What Is a Monoblock Amp, and How Does It Work?

Many audio enthusiasts want to know, what is a monoblock amp, and how does it work? A monoblock amplifier is a single unit that amplifies only one channel. A monoblock amplifier uses special components to strengthen a single channel rather than sharing multiple channels. As a result, it has grown in size, weight, and cost.

In reality, a monoblock amplifier is used to amplify single signals from audio systems. The available audio channels determine the number of monoblocks required. For example, only one monoblock is required if you only have one audio channel. Three monoblocks will suffice if you have a stereo pair of speakers and a subwoofer to handle the low end.

How Does a Monoblock Amplifier Work?

Power monoblock amplifiers can be measured using a digital signal meter, similar to the one used by a preamplifier, and then powered up to drive speakers.

Most power monoblock amplifiers are built into receivers or have multiple channels. For instance, a stereo amplifier works with the right and left channel signals, and some exceptions only have one channel. These “monoblock” amplifiers outperform regular multichannel amplifiers in terms of performance.

What Is a Monoblock Amp? Difference Between Monoblock Amplifiers and Stereo Amplifiers

The difference lies in the channels, where there are two independent channels within a single chassis to handle stereo amplifiers’ left and right audio. These amplifiers also use a single shared power supply instead of monoblock amplifiers that use separate power supplies.

Types and Benefits of Monoblock Amplifiers

Class-AB Monoblock Amplifiers

Most high-quality amplifiers employ a Class AB design. The line-level input signal acts as a trigger in these monoblock amplifiers. When the amplifier detects a signal, the power supply’s power can pass through.

Even with little to no signal passing through it, AB amplifiers keep a small amount of power flowing out to the switching device. This design combines the cleaner sound of a Class A amplifier with the less accurate but more energy-efficient noise of a Class B amplifier.

Working Mechanism

A monoblock amplifier has a single input, power supply, and amplifier circuit that feeds a single amplifier. A pull-push force of output transistors in a Class AB monoblock amplifier is on more than half of the time and does not turn on and off abruptly.

This gives the amplifier the characteristics of a Class A amplifier when the signals are low power and a Class B amplifier when the power is high. There is an optimum bias current for each amplifier that minimizes the crossover distortion of the Class B design.

Class AB amplifiers have much higher efficiency than Class A amplifiers, up to 50%, and much less distortion than Class B amplifiers. Most home theater and stereo amplifiers are Class AB.

Benefits of Using Class AB Amplifiers

Until recently, the only practical option for achieving high-fidelity, full-range amplification was to use an AB amp. Still, Class D amps that are just as accurate are now being built, but Class A remains the winner in terms of accuracy.

Class AB amplifiers combine the best characteristics of their combination (A+B) while attempting to minimize the drawbacks. Class AB amplifiers allow current flow through the output transistors like Class A amps.

The main difference between AB amps is that they only allow a lower level of electricity when not in use. As a result, Class AB amplifiers can maintain higher levels of audio fidelity than Class A amplifiers while remaining cooler and more efficient than Class B amplifiers.


The conduction angle in a Class AB amplifier is intermediate between Classes A and B, as each of the two active elements conducts more than half of the time.

This class of amplifiers is regarded mainly as a good compromise for amplifiers because, for the most part, the music signal is quiet enough to come out crisp with little distortion.

You can use negative feedback to reduce crossover distortion even further.

Operations of Class AB Monoblock Amplifiers

Class AB amplifiers switch operations for small and more significant current outputs to minimize the problems arising from its parents’ low efficiency and distortion. When the current output is low, these amplifiers operate as Class A and vice versa.

The compensation between the two waveforms reduces the “saturation zone.” Combining the two waveforms also reduces the amount of crossover. No current passes through these amplifiers when there’s no signal, which is good. Most electrical devices experience damage from excessive heat, but a halt in current flow prevents thermal runaway, ensuring durability.

Class AB amplifiers select a specific quiescent current to maintain the heat dissipation level, which is adjustable depending on the current temperature of output transistors. For instance, a circuit is built with diodes that are physically close to the output transistors and are specified to have a matched temperature coefficient. Another method for thermally tracking bias voltages is to connect small resistors in series with the emitters.

Even though Class AB amplifiers function better than their predecessors, they still sacrifice about 40% of their efficiency to remain linear. Class A, B, and AB are known for their linearity because the input signal amplitude and output signal amplifiers are correlated.

Class D Monoblock Amplifiers

Class D monoblock amplifiers have a single channel, but they operate very differently than Class AB amplifiers. Instead of having an always-on power supply, they rapidly switch the power supply on and off to simulate the input signal’s waveform. These amplifiers were developed in the late 1950s and have gained popularity in recent years.

This rapid switching makes them highly efficient, allowing Class D monoblocks to be much smaller and less power-hungry than traditional AB amplifier designs. On the other hand, some audiophiles believe that their sound quality is inadequate.

