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A line output converter (LOC) is the small box that lets you add an amplifier and subwoofer to a factory stereo. It takes the speaker-level signal from your radio or factory amp and turns it into the RCA signal an aftermarket amp expects, so you keep the dash, steering-wheel controls and everything else. The right one depends on what your car already has, and choosing wrong is the usual cause of hiss, a sub that won’t switch on, or bass that disappears when you turn the volume up.
The short version
- Most cars: the AudioControl LC2i is the safe all-rounder, with bass restoration and a dash level knob.
- Newer cars with factory amps: pick a converter with selectable input load, like the AudioControl LC1i, so the factory system doesn’t mute.
- Bass fades as you turn it up: the AudioControl EPICENTER Micro restores it.
- Tight budget, basic radio: the Kicker KISLOC2 switches your amp on without running a remote wire.
Our picks
AudioControl LC2i (with ACR-1 dash remote)
The safe choice for most factory stereos.
- 2-channel speaker-level input
- Up to 400 W per channel input
- 9.5 Vrms output
- AccuBASS bass restoration
- Signal-sense turn-on
AudioControl’s AccuBASS circuit counters the bass roll-off many factory radios apply as the volume rises, and the included ACR-1 knob sets sub level from the driver’s seat. It has fixed and variable outputs and a 12 V remote output to switch your amp on.
- Handles strong factory-amp signals (up to 400 W per channel)
- AccuBASS keeps bass level as volume rises
- Dash remote included
- Remote-out triggers your amp
- No selectable input load; some late-model factory amps need one
- AudioControl says it won’t keep fader control with multiple amps
AudioControl LC1i
For late-model cars whose factory amps check for a speaker before they’ll play.
- Selectable 20 Ω / 60 Ω / 20 kΩ input load
- Built-in line driver, up to 9.5 Vrms
- Speaker- and line-level inputs
- Signal-sense, audio-sense or 12 V turn-on
Many newer factory amplifiers shut a channel off if they don’t see a speaker-like load. The LC1i’s load switch fixes that, and its line driver gives your amp a strong, clean signal. AudioControl lists no bass-restoration feature on this model.
- Load selection for modern factory amps
- Three turn-on modes
- Strong output for a clean signal
- No bass restoration
- Overkill for a basic radio
AudioControl EPICENTER Micro
For factory systems that sound thin, or bass that fades as you turn it up.
- Digital bass restoration + ParaBASS
- Selectable 20 Ω / 60 Ω / 20 kΩ input load
- 9.5 Vrms output
- ACR-4 dual-knob remote included
The EPICENTER Micro is a line output converter and bass processor in one. It restores low bass that factory processing removes and lets you set the restoration and sub level separately from the dash.
- Restores bass that factory EQ strips out
- Load selection for modern cars
- Two-knob dash remote included
- More to set up than a basic LOC
- Restoration can sound overdone if turned up too far
AudioControl LC7i
For replacing every speaker and amp while keeping the factory radio.
- 6 channels in and out
- Up to 400 W per channel input
- 8.5 Vrms output
- AccuBASS + channel summing
If your car splits the music into separate tweeter, midrange and sub channels, the LC7i can sum them back into full-range signals for aftermarket amps. It’s the step up when you’re adding more than a sub.
- Six channels for a complete system
- Summing fixes factory crossovers
- AccuBASS included
- Unnecessary for a sub-only install
- Larger and more complex
Kicker KISLOC2
For basic factory radios and a simple, one-amp sub install.
- 2-channel speaker-level input
- Up to 55 W (16 V) input
- Up to 8 V output
- DC-offset remote turn-on (100 mA)
The KISLOC2 creates a 12 V remote signal from the speaker wires, so you don’t need to find a switched power source to turn your amp on. Kicker says it presents a 60-ohm load to “smart” radios.
- Generates its own amp turn-on signal
- Simple, compact install
- From a major car-audio brand
- 55 W input limit; not for powerful factory amps
- No level control or bass restoration listed
Skar Audio SKAR2CH-LOC
For the simplest sub install on a basic radio.
- Up to 55 W (16 V) input
- 60-ohm load per channel
- Up to 8 Vrms output
- 20 Hz–20 kHz (Skar spec)
Skar’s converter covers the basics: it accepts a radio’s speaker signal, presents a load that keeps “smart” radios happy and outputs a strong RCA signal. Skar doesn’t list an automatic turn-on, so plan to run a remote wire.
- Sold by Skar Audio itself
- Strong output for its size
- Load for smart radios
- No turn-on output listed
- No level knob or bass restoration
Which type do you need?
| Your car | What to look for | Our pick |
|---|---|---|
| Basic factory radio, no factory amp | Up to ~55 W input; auto turn-on is handy | Kicker KISLOC2 or Skar SKAR2CH-LOC |
| Factory amp, most cars | High input rating, level control | AudioControl LC2i |
| Late-model car whose amp mutes without a speaker load | Selectable input load (20/60 Ω) | AudioControl LC1i or EPICENTER Micro |
| Bass fades as volume rises | Bass restoration (AccuBASS, EPICENTER) | AudioControl LC2i or EPICENTER Micro |
| Replacing all speakers and amps | Multi-channel with summing | AudioControl LC7i |
Premium factory systems from Bose, JBL or Harman Kardon often use heavy processing and separate sub channels. They usually work best with a converter that sums channels or a dedicated DSP, so tap the signal from the factory sub output where possible.
How to install a line output converter
- Find the right wires. For a sub-only install, tap the rear speaker wires (or the factory sub wires, if your car has one). Confirm with a wiring diagram for your car.
- Splice in, don’t cut through. Use T-taps or solder so the factory speakers keep playing.
- Ground it well. Use the same ground point as your amp to avoid alternator whine.
- Set the turn-on. Use the converter’s remote out, or run a remote wire from a switched 12 V source.
- Set the levels. With the radio at about three-quarters volume, raise the LOC level until just before distortion, then set the amp gain. Our clipping guide explains why this matters.
Safety first: disconnect the battery’s negative terminal before you start, fuse the power wire within 18 inches of the battery, and use a professional installer if you’re not comfortable working on your car’s electrics.
Need the rest of the install? Our guide to adding a subwoofer to a factory stereo covers the whole job, and the amp wire gauge calculator sizes your power wire. If you’d rather skip the amp entirely, a powered sub with built-in speaker-level inputs, like the JBL BassPro SL2, needs no converter at all.
FAQs
Do I need a line output converter for an aftermarket radio?
Usually not. Most aftermarket radios have RCA preamp outputs. You only need a converter when your radio has speaker outputs only, which is typical of factory stereos.
Can my amp take speaker wires directly?
Many amps, including the Kicker CXA series, have high-level inputs. They work, but a good converter usually gives cleaner sound, a remote turn-on and bass restoration.
Why does my sub cut out or hiss after adding an LOC?
Hiss usually means the converter level is too high or the ground is poor. Cutting out in newer cars often means the factory amp wants a speaker load: use a converter with 20 or 60 Ω load selection.
Where should I tap the signal?
Rear speakers or the factory sub output are best for a sub-only install. Front speakers in some cars are high-passed and carry little bass.