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What are Class D Audio Amplifiers?

James Benchman
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by James Benchman

Modern automotive audio systems are becoming more complex. What began with simple analog systems has turned into a fully developed industry with so many options to choose from.

With that said, every modern audio system have one thing in common, and that is a power amp. Car amps become a necessity as soon as you step into the custom side of car audio.

There are numerous types of amps available but Class D amplifiers are usually the go-to option. Today we are going to talk about what makes these amps the preferred choice of many audio enthusiasts and what different types of Class D amps are available today.

What Is A Class D Amplifier?

As you probably know, amplifiers are divided into different classes.

Everything began with a simple Class-A amplifier, which was analog in nature and capable of providing excellent sound fidelity to its users. However, there was just a slight issue – it was inefficient.

In the world of amplifiers, efficiency dictates how much power is being used and how much of it is being converted into heat. Class A amps are rather notorious for wasting a large amount of power by converting it into heat. Not only are you being robbed of potential performance, but you also have to find a way to deal with high temperatures which can cause issues with the electronics.

It’s a similar story with all the classes until we reach Class D.

What makes Class D amps  different is the fact that they are very efficient. Depending on which one you have, you might see zero power being wasted. They achieve this by utilizing a completely different principle of operation.

Class A and similar amplifiers push their transistors to constantly be under load. Sometimes they are working at maximum capacity, but sometimes they are working at half of that. When not fully utilized, transistors waste energy, thus converting it to heat.

Class D Amp solved that issue by using a different type of transistor that is constantly being switched on and off. While in on position, the transistor is fully conducting, and thus not wasting any energy. Naturally, when it is in off position there is also no waste of energy.

By switching the current on and off at a fast frequency, Class D amp is able to achieve maximum efficiency and zero wasted power. However, this type amplification has its own problems as well.

For starters, having a pulsed output (which is the byproduct of switching the transistors on and off constantly) produces signal distortion in the higher end of the frequency range.

There are some features that can fix this issue, but it is still the biggest problem with Class D amps. On top of that, there are more problems, but they are not as important from a user’s point of view, so we will skip them for now. With that said, the trade-off is completely worth it.

With Class D amps, not only is the efficiency maximized, but you can also create much smaller and lighter amps.

This leads us to another question, what kind of Class D amps are there? For the most part, we can recognize two specific types of Class D amps.

They are:

  • Class d monoblock amp
  • Multi-channel amplifiers

Class D Monoblock Amp

A monoblock amplifier is just a different way of naming an amp that has only one channel.

In the case of Class D amps, monoblocks are very popular due to their high efficiency. The main application for a single channel amp is to drive a powerful subwoofer. By having high wattage being pushed through a single channel, you can drive a pretty powerful sub with high levels of efficiency.

On top of that, class d monoblock amps generally work better in the lower frequency range, making them a natural choice for this type of use. Aside from their high efficiency, there are several more reasons why Class D amps are preferred in their monoblock configuration.

Size is often a big factor when you are designing an audio system in your car. Being able to push your subs with a set of dedicated amps is great, especially if those amps are compact. This way you get all the power you need while retaining a low profile.

Aside from being used for driving subwoofers, Class D monoblock amplifier is great for powering full range speakers as well.

Multi-Channel Class D Amplifiers

Unlike monoblocks, multi-channel Class-D amplifiers come with several channels available. Some have two, others have four channels, some have six. It all depends on which model you go for and how many channels you actually need.

The usual configuration of a multi-channel Class-D amp will allow for one subwoofer channel that will have more power dedicated to it and several driver channels for your standard transducers.

Most Class D multi-channel amps will allow you to bridge two or more channels. Bridging channels simply means that you are combining selected channels to drive a single speaker. A good majority of bridgeable amps will support lower impedance in order to compensate for channel bridging.

See our guide to the best 4 channel amp and  best 5 channel amp

Best Class D Amplifier Brands

Just like it is the case with other products you have bought, or are planning on buying, there are certain brands that are trusted more than others. We are going to give you a list of brands we have no problem recommending. These companies will give you the type of amplifier that will bring great performance to your audio setup.


Alpine is a brand that has been present in the audio business for quite a while now. Over time, they have established a very good reputation with users who demand absolute reliability and quality. Alpine offers a great line of amplifiers which brings some of the more advanced technologies and features you don’t get to see that often.

With that said, Alpine amps are going to cost you a pretty penny, but their quality comes at a price.


For the most part, Hifonics offers some of the best bang for the buck amps you can get at the moment. Most of their models are pretty affordable and come with a great core performance.

You won’t generally see lots of bells and whistles on a Hifonics amp, but you can bet it will push the necessary power where it is needed the most. If you are on a tight budget, this brand is a pretty good choice.

JL Audio

class d jl audio 1000 watt subwoofer amplifier

In some ways, JL Audio brings a great balance of power, quality, and price. Calling their amps entry-level or affordable would be a stretch, even though they have some models that can be described that way.

In reality, JL Audio amps are a good middle of the road solution for users who need a more refined experience, but can’t afford to spend large sums of money on an amp.


kenwood class AB car amplifier

Kenwood is another old school brand that has been with the audio enthusiasts around the world through the thick and thin. Their amps are pretty high-quality products that will deliver reliable power where you need it.

The prices are relatively reasonable, but you will struggle to find a Kenwood amplifier that is in the super affordable range.


kicker zxs class d monoblock subwoofer amp

Kicker amps are definitely among the most popular, yet most underrated models on the market at the moment. Your average Kicker unit will be built like a tank, and deliver a great, constant performance.

