a place to put in extra wires for the input signal. The pre-out amp’s job is to amplify the output from your deck so that the pre-out can send it into another component like your subwoofer or your amp.

If you want your subs to get their power from pre-out, then pre-out will need some energy. This power usually comes from a spare battery wire or a fuse tap mounted under or behind the dash.


The difference between a pre-out and a line out can be challenging to decipher. But in the end, it’s all about how you want to use your audio equipment. If you’re looking for something portable that will work with any device, pre-out is the way to go, but if you need something permanent and robust, a line out cable will give you all you need.

Also Read: 2 Channel vs. 4 Channel amp: Which is Better?

Nonetheless, ensure you know how and when to use each of these cables before making any connections to avoid frustrations and damage by plugging something where it doesn’t belong.

Avatar for Jamie K. Martin

Jamie K. Martin holds a degree in Audio engineering from Husson University, Bangor. Martin spends most of his time testing and trying the technology he writes about to ensure that he provides first-hand information to our customers from all walks of life.

Leave a Comment