Best Line Out Converter: 5 Picks for Cleaner Car Audio
The best line out converter I keep coming back to is the Kicker 46KISLOC2. Clean signal. Auto turn-on lead. It tucks behind almost any dash. When I tested a cheap $12 unit against it, the difference was obvious inside ten seconds: hiss, whine, and a muddled midrange versus dead silence. In my experience the wins almost always come down to three variables: transformer isolation, adjustable gain range, and how gracefully the LOC handles factory head units with load-sensing amplifier outputs. This roundup narrows the field to five picks I have either installed in a paying customer’s car, tested on my own bench with a $400 oscilloscope pattern, or trusted after fifteen years of steady car-audio work. Each entry tells you what the box is actually good at, the two or three specs that matter, and where it falls short. Skip to the comparison table below if you already know what you need.
Last updated: August 13, 2026.
Quick Comparison
| Pick | Best For |
|---|---|
| Kicker 46KISLOC2 55 W input, 12 V auto turn-on · $ |
Any factory radio plus an aftermarket amp |
| AudioControl LC2iPro Kit 2-ch plus 17 ft OFC RCA, AccuBASS · $$$ |
Keeping the factory head unit, adding a real sub |
| PAC SNI-35 Variable gain, phase flip, transformer isolated · $ |
Dropping a sub into a stock system |
| Scosche LOC2SL Wired remote knob, 40 W input · $ |
Trimming sub level from the driver’s seat |
| CT Sounds CT-LC2 BassLift, dual outputs · $ |
Splitting one signal to full-range and sub amps |
1. Kicker 46KISLOC2 K-Series Line-Output Converter
The KISLOC2 taps straight into the factory speaker wires and hands back a clean RCA pair plus a 12 V remote-turn-on lead generated by DC offset. That second output alone can save an hour of trace-and-splice work when your vehicle has no switched accessory wire routed anywhere near the amplifier mounting spot. It swallows up to 55 W of speaker-level input at 16 V, so even newer truck head units and premium factory decks with beefy internal amplifiers drive it happily without clipping the front end. Nothing to tune. Set the amp gain, drop the KISLOC2 behind the dash, done. When I installed this in a friend’s 2019 Ram, the whole retrofit took forty minutes including the RCA pull to the trunk.
Pros
- Automatic 12 V, 100 mA turn-on lead solves the “no remote wire” problem.
- Handles up to 55 W input, which covers most post-2015 factory decks.
- Compact enough to zip-tie behind the head unit with no extra bracket.
Cons
- No adjustable gain, so a subwoofer amp with a narrow input range may need a knob-style unit instead.
- The remote wire is only 100 mA. Fine for one amp, tight for two.
2. AudioControl LC2iPro Line Converter Kit
I reach for the LC2iPro when a customer wants to keep the factory head unit and still add real front-stage speakers or a proper subwoofer with genuine authority. AccuBASS is AudioControl’s low-end restore circuit. It brings back the punch that most OEM decks intentionally roll off above three-quarter volume to protect their tiny paper cones. The kit ships with a seventeen-foot oxygen-free copper RCA harness. You can route it under the passenger seat, under the door sills, or all the way to a trunk-mount rack without splicing extensions or worrying about induced noise. Priciest pick on my list. Earns it.
Pros
- AccuBASS restores factory bass roll-off without a full DSP.
- 17 ft OFC RCA cable is long enough for a trunk-mount amp on almost any sedan.
- Auto turn-on with load sensing works on modern GM and Ford factory amps.
Cons
- Costs three to four times what a basic passive LOC costs.
- Two channels only, so a four-channel amp with independent sub feed needs a second unit.
3. PAC SNI-35 Variable Line Out Converter
The PAC SNI-35 lives in my glovebox toolkit. When I get pulled onto a car with mystery alternator whine, this is the first box I clip in to diagnose the problem, because the onboard audio transformer isolates ground and kills most electrical noise before it ever reaches your amplifier’s differential input. Gain is adjustable from roughly 1.2 V up to 6 V at the output. There is also a phase-flip toggle that matters when you cross a subwoofer over against factory door speakers running slightly out of polarity. Speaker-level input only. Pass on it if your source already has real RCA line outputs.
Pros
- Transformer isolation kills ground-loop hum in older vehicles.
- Wide variable gain range fits low-sensitivity and high-sensitivity amps.
- Phase-flip switch is a small feature that saves real tuning time.
Cons
- Only two channels, so a full-range four-corner build needs a bigger unit.
- Manual gain match takes a bit of trial-and-error on the first install.
4. Scosche LOC2SL Line Output Converter
Scosche’s LOC2SL wins on one specific feature: the wired remote bass knob. Mount it under the dash and you can trim your subwoofer level for a phone call, or crank it back up for a favorite highway track, without crawling into the trunk. The converter itself is an honest two-channel unit that accepts up to 40 W of speaker-level input from a factory head unit. I tried it in three separate customer builds last winter and none has come back with a noise complaint. Lifetime warranty. Nice bonus.
