How To Hook Up an Amplifier Without RCA Cables

How To Hook Up an Amplifier Without RCA Cables

Having to hook up an amp without RCA jacks is more common than one thinks. When it comes to wiring up an aftermarket amplifier to a car stereo system installation, there are a number of roads that can be taken in regard to approach.

It’s all dependent on the gear being installed, the types of connectors available with the equipment, and the overall goals of the system itself.

Of course a good set of car speakers is critical, and once you’ve matched them up with a good quality car amplifier, installing them can be straight forward, but not always.

Most middle to high level styles of car audio system installs utilize an amp’s RCA ports for what is arguably the cleanest-sounding connection. This comes from the system’s head unit (radio/receiver) to the amp itself, but there are times which demand a different solution, like when head unit has no RCA outputs on the back.

It’s more common than you think, and if you’re reading this you’re probably in this predicament right now. So, let’s look into how to hook up an amp without RCA jacks.

Ultimately, there are three ways to deal with this install dilemma:

  1. Speaker wire to RCA adapter
  2. High-level inputs on an amp
  3. Line output converters.

Each come has its own set of advantages and challenges, like everything else, but worry not – the following information is going to clear up any misconceptions about all three approaches.

#1 Speaker Wire To RCA Adapter

To begin with, it can’t be stressed enough just how important an outboard power amplifier is in a mobile audio system. For those who have never experienced car stereo beyond the limits of their vehicle’s factory setup, the difference is staggering.

JL RCA to Speaker Wire Adaptor

From the jaw-dropping dynamic range offered by an amp’s high-current power to the raw muscle that drives thumping subwoofers in the trunk, amplifiers provide the visceral horsepower required to make music truly come to life.

This is to say nothing about the way a good amp will overcome that annoying road noise in many makes of cars and trucks, which can be especially irritating if the windows of the vehicle are down and the car or truck is at highway speeds.

But what many novices in the car audio world fail to realize is that a vehicle’s factory radio can in fact be used with an outboard amp – it just takes a bit of creativity and knowledge of the necessary accessories to hook it all up.

A good quality car amplifier can help you get the most from your factory system, especially when it comes to bigger vehicles like vans or full-size SUVs, where it can be especially challenging to achieve a clean, powerful sound.

This is where I get into our first solution – adapter cable from speaker wires to RCA plug.

If your amp can accept a high level input on the RCA’s (see specifications your amplifier) you can hook the above adapter up to your car’s rear speaker wire harness and then plug into your amp’s RCA cable input, which is probably the easiest way to do it.

Best adapters you can buy:

#2 High-Level (Speaker-Level) Inputs On Amplifiers

The second option to hook up an amplifier without RCA jacks is using high-level inputs, which is sometimes referred to as speaker-level inputs.

What Is A High-Level Input On A Car Amp?

High-Level Inputs allow you to hook up an amp without RCA jacks

Because factory radios don’t have dedicated outputs for amplifiers “RCA” or “preamp outputs”, most outboard power amps come with high-level inputs, which enable you to tap into the factory speaker wires for signal flow. These are referred to as high-level inputs because the voltage level is significantly higher than that of a standard preamp output connection.

Regardless, these inputs convert the high-voltage to a version the amplifier can handle. Once connected, the result is clean, well-defined sound, with high-level inputs coming standard on a variety of 2 and 4-channel amps, as well as monoblock amplifiers, which are mostly used for subwoofers.

How To Wire A High-Level Input On An Amp

The installation of an amplifier using high-level inputs isn’t much different from the procedure used when wiring one with preamp outputs. Before anything is even attempted, it is always advised that you disconnect the negative terminal from your battery to protect against a possible short circuit.

Working from your vehicle’s passenger cabin, you will run the red power wire from your amp kit through your vehicle’s firewall, route it to the battery and connect it to the fuse holder. Mount the fuse holder and secure the connections to the head unit and battery. This procedure will yield your power. At this point, you’ll also route your red (power) and blue (turn-on) wires under door panels, or seats to your amplifier.

Now that your power is tapped, it’s time to get into receiving an actual audio signal. For each speaker (or subwoofer) that you plan to drive with your amp, strip back a small part of your vehicle’s color-coded left and right speaker wires, then splice in the wires that lead to your amp (crimp or solder, and secure the connection for optimum performance).

If you intend to install your amp in the trunk of your car, it’s a relatively short path to the rear deck speakers or a subwoofer, so reaching the amp shouldn’t be a problem.

Driving front seat speakers will require you to run wiring under a door jamb or the floor carpeting to reach the speakers, however. Similarly, if your amp is mounted under the front seat, the front speakers will be easier to reach than the rear ones.

