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What are line output converters?

Answers to 8 common questions about line output converters

Before an LOC

Adding an amplifier to your vehicle's sound system is a great way to add more volume, and more depth and detail to your tunes, especially if you still have the factory stereo. But factory stereos don't have the preamp outputs needed to connect an amp. That's when a line output converter can help.

Q: What is a line output converter? 

A: A line output converter, or LOC for short, converts a speaker-level output signal into an RCA preamp-level signal. This lets you connect the radio to the amplifier. It can also be used to connect a new radio to a car's factory amp (see below).

Q: How can I connect an amplifier to my car stereo that doesn't have RCA preamp outputs?

A: Over the years, we've been asked thousands of times, "How do I install a line output converter?" It's a great question. If your stereo doesn’t have preamp outputs, or not enough of them, a line output converter is a great solution. You connect the stereo’s speaker wires to the LOC’s inputs and use RCA cables to run the signal from the LOC to your amplifier. 

How to install a line output converter

Q: Do factory radios have preamp outputs?

A: It's extremely rare for a factory radio to have preamp outputs, so an LOC provides the connections you need to add an amp. Many folks don't want to replace their factory radio, because of its look in the dash or the fact they have a leased vehicle. However, they can still upgrade the sound in their system by tapping into the speaker wires for the audio signal. A line output converter provides the connectivity needed to do it in most cases.

AudioControl LC2iB 2-channel line output converter

The AudioControl LC2iB is a popular LOC for adding an amp or powered sub to an audio system.

Q: Will I lose the sound from the speakers connected to the wires I'm tapping for the line output converter?

A: Normally you would cut the speaker wires and run them to the LOC, then run new speaker wires from your amp back to the other side of the cut wires (to send signal to your speakers).

But if you’re adding an amp to power additional speakers or a subwoofer, then you’ll just tap into the stereo’s speaker wires to pick up the audio signal needed to feed your amp. As long as you’re only tapping the wires (using wire taps or PosiTaps, for example), then you'll still get audio from those speakers, and the LOC will get the signal it needs for your amp to power the additional speakers.

Q: Why are some line output converters much more expensive than others?

A: Some converters provide more features and power handling than others. So, it's important to know the total power output of the signal going into LOC you choose. We list the maximum RMS wattage that can go into to the line output converters we sell. 

In terms of added features, some converters include higher preamp output voltages, which keeps the audio signal to your amp ultra-clean. Others can include bass restoration circuitry or equalizers on board too. It's all a matter of the power you'll be working with and how much you want to tweak your system.

Q: Are there amps that don't require a line output converter?

A: Yes, definitely. Amplifiers that offer speaker-level inputs don't require a separate line output converter to tap into existing speaker wires to get their signal. Many powered subwoofers offer this feature, too. The speaker-to-line level conversion is done inside the amplifier. Check out our selection of amplifiers with speaker-level inputs.

Speaker level inputs

This amp includes an adapter that lets you connect your speaker wires directly, without needing a line output converter. The adapter plugs into the amp's "high level input" connection.

Q: Would I ever want to use a line output converter over an amp with speaker-level inputs?

A: As mentioned above, some upgraded converters offer additional features that an amplifier you're considering doesn't have, such as on-board equalizers, higher voltages on the preamp outputs, or restoration circuitry that resets the factory system's equalizer to a flat setting. This lets you start from scratch in terms of setting up the sound the way you want it. So, it really depends on what type of system you want to create.

Q: Someone said I need a line output converter to install a new stereo. Why is that?

A: Line output converters are sometimes also needed to install a new stereo in a vehicle with a separate factory amplifier. They’re used in conjunction with vehicle-specific wiring adapters to make the new high-powered stereo work with the factory amp. They often offer gain adjustments that let you balance the output from new radio to the input sensitivity of the factory amp for the best sound. When you use our OutfitMyCar™ application to shop for a new radio, we'll let you know if an LOC is needed.

More questions?

So even if you're working with a radio with no RCA outputs, you can still add some amplification to your speakers or add a subwoofer. If you have additional questions, check with one of our knowledgeable Advisors. We're here to help.

line output converter installed
  • Hank Craft from El Dorado

    Posted on 1/7/2023

    I have 2 powered subs that I am going to install in my Jeep Gladiator using my factory head unit without the Alpine audio system upgrade. Can I do this with one line output converter and RCA cable Y splitters or do I need 2 LOCs?

  • Chris Batchelor

    Posted on 12/23/2022

    Since distortion levels at the output of an amplifier, and distortion can be high at low output levels as well as being high at high output levels, it's not clear how sound quality can be optimized with variable amp to speaker outputs converted to line level.

  • Dustin stinson from williamstown

    Posted on 11/24/2022

    so on a line output converter there are two inputs, L+ L- R+ R- since we have 4 wires, LF LR RF RR should we double up those 4 wires so its 8 Wires into the 2 inputs or does it just need 4 wires

  • Clay A Myers from Spring Creek nv 8981

    Posted on 11/22/2022

    Do I need a loc for soundstream stealth amplifier ST41200D? Also do you have a high level wiring harness for the same unit thank you

  • Andres Cabreja from Chattanooga

    Posted on 10/26/2022

    If I tap into my factory radio and place a line out converter will I loss the availability to tune sound volume (front vs back speakers) for sound staging? Or will a qualified amp allow me to adjust those settings with a pre-amp line out coverter?

  • mooseandsquirrel from Atascadero, CA

    Posted on 7/16/2022

    Seems the LOC would need to show several different loads to the stock radio. If it subs for a speaker then it would need to be 8-10 ohms, but if you tap into a speaker wire (car speaker still attached) then the input would need to be a high impedance. In both cases they would be high voltage inputs.

  • Samuel Cruden from Cottage Grove

    Posted on 5/1/2022

    I am putting in a new stereo system and I bought a sub with an amp package and the amp is one channel but then I was going to get a 4 channel amp for my speakers then I started reading about LOCs. Can I plug a LOC into 2 amps or are there like 2 channel LOC options or do I need to get a 5 channel amp and do one amp plugged into an LOC?

  • Samuel Cruden from Cottage Grove

    Posted on 5/1/2022

    I am putting in a new stereo system and I bought a sub with an amp package and the amp is one channel but then I was going to get a 4 channel amp for my speakers then I started reading about LOCs. Can I plug a LOC into 2 amps or are there like 2 channel LOC options or do I need to get a 5 channel amp and do one amp plugged into an LOC?

  • Rod from New York

    Posted on 4/25/2022

    Hooked up a powered subwoofer amp to the factory radio using the high level inputs - the sub sounds incredibly low - would using the RCA inputs help loudness?

  • Connor Crist from Lakeside

    Posted on 6/23/2021

    If I want a sub that takes 600 rms and my amp can push like 600 rms to that sub then if I get a line out converter that has 400 rms (most of these converters on this page say 400rms) then will my amp and sub only get 400 rms and be underpowered?

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