If you’re new to car audio, then you are probably wondering what all the hype is over having big subwoofers and lots of amplifiers. If you’ve ever asked yourself what does an amplifier do, you’ve come to the right place. In this post, I will explain what a car amplifier is and what it does within your sound system. I will also cover the different types of amplifiers to help you decide which one will fulfill your car audio-related needs.

The Amplifier: What Does It Do?

In simple terms, a car amplifier boosts the electrical audio signal from your head unit to power high-power speakers and subwoofers. Almost all head units are limited in the amount of power they can send to a speaker. Your head unit can power your typical door speakers and such, but adding a subwoofer to the mix will require a tremendous amount of power to get that “hit you in the chest” type of bass. In order for that subwoofer to work properly, the amplifier takes the lower-power audio signal from the head unit and boosts it to a level that can really make that subwoofer move some air.

How Do Amplifiers Work?







Car audio amplifiers utilize specialized internal power supplies and circuitry to take the electrical audio signal from the head unit, amplify it, then send that “boosted” signal to the speaker terminals. 


All car audio amplifiers utilize the same basic components to perform the task it was designed to do. These components are divided into sections on the PCB (printed circuit board). These basic sections are as follows:

  • A DC to DC power supply (sometimes called a step-up power supply). This power supply is needed to create the power it takes to power a larger loudspeaker from a 12 volt powered audio source. This power supply can take the 12-volt power source and multiply it many times over.
  • Crossover circuits. This circuitry ensures that the proper frequencies are being sent to the speakers in order to provide the best possible sound quality and to avoid damage to the speakers.
  • Bridging circuits. Bridging circuits allow the amplifier to “bridge,” or combine, speaker outputs in order to provide an increase in power output. Bridging an amplifier’s speaker terminal is taking two channels and combining them to make a single channel.
  • Noise filtering circuitry (also known as “ground loop” noise). This circuitry helps to eliminate any unwanted “noise” from the audio signal. This “noise” can be alternator whine or some other interference within the audio signal.
  • Audio signal inputs. The audio inputs can be provided via the typical RCA-type input or speaker-level inputs (high-level input). I discussed what the high-level inputs are and how to utilize a line output converter to convert these speaker inputs to RCA outputs in this post if you’d like to know more. 

The Power Supply

The most critical, or important, component of the amplifier is the power supply. This power supply is called the switch-mode power supply, or SMPS. It is the part of the amplifier that creates the higher voltage power from the 12 volts electrical supply source. The amp’s power supply is called switch-mode because it quickly turns transistors on and off, alternating the 12-volt power supply to the transformer. This switching, in turn, causes the transformer to produce high voltages on its output. The switching will also produce both positive and negative voltages. This will allow a fuller range of polarity when the signal is delivered to the output.


The input section of the amplifier is just that, the input. This is where you will connect your head unit’s output via RCA patch cables or through speaker-level inputs. But, even though it seems pretty self-explanatory, the input circuitry of the amplifier actually handles more tasks than that. The input section performs these jobs:

  • Allows the amplifier to connect to your head unit using RCA or speaker-level inputs.
  • Contains circuitry to help eliminate noise from being boosted and sent through the speakers or subwoofer.
  • Performs the crossover tasks.
  • Handles the gain adjust of the amplifier. We will discuss the gain later on in this post. 

Preventing “Ground Loop” Noise

Ground loop noise, also known as “alternator whine,” is an annoying buzzing or “whine” that can be heard through the speakers or subwoofer and can increase or decrease with engine speed. Ground loop noise is typically caused when an electrical current travels through the body panels of the vehicle and into the audio system. 

Luckily, most new amplifiers today contain the necessary circuitry components to nearly, if not completely eliminate all of this frustrating noise.


Most, if not all amplifiers will have crossover functionality. This is a great feature to have because it can help you to fine-tune the frequencies that are sent to specific speakers. Most crossovers will have high-pass and low-pass adjustments that allow you to block or allow frequencies from being played. For example, the low-pass crossover will be used to send only low-end frequencies to the subwoofer. Depending on the size (diameter) of the subwoofer, these frequencies can range from 100 Hz and below. On the other hand, the high-pass crossover would be used to control the door speakers or tweeters.

The GAIN: It’s Not A Volume Knob!








As the title of this section indicates, the gain is in NO WAY a volume knob! The amplifier’s gain adjustment is used to match the speaker, or subwoofer, output signal with the head unit, or source, input signal.


Even though amplifiers feature many other adjustments, the gain, in my opinion, is the most important adjustment of the amplifier and needs to be set properly in order to get the best possible sound quality and to prevent damage to your speakers or subwoofer. DO NOT just turn the gain like a volume knob. Just because your speakers are getting louder, doesn’t mean they are function properly. To ensure your amplifier gain has been set properly, you can use tools such as an oscilloscope (o-scope), or the SMD DD-1 Distortion Detector.

Output: The Channels

All amplifiers have audio output channels. These channels are the individual audio paths that deliver the audio signal to the speakers. There are different amplifier styles or configurations. They can range from a single channel (monoblock), up to 8 channels, or more. Most amplifiers can have their channels bridged, or combined, to create a single channel. This means that the user can take two separate channels and connect them in a specific configuration to create a single channel. This can be useful when you want a little more output wattage, or if you want to run a single speaker such as a subwoofer. 

Amplifiers: The Benefits

Amplifiers are a great addition to a car audio system. There are several benefits to installing one in your vehicle. These include, but are not limited to the following:

  • Increased audio output (GET LOUD!)
  • The ability to add a subwoofer to a boring stock audio system.
  • The ability to tweak, or tune, tune the audio signals a bit more than the stock audio system will allow. 

This is just my opinion, but I really see no reason why you shouldn’t consider adding an amplifier and speaker or subwoofer upgrade to your vehicle. 


If you were unsure of what an amplifier was and what it could do for your audio system, I hope this post has given you some insight and understanding of some of the basics of the car audio amplifier.

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** Please note that this article provides general information on amplifiers in a car audio system. Keep in mind that not all vehicles are the same and may require different installation methods and techniques to ensure a safe and effective install. By no means, am I a professional mechanic or car audio installer, and D4S and I, are not liable for any damages caused to your person or vehicle by following these instructions. Please consult a professional if you have any questions or concerns regarding your own vehicle and how to perform modifications such as the one explained in the previous statements


Amplifiers: General | Car Audio 101

About The Author Brandon L

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