Power amplifiers boost line-level signals from processors or preamps to speaker-level signals and pass them through the speakers.
Most power amplifiers have multiple channels. An example is the stereo amplifier that has both right and left audio channels. However, some amplifiers have only one channel.
These monoblock amplifiers outperform multichannel amplifiers. As a result, they are common in-car audio systems and require tuning. In this article, we’ll show you how to tune a monoblock amp.
How To Tune A Monoblock Amplifier
You can tune a monoblock amplifier manually or with a multimeter. We’ll walk you through both methods.
This method is straightforward and cost-effective. It requires no special tools or skills. However, you must be careful not to miss some distortions. Follow the steps below to tune your monoblock amplifier manually.
- Lower the gain and disable any special settings or filters.
- Gradually raise the volume of your car stereo until you hear distortions. Then lower the stereo volume to find the sweet spot.
- Adjust the gain using the same method above. Turn it up gently. Don’t reduce the gain by more than 80% when you start hearing distortions, so you don’t damage your speakers.
- Enable any required special settings or filters.
- Repeat steps 2–3 until you find the sweet spot. If you’ve correctly tuned your monoblock amp, you should play at 80% volume without any distortions.
- If you notice distortion, isolate the speakers causing it and reduce their gain until you get good sound.
Tuning with a multimeter
This method is a more advanced procedure. Follow these steps to tune your monoblock amp with your multimeter successfully.
Measure your speaker’s impedance using a digital multimeter: To do so, you should take the following steps:
- First, turn off the speaker power.
- Next, find the negative and positive terminals.
- Next, connect the multimeter’s black probe to the speaker’s negative terminal and the red probe to the positive terminal.
- Finally, record the multimeter’s impedance.
Compare your speaker’s impedance with your amp’s wattage: Here’s how to do it:
- First, consult your amp’s user manual for the recommended wattage output.
- Then, compare the recommended value with the speaker’s impedance.
Determine the target AC voltage: Using the formula V = (P x R), calculate the output voltage required to set the amp’s gain. P stands for power and R for speaker impedance. Note the figure as you’ll need it later.
Disconnect all connected accessories: Unplug the speakers, subwoofers, and other extras. To make things easy, you can disconnect only the positive terminals.
Adjust equalizer to zero: Set the equalizer to 0 dB or even turn it off.
Adjust gain to zero: Most monoblock amps have a dial that you can turn counterclockwise to achieve this. At this point, only the power source should remain connected to your amp.
Adjust max volume to 80%: Set the head unit to about 80% of max volume.
Use a test tone CD: It helps if you play a 60 Hz test tone CD on the stereo. While it’s playing, gradually turn up the amp’s gain knob until the multimeter reads the output voltage you calculated.
Reconnect all disconnected accessories: Double-check that all wire connections are in place before turning on your speakers.
What Is Speaker Impedance?
Speaker impedance is the “resistance” a speaker provides to an amplifier’s current. We refer to this resistance as impedance because an amp’s output current is AC (rather than DC).
The impedance of a speaker indicates how much current will flow through it at a given voltage. Therefore, a speaker with a lower impedance can handle higher power.
However, this is correct until the amp’s current and power output reaches a limit. Then, the amp fuse will either blow, the amp will die, or the amp’s protection circuit will turn the amp off at this point. As a result, never use an amp with load impedance lower than the specified minimum.
An Overview Of The Monoblock Amplifier
A mono amplifier is a single channel amplifier designed to reproduce low-frequency sound, like a subwoofer’s deep bass. The monoblock amplifier only has one channel and sends one audio signal to each speaker.
A monoblock amplifier is sufficient for one audio channel system. However, to play in stereo, we need two monoblock amplifiers (or a stereo amplifier).
We could use three monoblock amplifiers, a stereo amp, a monoblock subwoofer amp, or an all-in-one amplifier that can drive a 2.1 setup.
Applications Of The Monoblock Amplifier
A monoblock amplifier will power a single channel speaker in most car and home audio systems. The monoblock amp produces a single signal, ideal for a subwoofer’s low-frequency design. In addition, two subwoofers can connect to a single mono amp for efficient performance.
