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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 by email, phone, or online chat. We're here to help.

line output converter installed
  • Kelly

    Posted on 11/5/2018

    Hi, I have a 2014 Mazda 3 SP25 GT with the Bose setup. I am wanting to add a Kenwood KSC-PSW8 underseat sub do I require a LOC tapped in to the front speaker wire after the Bose amp or is there a better way to add the sub?

    Alexander Hrabe from Crutchfield on 11/6/2018
    Kelly, I've passed your question along to our Advisors. Someone will contact you soon to make sure you get the right gear for your vehicle. But the quick answer is that Kenwood includes a 14' speaker input harness for connecting the sub to a factory radio. Or in your case, the factory amp. You can splice it to the speaker wires and plug it into the sub's RCA input.
  • Rich from illiopolis ill

    Posted on 9/22/2018

    I have an LOC box to hook up an amp to my factory radio.what's the best way to wire it up.power wire wise.some one said to hook up the yellow power wire to the amp.but when I do that the power light on amp goes from Green to Red.any help would be appreciated.thank you.

    Alexander Hrabe from Crutchfield on 9/24/2018
    Rich, your best bet might be to connect to the battery, but you could try out tapping into factory stereo power. Keep in mind that if you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.
  • Grant

    Posted on 9/21/2018

    From what I can understand, if you have a factory amp in your vehicle, you should always tap into the speaker wire after they've been amplified as opposed to tapping directly from the head unit. Is this correct?

    Alexander Hrabe from Crutchfield on 9/21/2018
    Grant, yes, you're correct. If you have any questions about installation and you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.
  • Thad from Sioux city

    Posted on 7/23/2018

    I want to replace rear deck subs in 04 Concorde, it has infinity premium sound system. Do I want the subwoofer signal before the factory amp or can I run the powered speaker(after amp)wires into my line converter????

    Alexander Hrabe from Crutchfield on 7/23/2018
    Thad, you want to tap into the signal after the amp, but there's a chance, with that premium factory system, that you might not be getting a full range signal. If you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.
  • Dave Delamere from Crutchfield

    Posted on 5/23/2018

    Ben, you'll need a new LOC (or receiver with 5-6 preamp outputs), since the Scosche LOC90 is 2-channel only and won't retain fading capabilities. Conceivably, you could do the RCA splitter if fading wasn't needed, but output from a mono amp would have to be full-range. But the signal quality might not be ideal. I've passed your question along to our Advisors. Someone should contact you soon to help.

  • Ben Henshaw from Charlottesville, va

    Posted on 5/21/2018

    I have a loc 90 connected to a mono sub amp powering a 12 inch subwoofer. I wanted to upgrade my 4 factory speakers and add on a 4 channel amplifier. Do I need a different LOC? Or can I just run rca cables from the output on the mono amp to the 4 channel amp with rca y splitters?

  • Alexander Hrabe from Crutchfield

    Posted on 5/14/2018

    Jason, unless I'm misreading your question, you'd hook up your speakers to the amp. If you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.

  • Alexander Hrabe from Crutchfield

    Posted on 5/14/2018

    Dave, I've passed your question along to our team of Advisors. Someone will contact you soon to help you take your system to the next level.

  • Jason from Wabasha, mn

    Posted on 5/12/2018

    I'm hooking up factory stereo to 2 channel amp, I have an LOC , no subs, do I hook anything up to amp speaker connections? Thanks

  • Dave Seibel from Moorhead

    Posted on 5/12/2018

    I have a 2014 Honda Crv ex-l with 7 channels, no navigation. includes a stock amplifier with 7 speaker outputs, with separate wiring for the front door tweeters and woofers (4), two full range rear doors (2), and one for the stock subwoofer. I also have a soundstream Picasso mono sub amp piggybacked onto the stock amp speaker input, driving a Jl microsub. Want to replace door speakers and install a new 5 channel amp, which would also replace sub amp. The stock amp has an internal crossover, but also retains some stock Bluetooth functions, so wish to maintain it, but use a processor to clean up it's eq, and sum the front channel tweeters/woofers, to use the supplied crossovers with new front door component speakers. So probably looking at 8 channel in/6 channel out processor feeding new 5 channel amp. Looking at soundstream 5 channel amp. I'm thinking Jl Fix86 might be a good processor choice. I want to remove the old stock sub (under the passenger seat) completely, mounting new processor & amp there (the current Soundstream amp is already mounted there next to stock sub). The Honda stock sub is worthless...the Jl microsub in the cargo area delivers terrific bass. So, keep stock unit, add new processor to sum front channel tweeters/woofers, keeping rear door speaker line (for fadar), and overall clean up EQ/loudness contour, feeding new 5 channel amp driving new speakers (component front, coax back, + current Jl microsub). Thoughts?

  • Buck Pomerantz from Crutchfield

    Posted on 3/31/2018

    Max, The information I can find for that amp states that it has speaker-level inputs - a built-in line output converter.

  • Max from Tel-Aviv

    Posted on 3/31/2018

    hello , i want install amp and sub into my car without replace the original UH ( i have Auris2014 ) i have amp Alphasonik PMZ6004A , should i use convertor or this amp has it inside ?

  • Alexander Hrabe from Crutchfield

    Posted on 3/13/2018

    Kasen, if you're just adding in those front speakers, you should be good, but give us a call if you have any further questions along the way.

  • Kasen Johnson from Kingwood

    Posted on 3/9/2018

    Currently I have a LC2i converter connecting my amp and sub to the factory head unit. I am now looking at upgrading my factory front door speakers and powering them with a separate amp from my sub. Do I have to upgrade my converter to something such as an LC6i or can I just buy an amp with built in converter and still run my sub amp with the same converter. Thank you.

  • Alexander Hrabe from Crutchfield

    Posted on 10/30/2017

    Jay, if you don't mind losing fade control, the 2-channel will work, but you might consider upgrading to a 4-channel. I've passed your question along to an Advisor to help you find the right solution for your system.

  • Jay G from Allentown

    Posted on 10/26/2017

    Will a 2 channel LOC do the job if I have a factory stereo, 2 door speakers, 2 rear pannel speakers , a subwoofer enclosed along with a 5 channel amp?

  • Alexander Hrabe from Crutchfield

    Posted on 7/26/2017

    Charles, I checked with Tech Support and they suggested using a Sine wave test tone of appropriate frequency and measure the loaded output of the LOC with an AC meter. Hope that helps! Keep in mind that if you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.

  • Charles J Robinson from Buda

    Posted on 7/22/2017

    So... no response on testing the outputs for voltage consistancy between channels on a LOC?

  • Alexander Hrabe from Crutchfield

    Posted on 6/19/2017

    Eduardo, great question. If you bought your LC8i or your amplifier from Crutchfield, then our Tech Support team will be able to help you figure the best way to get to install that AudioControl piece. Have your invoice on hand when you call because they'll need some information from that. If you bought your gear somewhere else, you can still get ur world-class supporto for only $30.

  • Edwardo from Brownsville, texas

    Posted on 6/18/2017

    I want to install an lc8i on my 2016 f150 which comes with a sony factory system. However, i am told i need to use the "summing" jumpers because the factory amp has a built in crossover. So what is the best way to wire the lc8i?

  • Charles J Robinson from Buda

    Posted on 6/16/2017

    One more question. How do I test the preamp outputs from a LOC to make sure voltage levels are good, and equal on both channels?


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