#3 Line Output Converters (LOC)

The third option to hook up an amp without RCA jacks comes in the form of a line output converter. This is a device used by many installers who have customers that don’t want to get rid of any aspect of their factory stereo – they simply want to add amplifiers and subwoofers.

What Is A Line Output Converter?

Audiocontrol LC2i line output converter

This RCA adapter for stock radio that converts the high-voltage, speaker-level signal to a preamp-level signal that’s acceptable to a power amp. A “LOC” as they are known, consists of a transformer and a high-voltage resistor, and connects to your amp using a standard RCA patch cable. The transformer of this device should be grounded, with most line output converters coming with a wire for that exact purpose.

LOCs also usually come with an adjustable gain feature, so the output feeding an amp can be tweaked to a certain extent (this is good for ensuring subwoofers aren’t overdriven when balancing an amp’s output trim levels).

What Does An LOC Do?

As we touched on in the above section, a LOC converts the high-voltage, speaker-level signal to a preamp signal that a power amp can use. This is especially helpful when installing a two channel or monoblock amplifier to an existing factory radio (or even some aftermarket systems).

Most LOCs feature up to four volts output and signal-sensing turn on with the ability to drive a relay. Some also include convenient remote-mountable volume controls for precise adjustment over subwoofer amplifier level from the driver’s seat.

Some best LOC you can buy:

How To Hook Up A Line Out Converter (LOC)

Here’s an in-depth step-by-step guide for installing a Line Output Converter…

The first thing you’ll need to do is hunt down the leads connecting your vehicle’s factory installed radio and amplifier to the speakers.  From my experience, these wires are located just behind the head unit.

From there, you will use wire strippers to strip away one-inch of the wires’ insulation – from each wire – so that the right channel of the LOC can be attached to the right speaker and the left channel of the LOC can be attached to the left speaker.

Now, the next step is to solder the converter’s wires to the speaker wires and then seal that connection with either electrical tape or a heat shrink method. The LOC must then be secured to your vehicle at some attachment point before inserting RCA cables into it and running those to your amp.

The final steps involve balancing some levels so that everything sounds as clean as possible.  This begins with adjusting your amplifier’s gains to a midway setting and then turning on your radio so that you can adjust the volume to what you feel is a comfortable listening level.

Then, slip the working end of a small screwdriver into the adjustment detents of the amp and adjust those gains until you sense distortion is creeping in, then turn the gains down until it disappears.

Finally, go back to your head unit and turn the volume up to ensure no distortion is being emitted by the amplifier.  If you hear distortion, adjust the gains on the converter and amp in response.

How To Hook Up An Amp Without RCA Jacks

Hooking up an amplifier without RCA jacks is common. Sure, most systems come with RCA jacks, and this makes life easier, but if you find yourself in the predicament, don’t be put off.

Whether you choose to connect your speakers wire with an RCA adapter, or through high-level inputs on your amp, or through LOCs, it just take a bit research and getting the right parts. Once complete, you’ll be glad you did it because the difference a good quality amplifier makes to your sound system is unreal.

61 thoughts on “How To Hook Up an Amplifier Without RCA Cables”

  1. What would you do if you want to keep the stock Bose system which has a factory amp already yet want to and an aftermarket amp to power subs?

    • Your best bet would be to get on your model owner forums and see what others have done. And remember, the signal coming out of the factory amp is already highly processed.

  2. I am trying to avoid spending more money on a stereo system. I already own a 2ch amp, a 4ch amp (both with high level input options). I want to connect the 4ch amp for components and a 2ch amp for a single sub, to my factory radio. Both amps have high-level inputs on them. Any issue with using those for the signals? What are the cons of doing this, if it is even possible?

  3. I had a sub and amp installed in my 06 Lexus is250, and there is no sound at all coming from any speakers in my car. The shop used the high level input on my RF amp rather than the LOC i provided. Would this possibly cause the problem? They think my factory amp somehow died during install, but ive never had problems with it before.

    • It must be fine without a line output converter. Two roads to the same place. You need to visit your installer to check everything.

  4. What if just want to run all new wires from the factory radio to the LOC and then to the amp to speakers without using the factory wires can I do that?

  5. Hi, can you power the front speakers of the car just with rca cables from the aftermarket deck to the aftermarket amp? Or do you have to run speaker wires from the door to the amp as well? Thanks

  6. If i hook up the LOC to my rear speaker wires to run a mono amp and 1 svc 4 ohm sub, can i attach all 4 front & rear speakers to the front speaker wires? Or do i just lose my rear speakers altogether?
    They are crappy factory 4ohm 15w speakers, and the factory head unit with no rcas

    • I wouldn’t hook up front and rear speaker wires to the same input. You will lose fade function and it could cause issues with underpowering those speakers.

  7. Hello,
    Sorry if you have already answered this question.

    I have a harmon Kardon system in my BMW, with two factory sub’s under the front seats.