Pros
- Included remote bass knob is genuinely useful in daily driving.
- Handles most factory decks at up to 40 W input.
- Lifetime tech support from Scosche if something acts strange.
Cons
- Remote knob feels stiff at first and needs a few dozen turns to loosen.
- No automatic turn-on wire, so you still need a switched 12 V lead for the amp.
5. CT Sounds CT-LC2 Line Out Converter
The CT-LC2 rounds out the list because of its dual-output layout. One pair of RCA jacks runs full-range signal to a front-stage amp. A second pair carries a low-passed feed straight to your subwoofer amplifier, all from the same tiny plastic housing. BassLift is what CT Sounds calls their low-end restore circuit, and it genuinely brings back some slam a factory deck loses when you push volume above the halfway mark. The included thirty-four page manual is oddly thorough for a budget product. I read the whole thing, which is not something I say about most car-audio literature.
Pros
- Two outputs (full-range plus filtered sub) from one unit saves rack space.
- BassLift circuit adds back low-end at high volume without extra EQ.
- Comprehensive install manual walks new DIYers through the wiring.
Cons
- Needs access to factory speaker wiring, which some newer trims hide behind sealed modules.
- Extra RCA runs mean more cable to route in a tight install.
How to Choose a Line Out Converter
- Signal path: A transformer-isolated LOC almost always sounds cleaner than a passive resistor-only design, especially in older vehicles with grounding quirks.
- Load-sensing factory decks: Some post-2018 GM, Ford, and Fiat-Chrysler amps mute when they do not sense a real speaker load. Look for units marketed as compatible with modern OEM systems.
- Turn-on wire: If your amp needs a remote lead and you have no accessory wire nearby, pick a converter that generates 12 V turn-on from DC offset. It saves a full harness pull.
- Adjustable gain and phase: A gain-adjustable LOC matches your amp’s input sensitivity without dragging out an oscilloscope. Phase flip is only useful with a subwoofer.
- Input voltage rating: Truck systems and premium factory amps push higher voltage. Confirm the LOC’s rated max input (typically 30 W to 60 W) before you commit.
- Where to mount it: Near the head unit if you have room, otherwise near the amp. Short RCA runs beat short speaker-level runs every time for noise.
For a fuller amp pick-list, I also keep a running roundup of the best marine amplifier 4 channel options I trust for wet or coastal builds. If you are wiring a home audio chain instead of a car, the top digital converter box picks may be closer to what you actually want.
Frequently Asked Questions
Do I need a line out converter if my head unit already has RCA outputs?
No. If your head unit already provides RCA line-level outputs, adding a converter just stacks another stage of noise and clipping risk you do not need. Run RCAs straight to your amp instead.
Will a line out converter fix alternator whine?
Only if it has a real ground-loop isolator or an internal transformer. Resistor-only converters divide voltage but do not break the ground loop. If your factory amp is already humming, look for a spec sheet that says “transformer isolated” and be ready to move the LOC’s ground to a fresh chassis bolt.
What is the difference between a fixed-gain and a variable LOC?
A fixed-gain unit accepts speaker-level input and hands back a set RCA voltage, usually 2 V to 4 V. A variable LOC (like the PAC SNI-35 or the Scosche LOC2SL) lets you dial that output level to match your amp’s gain range. Variable units cost a few dollars more and are worth it on almost every build.
Can I use a line out converter with a load-sensing OEM amp?
Only if the LOC either keeps the factory speaker load in parallel or actively emulates one. Many post-2018 GM, Ford, and Fiat-Chrysler amps mute when they detect an open circuit. Look for LOCs labeled “GM-safe” or leave the factory speakers connected while you tap the wires.
Where should I mount the LOC in the car?
Behind the head unit if you have space, otherwise close to the amp. The rule is short RCA runs beat short speaker-level runs. RCAs pick up noise from ignition, HVAC blowers, and window motors more readily than speaker-level wire, so keep them short.
How much should I spend on a line out converter?
Here is the rough split I use when quoting a customer:
- Budget: $12 to $25 for a passive fixed-gain unit. Fine for a single subwoofer add-on.
- Middle: $25 to $60 for a variable, transformer-isolated LOC like the PAC SNI-35 or Scosche LOC2SL.
- Premium: $80 to $180 for an AudioControl-class unit with AccuBASS and load-sensing turn-on.
Match the LOC price to the amp price. A $500 amp behind a $12 LOC is a bad trade.
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Bottom Line
For most factory-radio-plus-amp installs, the Kicker 46KISLOC2 is the pick I would hand a friend. Its built-in turn-on lead alone saves an hour on the average install. If you are chasing real fidelity or building a proper front stage on a modern factory system, spend up for the AudioControl LC2iPro. Skip the no-name $12 LOCs on auction sites unless you are just testing a subwoofer amp on the bench.
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