Best Head Units for Sound Quality
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The lack of RCA jacks shouldn’t stop you from hooking up your amp to your stock radio and improving your entertainment experience. You have several options. This article presents three top ways you can hook the amp up and answers to some of the most commonly asked questions on this topic.

You can hook up an amp without RCA jacks by using a line output converter, the amp’s high-level inputs or a speaker wire to RCA adapter. 

Here are three ways to hook up the amp without RCA jacks:

Method 1: Use a Line Output Converter (LOC)

A LOC converts the high-voltage, speaker-level signal to a preamp-level signal. Power amps accept this type of signal. 

The converter consists of a transformer as well as a high-voltage resistor.

Line Output Converter

Here are the exact steps you need to hook up your amp without RCA jacks:

  1. Hunt down the leads connecting the factory radio and amp to the speakers (Check behind your car’s head unit. You’ll likely find it here).
  2. Using wire strippers, strip away one inch of the wire’s insulation-from each wire.
  3. Adjust the amp’s gains to a midway setting, turn on your volume, and adjust the volume to acceptable levels.
  4. Using a screwdriver, adjust the amp’s detents and the gains until you begin to sense some distortions creeping in. Turn the gain down gently until you the distortion disappears.
  5. Turn the head unit’s volume up until the distortion from the amp disappears as well. Adjust the gain further if you still sense it.

You shouldn’t opt for this method if you are on a tight budget. Some of the line output converters are costly. You should also purchase LOC to use it.

If you have no budgetary issues, you go for it to get a pure and ultra-clean audio signal.

Method 2: Use Amp’s High-Level Inputs

If you want an alternative way to hook up your amp without RCA jacks, ensure you use the speaker-level inputs (high-level inputs).  

High-level inputs convert the voltage to a version that your amp can manage. You get a well-defined sound if you follow the right steps to connect it.

Amp High-Level Inputs

Here are the steps you can follow to wire a high-level input on your amplifier:

  1. Disconnect the battery’s negative terminal to minimize the risk of a short circuit.
  2. Run the red power wire from the amplifier kit in your car’s passenger cabin.
  3. Route the power wire to the battery and connect it to the fuse holder.
  4. Mount the holder and fix the connections to the head unit and battery.
  5. Route the red and blue wires under the door panels or seats to the amp.
  6. Strip back a small portion of the right and left speaker wires and splice in those that lead to your amplifier. Do this for each of your speakers or subs.
  7. If necessary, run your wires under the door damp or the floor carpeting.

This method is also wonderful if you prefer a cheap option. However, since some amps lack speaker level-outs, it might not serve you in some cases. High-level inputs also don’t offer the cleanest signals.

Step 3: Use Speaker Wire to RCA Adapter

Another important way to hook up your amp to a stock radio is to use speaker wire adapters. These adapters convert speaker wires into RCA plug connectors. So, if you use them, you can connect your car stereo’s speaker outputs directly into your amplifier.

Use Speaker Wire to RCA Adapter

Hook the adapter up to your vehicle’s rear speaker wire to use this method. Harness and plug it into the RCA cable input.

Some of the best adapters that you can buy and use to do this are Rockford Fosgate RF12SW and Kicker 46KISL.

This method will not serve you if your amp doesn’t accept high-level input signals on your RCA inputs. 

However, it is the best option if your amplifier does this. RCA adapters are cheap and allow for clean installation. Moreover, the signals require limited amplification. So, most supported amps work pretty well, irrespective of the workload.

FAQs

How to hook up an RCA adapter to a stock radio?

An RCA adapter offers you the best way to hook up your amp to your stock radio. The best strategy is to wire the adapter to the radio successfully.

To achieve this goal, you require two RCA plugs. Connect wires from your speaker to the RCA plug. See the picture above for more on how to do this fast and securely.

How to tap into rear speakers for subs?

Many powered subwoofers have high-level inputs. This makes it easier to tap into the rear speaker wires.

You can use speaker wire if your vehicle has a factory subwoofer. Another great solution is to use a basic line-out converter. It should tie into the loudspeaker wires and turn them into an RCA output. This applies if the amp lacks high-level inputs.

Consider using something like an audio control (LC2), a high-end powered line-out converter if you need another option.

How to hook up amp with high-level input?

Hooking up an amp with high-level inputs is one of the most effective ways to wire amplifiers to stock radios. Factory radios often lack dedicated outputs for amp “RCA” or “preamp outputs.” So, most outboard power amplifiers have high-level inputs. You can use them to tap into the speaker wires for excellent signal flow.

To hook up an amp with high-level input, you need to disconnect the battery’s negative terminal to mitigate short circuits. After that, run the red power from your amplifier kit through the car’s firewall. 

You also need to route the wire to the battery and then connect it to your fuse holder for the best result. Next, ensure you mount the fuse holder and secure your connections to your car’s head unit and battery. If you do this, you will get a lot of power. Before proceeding, route your power and turn-on wires under the door panels or seats to the amp. You’ve now tapped power.

Now strip back a small fraction of the car’s coded right and left speaker wires for each of the speakers or subwoofers you intend to use. Slice in wires that lead to the amplifier. Run your wires as you deem suitable. That’s all.

Can I Hook Up Multiple Amps With A Single RCA Jack?

If you do have an RCA jack, you can actually hook up multiple amps with it using a Y splitter cable. You can check out our article on how to hook up multiple amps with one RCA jack to learn more.

Conclusion

Now you have nothing to worry about if you want to hook up your amp to your radio but have an old head unit with no RCA jacks. You might need to do a little more to achieve your goal if the jacks are unavailable, but the effort is worth it. Choose one of the three methods we’ve shared here that suits your needs, and you’ll be able to continue with your entertainment plans without any interruption.