A lot of car audio engineers are projecting that Kicker will soon join the elite level along with the rest of exclusive brands, while some say they are already there. At the end of the day, Kicker is always going to be a good choice.

Rockford Fosgate

Quality in all price ranges. That is probably one way to describe Rockford Fosgate. This brand offers the best affordable amps that offer the type of sound quality and performance you would expect to find in a more expensive segment of the market.

Your average Rockford Fosgate amp will bring the optimal combination of performance and features. They are definitely one brand we can recommend.

NVX Audio

NVX Audio is a young brand, at least compared to most other we have mentioned so far. Their amps are still establishing a reputation, but so far the things are looking pretty good.

In almost all of the cases, the specs match the actual performance of their amps. On top of that, they seem to be pretty reliable. In terms of price, you won’t have to spend a fortune even for a bit more powerful unit.


orion class d monoblock amp

Orion’s older amps are considered to be legendary. With that said, Orion’s new line of products is looking stellar as well. We are talking about their HCCA line of amplifiers.

Lots of power, somewhat old school design, but definitely reliable performance is what you can expect these days from Orion. Incidentally, they are one of the best choices if you are looking for a bang for the buck monoblock amp.

What To Look For In a Class D Amplifier?

Now that we understand what a Class D amplifier is and what different types of these amps might run into, let’s see what are some of the most important things to look for in a Class D amplifier.

Which Type Best Fits Your Requirements?

Before you go shopping for a Class D amp, you need to figure out what type of amp you need in the first place. Are going to power a full set of speakers with it? Or do you need it for your subs only?

‘Some people are fine with having their deck driving their tweeters and full range speakers, but need an efficient amp to support that subwoofer in the back. Either way, determine what kind of application you have in mind for the amp before you go shopping for one.

What Kind of Power Do You Need?

When it comes to power, you can’t really go wrong with having more of it, but you can definitely go wrong by not having enough. There are two types of power ratings you will usually see being marketed by amp manufacturers – Peak power and RMS power.

Peak power represents that amps highest possible output that isn’t sustainable for any practical length of time. RMS power is the only relevant power rating you should be looking at when you go shopping for an amp.

With that said, when you are calculating your power needs, always leave some headroom in there just in case. It’s good to have at least 100 Watts of cushion output between your speaker system’s combined requirement and your amp’s RMS output.

Naturally, more is better. Aside from reducing the risk of you pushing the amp to beyond its limits, having more power than you need at the moment leaves room for later expansion should you need it.

Now You Know!

Class D amplifiers have completely revolutionized the world of automotive audio. No longer will you be limited by clunky Class A or A/B units that would overheat if pushed hard. Now, you can build a very competitive system that pushes tons of power without melting your trunk.

Naturally, you need to take into account some potential issues as well, but the overall performance of your average Class D unit is just better than anything else that is available.

We hope our short intro to Class D amplification has helped you to better understand this type of amps and introduced you to some of the brands you might want to check out.

On that note, we encourage you to do further research on this subject, especially if you are new to car amp systems. Just don’t be surprised if you get hooked on automotive audio for good.

About James Benchman
James Benchman
James is an Automotive Mechanic with over 20 years experience and 300+ car repairs. He is an expert with cars and has worked with different models from the biggest brands. James is a Mechanic , Husband , Father of 3 , and head of content at Caraudiologic. Learn more about us
  1. That’s a good point that before you shop for amplifiers, you need to figure out what you need it for. Like you said, you may need it for a full speaker system or just for subs, and you should know that before you start seriously looking. I think my brother is looking for a few amplifiers for his subs, and now that he has that figured out, he’s probably going to start checking out some of the supply stores in our area to find what he’s looking for.

  2. Great article…I choose to run amps for my highs and separate amps for my subs.This allows me to have much more control over what I want things to sound like.
    Again,great article to help people understand what’s involved in car audio.So many people think you buy any amp and hook all your speakers up and you are ready to go.NOT SO…

  3. Good article but what I want to know is if the efficiency of class D amps allows them to be mounted in tighter areas with less available airflow? I know this is a tough one to call but for instance can you safely mount a class D monoblock sub amp behind a panel in the rear side of an SUV (like some factory amps are?) Or under the floor panel in the back of an SUV where the spare tire is mounted?

    1. Glenn, that’s exactly right and why Class D amps are so compelling. They put out less heat, last longer, and aren’t in need of much passive cooling possibilities like a big and unenclosed space. They do great work in the types of places and situations you mentioned and we recommend them enthusiastically for those reasons.

  4. Quick question , I have two kicker L5’s dual voice coils subs with a 2500w class d monoblock amp can you please post a diagram of how they should be wired please

    1. Hi there, that’s tough to say with high confidence and would strongly recommend that you consult the manual or website of your 2500W amp manufacturer to make sure you do it right according to their amp design.

  5. Good article. I just started using a class D amplifier for my 12″ subwoofer, and I am impressed with the size and the power output. For my front stage components, however, I will continue to use class A/B simply because of the cleaner sound that the older A/B designs produce. While some of the better brands are producing multi-channel class D units with better signal to noise ratio, THD, etc… , Others still need further enhancements in design to keep up with the best A/B class amps in terms of tonal clarity.

    1. Hey Jack, thanks for your feedback here. You absolutely nailed it, in my view. Class D amps are doing some amazing things these days, and they’re starting to also do this for the fronts. I still also focus on A/B personally in my system, but it’s great that tech continues to get better and gives us better choices.

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