Class D car monoblock amplifiers are common audio power amplifiers that use a more efficient amplifier based on pulse width modulation technology. Contrary to some misleading or misunderstood descriptions, these amplifiers are not “digital amps.” Instead, they continue to work with analog signals, albeit differently.

Due to technological and sound quality limitations, they were only used for powering subwoofers because the inferior sound quality they offered wasn’t noticeable in the low-frequency range ofbass in music.

Thankfully, car audio technology and electronics have advanced significantly. A wide range of Class D amps are now available to drive full-range speakers and subwoofers, and all are from a single small amplifier.

Class D Amplifier Working Mechanism

Class D amplifiers’ design makes them more efficient than Class A, B, and AB by reducing the problem of power dissipation. These amplifiers achieve this by switching the on/off signals depending on the input level, forming a series of voltage pulses.

Power transistors then drive these signals, which then amplify them. The amp’s switching power supply amplifies the square wave signals to a higher voltage, allowing them to deliver amplified power to the speakers.

The switch in voltage pulses is relatively rapid, which gives your transistors a chance to rest frequently, reducing power dissipation and wastage. Once your amplifier receives the signals, electronic circuits now streamline the voltage pulses, amplifying them into a better version of the original amplified signal.


Class D amplifiers consist of filters right before the speaker output terminals that perform a final sweep on the output signals, removing any high-frequency disturbances, making it smaller than the audible range. These amplifiers are unique because, unlike the rest, they consist of a special integrated circuit that makes the final edits to audio signals directed to them.

Smaller Class D amplifiers come as “all-in-one” products that directly drive the speakers. These are typical in computer speakers or tiny home stereo monoblock amplifiers.

Class D amplifiers employ some form of pulse width modulation to control the output devices. Each device’s conduction angle is no longer directly related to the input signal but varies in pulse width.

Instead of linear gain devices, the active devices, like resistors and transistors in Class D amplifiers, function as electronic switches that are either on or off. Before being applied to the amplifier, the analog signal is converted to a stream of pulses that represents the signal using pulse density modulation, delta-sigma modulation, PWM, or a related modulation technique.

Benefits of Class D Monoblock Amplifiers

Class D amplifiers have a higher power efficiency and reduced risk of thermal runaway, increasing their popularity. The final voltage pulses have a fixed amplitude, and the switching elements are typically a metal-oxide-semiconductor field-effect transistor.

The vacuum tubes and, at one time, bipolar junction transistors are non-linear, meaning they’re either on or off depending on the presence of power passing through.

When entirely on, metal-oxide-semiconductor field-effect transistors (MOSFETs) have the lowest resistance and, as a result, even less power compared to other amplifiers. Compared to an equivalent Class AB device, the lower losses of a Class D amplifier explain their small heat sinks.

This reduces the input power required and allows for a lower-capacity power supply design. As a result, Class D amplifiers are typically smaller than Class AB amplifiers.

Another merit of the Class D amplifier is that it can operate from a digital or analog signal source without first requiring a digital-to-analog converter to convert the signal to an analog form.

Suppose the signal source is digital, such as in digital circuitry. The binary digital signal can be converted directly to a pulse width modulation signal applied to the amplifier, greatly simplifying the circuitry.

A Class D amplifier with a moderate output power can be built using a standard complementary metal-oxide-semiconductor logic process, making it suitable for integration with other types of digital circuitry. As a result, it is commonly found in a system where the circuit is integrated with audio when the monoblock amplifier shares a die with the central processor.

Class D amplifiers are commonly used to control motors, but they can also be used as power amplifiers. However, if the signal is not already in a pulse modulated format before amplification, it must be converted first, which may necessitate the use of additional circuitry.

Switching power supplies have even been converted into crude Class D amplifiers, though these typically only reproduce low-frequency signals with acceptable accuracy. You can now find better non-linear audio power amplifiers on the market.

These designs are arguably better than the traditional AB amplifiers out there. Class D amplifiers were first used in automobiles as high-power amplifiers.

These amplifiers are also smaller because of the reduced sizes of their heatsinks and cooling fans. They’re also considered high efficiency because these amplifiers have longer battery life when dealing with the problem of heat dissipation.

General Benefits of a Monoblock Amplifier

Monoblock amplifiers are pretty popular because each chassis only has one channel. They are also known as one-channel amplifiers.

Monoblocks are superior in terms of power amplification. Because they only have one channel, all power is dedicated to it. Monoblocks produce higher-quality sound and provide reliable power to the channel. There is no power-sharing between channels, so there is less muddying of the sound.

Final Thoughts

So, what is a monoblock amp? It’s essential to have the correct information, especially for a big purchase such as an audio system for your car or home. This article covers what a monoblock amplifier is, its subcategories, and the benefits of each segment.

The best advantages of Class AB and Class D depict the excellent qualities of a monoblock amplifier. They produce superior power amplification, which explains why it’s recommended over the other types of amplifiers. This type of amplifier is applicable widely.