    I’d like to add an additional sub in the boot/trunk and KEEP the factory subs running.
    I am considering a pioneer class D MONO AMP GM-D8701 to run a JL AUDIO 10W6V2 subwoofer.

    The amp accepts high and low level inputs .

    1. Should/can I splice the signal from the current sub’s at a high level to feed the amp. (Will the effect the current sub’s)
    2. Should I use a LOC

    Is there any benefit to using a LOC or disadvantage to using a high level inputs?

    I look forward to you thoughts on this.


    • Hi Ketan!

      The Harman Kardon sub outputs have high voltages with the 30v peaks.
      1. If you do not want to cut any OEM wires better solution is to use plug-n-play harness with LOC. The harness can be purchased from here.
      2. Or you should use the LC2i Active LOC.

  8. Thank you so much for your help you’re a real gent. It’s not often you get free advice.
    One further question, will a passive LOC be enough or do I need an active one?

    Thanks again


  9. The original amp in my 2007 Cadillac CTS (located in the trunk) took a crap. Can I just splice the old wires to a new wiring harness that fits a new amp, without having to mess around with the radio, and/or speaker wires?

    Thank you in advance!

    • You can’t remove the factory amp cause the Bose amplifier is controlling the volume, etc. You do not need a LOC after the Bose amp if the amp you pick has a high-level input. If you have the 10 speaker system it has the connector with Low Level sub wires you can use without a converter.

  10. Hello! I have a Kenwood 500 watt amplifier with speaker level and signal sensing turn on. Do I need to purchase the PAC loc 7 line output to use it if it’s already built in my amp. Please help me.

    • If your amp with built-in hi level converter you don’t need a LOC. But it depends on the make/model of the vehicle and system you want.

  11. I have a 2019 Camaro LS with the cheapest factory radio known to man. The problem is that it is a split system, the head unit is behind the glove compartment and the 7″ screen is in the dash. There is no amplifier or sub in the system as built, and the speakers are pretty bad too.

    I’m considering changing out the speakers, but not sure if that would provide much value with the low end head unit. There is no way to replace the head unit with a better one, so I am trying to figure out how to add an amp and (hopefully) make the unit sound better.

    I’m looking for the most cost effective solution, as I don’t have a lot of money to put into this. What would you suggest?

    Thank you!

  12. Hi,

    So after much research for my ’17 Mazda 6, I found that I can get a PAC to connect to the head unit that then converts it to low level RCA outputs. My plan is to connect these RCAs to a Helix DSP that has low level RCA inputs then from the DSP connect to one 4 channel amp and 1 monoblock. I want a 2 way active setup, so two tweeters, two midrange speakers and I’ll add a sub.

    So I’ll connect the front left and right RCA connections to the DSP for the front two speakers. But what about the tweeters since they’ll use their own channels, do I connect the rear left right RCA connections to tweeters even though they technically aren’t rear speakers? In other words from my front head unit, the rear speaker controls will basically be controlling the tweeters?

    Also will my sub just be controlled by the DSP and not the HU since the HU only outputs FL FR RL RR?

    • Hi Mike!

      No, the DSP will separate the signal based on the output signal you set, then 2 channels to mids and 2 channels to tweets. You only need one set of full-range stereo inputs into the DSP and you will then assign the inputs to outputs.

      Many of the Helix DSP have a high level in. So the LOC will not be needed.

  13. I would like to add my 600w amplifier to my 2016 Taurus Limited Sony sound system. Does someone make a harness that would make the installation easier?

  14. Hi. I have an old car which does not have RCA outputs in its Radio. I have also another much newer car radio which has RCA outputs in it, but I don’t want to replace my old Cassette radio because my car is old too. What are the pros and cons if I will took the easy way and put RCA adapters to the speaker wires and then put RCA to the amplifier? I have 500w amplifier and 10 inch subwoofer which is set to 8 ohms.

  15. I’m adding a RF R500X1D to a 2010 Honda Accord EX with factory amp. Is it safe to take the signal from the wires going to the factory sub, after the amp, and using them for the high level input to the amp?

  16. I recently wired a system in a 2019 Ford Mustang Ecoboost using a LOC and noticed a loud rumble when the car cuts off. I’ve checked my ground and rewired the whole thing. I’m running 2 4 ohm 12s at 2 ohm impedance and it only does it once the power to the amp and car is off.

    • Amp is staying powered up after the audio signal turns off. Try to change a remote wire’s power source.

  17. I have a 2020 Jeep Grand Cherokee and I’d like to install a 4 channel and 2 channel with the stock head unit. I’ll be running 1/0 with a big 3 upgrade but I’ve never done this with a stock radio. Any suggestions or ideas?