A mono amp is not ideal for stereo music since it can only transmit one audio signal. Alternatively, a mono amp can power a single signal speaker, such as a subwoofer that produces sounds in the low-frequency range.
Monoblock amps come in different classes, each distinctive design and operation to give the desired result. In the next section, we’ll examine other types of monoblocks and how they work.
Classes Of Monoblock Amplifiers
There are two classes of monoblock amplifiers, the class AB and the class D monoblock amplifiers. Let’s consider them one after the other.
Class AB monoblock amplifiers: Most quality amplifiers are Class AB. The line-level input signal triggers these amplifiers. Each time the amplifier detects a signal, it allows a small amount of power from the power supply. Even when there is no signal, AB amplifiers keep some energy flowing to the switching device.
This design combines the sound of a Class A amplifier with the sound of a Class B amplifier. A monoblock amplifier has one input, one power supply, and one amplifier circuit.
Class D monoblock amplifiers: These monoblocks have one channel but work differently than Class AB amplifiers. They use a fast-on/fast-off power supply to simulate the input signal’s waveform. Class D monoblocks are smaller and require less power than class AB amplifiers due to the rapid switching. However, some audiophiles complain about their sound quality.
Benefits of Monoblock Amplifiers
Monoblock amplifiers have two advantages over multi-channel amps. First, there’s no risk of channels mismatch that can potentially distort the sound. Secondly, the dedicated power supply provides the necessary amplification power for the single channel without splitting it with other media.
Drawbacks of Monoblock Amplifiers
Because each monoblock amplifier is a standalone unit, setting up a monoblock system is usually much more expensive than with multichannel amplifiers. It also takes up more space and requires more wire routing since each amplifier has a separate power cord.
How To Install A Monoblock Amplifier In Your Car
Follow the simple instructions below to connect a mono amplifier to a subwoofer.
- Disconnect the car battery negative terminal.
- Run a power wire from battery to amplifier through the firewall. It’s also possible from the cabin to the engine. It’s up to you which way is more comfortable or easier to reach the wall.
- Trim the power wire and install a fuse near the battery. The main fuse should be under the hood for safety.
- Connect the amplifier to the battery’s ground wire. Many people use any chassis connection in the trunk area for ground, but this increases resistance and reduces power from your amplifier. The ground wire and the power wire should have the same gauge as the power wire. When it comes to power, both are equally important.
- Connect the head unit to the amplifier with a signal wire. Signal wires should be on the opposite side of the car as power wires. In any case, you don’t want to hear engine noise in your speakers after installing a new amplifier.
- If your mono amp has a remote, connect it. You can run remote wires alongside signal wires. That way, you can change the bass without opening the trunk.
- Connect the remote and signal wires to the amp.
- Next, wire an amplifier’s power and ground. Use wire gauges that match amplifier ports.
- Set your monoblock in place and secure it. Assemble the amplifier in a well-ventilated area, especially if it is A or AB class. For example, a powerful amplifier may need vertical installation in a trunk rather than horizontally for better ventilation. Also, secure it, so it doesn’t move in the trunk when you brake or turn.
- Make this connection as short as you can. For example, rather than using 4-foot speaker wires, create a longer power connection and even screw an amplifier to the enclosure.
- Reconnect the battery to your car’s chassis. Reconnect the battery to the primary ground wire if necessary
- Start the engine and check the amplifier. Start slowly and gradually increase the volume. Set up your amp and adjust the high and low pass filters. Also, if you’re using a crossover, you can now experiment with all possible settings.
A mono amplifier is a single channel amplifier that reproduces low-frequency sound, like a subwoofer’s deep bass. The monoblock amplifier only has one channel and sends one audio signal to each speaker.
These monoblock amplifiers outperform multichannel amplifiers and are common in-car audio systems.
You can tune a monoblock amp in two ways – manually or using a multimeter. In the manual method, you adjust the gain and volume settings until you find a sweet spot. Using a multimeter involves determining parameters such as impedance and wattage and adjusting adequately.