What Are Preamp Outputs on the Car Stereo?




As an affiliate, ImproveCarAudio get small commissions for purchases made through links on this website from Amazon and other third parties.

The preamp is a shortened term for “preamplifier.” Although this is popular and we often hear “preamp,” many wonder what a preamp output actually is and what it is used for? Let’s find out.

Preamp outputs on a car stereo are low-level audio signals found on the back of the head unit and labeled as RCA connectors. Preamp outputs deliver low-voltage signals to external amplifiers, enabling users to enhance audio quality and customize their system with additional amplifiers, subwoofers, or other components. Providing a clean signal free of noise and distortion with a higher S/N ratio ensure optimal sound performance in vehicles.

Tip: If your radio has only two preamp outputs, and you want to connect a four-channel amplifier, the simplest way is to split the signal using a “Y” RCA splitter cable.

Enhancing your car’s audio involves understanding different car stereo features. Learn more about these features and how they can transform your driving experience with our comprehensive guide.

In the article below, I will explain some details about preamp outputs and clarify how to increase the number of preamp outputs from the car stereo.

What Are Preamp Outputs Used for in Car Radios?

In standard car stereo systems, preamp outputs are connected with amplifiers by RCA wires. This way, sound signal is transmitted from the radio’s preamp to the amplifier.

Preamp level outputs are audio outputs used to drive an amplifier, or other types of car audio element, like equalizer or crossover.

Preamp level outputs do not have enough current flow to drive speakers directly, and they have to be connected to the amplifying element of the car audio.

As you can see, preamp outputs are very similar to line-level outputs, like those on a CD player or an iPod. The main difference between the two types of output is the amount of voltage they produce.

How Many Preamp Outputs Do I Need in the Car Radio?

Generally, you need as many preamp outputs as you have channels in the amplifier. For example, if your amplifier has four channels, you need four preamp outputs.

Some radios will have only one set of preamp outputs, while others can have multiple pairs of outputs for front, rear, and subwoofer signals.

Also, some radios allow you to switch a low pass crossover for the rear outputs and convert them to a subwoofer output.

What Is the Difference Between Pre-out and Preamp Out?

Pre-out is an analog audio source that has already been amplified to line level. This means it can be connected directly to an external amplifier’s input without needing any extra equipment.

When using an RCA style output, the only limitation is that there must be enough voltage to drive the amplifier.

A preamplifier is a device that increases an audio signal from a source, such as a turntable or CD player, to make it strong enough for the amplifier. The preamp does this with electricity, making the sounds louder.

How to Use Preamp Outputs?

Preamp outputs are straightforward. All you have to do is connect the RCA wires and the same on the other sire with the amplifier or equalizer.

The one thing you need to pay close attention to when using preamp outputs is the output impedance of your source unit. If this is not high enough, it can cause damage to your amplifier or other car audio component.

Where Are Preamp Outputs on Car Stereo?

Preamp outputs are placed on the rear of a radio or CD receiver, allowing easy connection with standard RCQ wires.

Some car stereos have the preamp outputs on the front of them, so you can easily tap into them, but these radios look odd with all the wiring at the front.

Can I Add Preamp Outputs to the Car Radio?

Adding preamps to the existing ones on your car stereo is possible, but there are few things to consider before doing so.

  • The preamp output that you add must be amplified and tuned specifically for the speakers in the car. There is a higher risk of noise when tapping into current outputs, and any additional RCA line will reduce the signal strength.
  • Another thing to remember is that adding additional preamp outputs to existing ones will not create the effect of the extra channels. If your radio has two preamps and you add another two, you will end up having two left front (or rear) and two right channels.

If your car stereo does not have preamp outputs, or you need more, so for the best performance, you need to either replace the car radio with one that has more preamp outputs or, if you can’t do that, add an outboard preamp, for example, PAC LP7-4.

The outboard preamp is a small car audio signal converter that will transfer the hi signal from the stereo and send it further to the amplifier.

The addition of an outboard preamp is beneficial when you want more speakers in the future. Simply add another preamplifier for each set of outputs and connect all your amp channels using speaker-level inputs or a signal distribution block!

More output signals allow you better control over the sound quality and better signal distribution. With only one pair of preout cables, you will be able to connect your radio only with a two-channel amplifier.

Can I Split Preamp Outputs?

If your radio does not have enough preamp outputs, you can split them using a “Y” RCA splitter cable.

RCA Splitter, 2 Pack RCA Male to Dual RCA Female Y Splitter Cable Stereo to Mono Adapter, 8 Inches Gold Plated Audio Cable Cord RFAdapter for Subwoofer Speaker

Splitting will allow you to send the signal out for more channels, but it will also degrade the sound quality.

The same happens when it comes to the subwoofer. If you originally have two preamp outputs for the subwoofer, you can make a direct connection for two woofers, but if you would like to use four woofers, you’ll need to split these channels.

To do this, run “Y” RCA cables from the back of the deck and connect them to all inputs in the amplifier. This way, every channel in the amplifier will receive the signal.

Further Reading About Car Radio Features

If you like this post, there are a few more related to this topic that you may find interesting. If you do, click the link below and enjoy another article.

Which Radio Fits My Car?

Finding the right car radio that fits your vehicle perfectly can be a daunting task. Check out our comprehensive guide on which radio fits your car to make the selection process smoother. You will find there all you need to match the right size, features, and brand to your specific vehicle.

What Is Aux in Car Stereo? Everything You Need to Know

Almost every modern car stereo comes with an auxiliary (AUX) input, but not everyone understands its use. Learn everything you need to know about AUX in car stereo, how it enhances your audio experience, and how to connect various devices using this input.


Preamp outputs are one of the most critical features of a car stereo.

They allow you to run more speakers and subwoofers and add some flexibility for the future by allowing you to add custom amplifiers or signal processors without changing your entire setup.

A preamp output is an additional channel on your car stereo that you can use to connect an amplifier, equalizer, or sound processor.

Although you should use a direct one-to-one connection between the output and input in the amplifier, you can use a “Y” cable to split the signal.

This way, you can connect more speakers or subwoofers, but the downside is that the preamp output signal isn’t as strong.