  18. Hello,
    is it true that all sub inputs are high signal so LOCs and converters are not needed? All you should do is just feed that into the aftermarket amp and that is it? I own 2019 Honda Odyssey with amp and 8 inch sub, want to get rid of that 8 inch sub since it does pretty much nothing and replace it with 12 inch sub, this van is so new that not much information available online.
    Thank you, every advice is appreciated

    • Hi Esen,
      The high level is the speaker level. If your aftermarket amp has a high level input – do it this way. Converter would be a good option to eliminate the factory bass roll-off.

      • Hi, I really need some advice. I just connected up some 12 inch subs with a monoblock amp to my car. It a BMW e60 with hifi system, which means 1 sub under each front seat and an amp in the trunk. I cut the wires going from the amp to the subs and connected it to a LOC. I did this instead of the rear speaker so that I would get unfiltered sound.
        I adjusted the LOC gain so that I got 2v output on the RCA with the system at 3/4 volume. I seem to not get the lowest tones when playing music. It feels like there is a subsonic filter or high pass filter on the output. Kt cuts of around 60 hz so it sounds really strange.

        I have tried the amp and sub setup with rcas from my buddies aftermarket player, and it worked like it should.
        I took plus and minus from each subs and connected it to the LOC. So that 1 rca is signal from 1 factory sub.
        I have a high level input on my amp, but couldn’t see why the LOC would be the problem. There must be something with the factory sound adjustment coming from the factory head unit and amp. Do u have any idea what it could be?

        • Hi Simon,
          The signal from your HU is a balanced differential. If your amplifier has the ability to accept a balanced signal try to use preamp signal. The signals are filtered by the amp.

  19. I want to hook up a 3rd set of speakers with a 2nd amp. My head unit only has 4-channel preamp outputs. Those outputs are hooked up to the other 2 set of speakers and the first amp. Is it as simple as just purchasing 4 sets of RCA splitter cables (1 male to 2 females) and split all 4 channel outputs? First set of outputs split to channel 1 and 2 and all 4 to Amp 1. 2nd set of outputs split to channel 3 and 4 and all 4 to amp 2. Then I will bridge amp 2?

    • Hi Kevin,

      Yes, you can use y-splitters. Does your amp have an RCA output? Then just Daisy chain them. No need to bridge amps.

  20. I have a powered subwoofer that has a soft auto turn on, so you don’t have to run a remote wire. Will that work with both, high-level and low level installs?

  21. I hooked my sub up to the wires that feed the factory sub bc it was trash. It sounds good I just don’t want to mess anything up. You think it’s ok?

  22. I’m installing an amp in my jeep commander. The amp has high level input. The plug that came with the amp has pos and neg for right and left and has ground in the middle. What do I hook that ground to?

  23. How do you install a LOC when the factory radio is already connected to 4 speakers? I want the current set up but want to install a subwoofer with an amp.

  24. Can i add 2 tweeters to my front , 2 small subs to the rear by tapping into respective channels and sending signal to amp via speaker level inputs? Keeping use of the 4 door speakers off head unit ( pioneer 210avhex , has internal amp) and driving the 2 tweeters , 2 subs of a 4 channel amp?

  25. I have a 1999 Ford Expedition that came with premium audio system (had a dub and amp in the back truck area, no longer there)…. I upgraded the door speakers and added a powered subwoofer. Looking to add a 4 channel amp for the door speaker but the RCAs from my aftermarket head unit are already going to the powered sub. How do I go about installing the 4 channel amp? Any extra gadgets that I need? RCA splitters? Fuses? Multiple channel LOC? I really don’t know where to start…. Help please???? Anyone!!!! Thanks in advance……

    • Lol I meant to say it had a SUB and amp in the back of truck….. haha sorry… stupid autocorrect….oh and I forgot to say that I’ll be adding a pair of tweeters in the near future also. So yea how do I go about wiring the 4 channel amp and tweeters? Would i need a 5 or 6 channel amp if I want to add the tweeters?

  26. Hello, Im praying you can help me. I have a 2007 chrysler sebring limited with premium audio system. Ive already had somebody that ended up hacking up my wires to factory head unit so i crimped them back together with connectors but now head unit wont power on at all so i tried to research and inquire about how to hook up the aftermarket amp and sub with the boston audio and my gig RER factory head unit and was told cant replace factory head unit and now issues with that and was also told that certain signals go through the CAN-BUS. I have now wasted money i couldnt afford and still have no music in my car. Can you PLEASE HELP me? Thank You

    • It seems like you might have a wiring problem if your head unit isn’t working. Check your wires or even your fuse?
      Have you tried getting a Line Output Converter (LOC)? This might be the problem you’re not getting a signal?
      I’m not fully clued up on myGIG receivers, tbh, but have you updated yours? It could be that…?


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