To close out our series of educational articles on amplifier specifications, we are going to talk about operating voltage limits and, by association, the protection circuits built into a car audio amplifier. In the good old days of electrical systems that were composed of an alternator, battery, switches and a couple of relays, delivering a relatively constant voltage to a car audio amplifier was easy. New technologies and limits on battery, alternator and wire size have made it much more difficult to keep our amplifiers happy.

Automotive Start-Stop Systems Cause Low Operating Voltage

With the never-ending battle to eke out every ounce of fuel efficiency from the vehicles we drive, automakers have resorted to systems that will shut down the engine to save fuel while idling. Transitioning from standard idle mode to the shut-down state doesn’t pose a problem for most amplifiers as the battery voltage only drops to the 12.2 to 11.5-volt range. If the voltage starts to drop because the car has been idling too long, the engine will restart automatically.

What poses a problem for modern car audio amplifiers are the voltage dips associated with the engine starting. In conventional vehicles, the stereo is off while you are starting the vehicle. These start-stop systems keep everything running and playing as the engine restarts. Electrical system voltage can drop below seven volts while the engine cranks. Many amplifiers shut themselves down below nine or ten volts, and as such, your music would stop playing. While a pause in your music isn’t truly problematic, it can be annoying if you are stuck in stop-and-go traffic.

New amplifier designs include circuitry that will keep the amplifier active during brief low operating voltage conditions. Some companies specify their amps as being able to handle as little as 6 volts for as long as 5 seconds to ensure that your music plays without interruption. This same start-stop compliance design is required for digital signal processors to prevent them from shutting down during engine restarts.

Car Audio Amplifier Protection Circuitry

Three decades ago, if you shorted the outputs of an amplifier, it would blow up, occasionally with spectacular results. Modern amplifiers include protection circuits that monitor different functions and automatically shut the amp down when an unwanted condition occurs. Most amplifiers include protection against overheating or short circuits on the speaker wires. Better amplifiers may provide a warning if a power connection over-voltage condition occurs that could damage the components inside the amp.

A select few manufacturers provide computerized monitoring of different parts of their amplifiers and flash error codes to let users know why the amp is in protection. Short circuits, over-voltage, under-voltage, over-temperature on the power supply and output stage and a notification about repeated short circuits are provided. This information makes it much easier and more efficient for a technician to troubleshoot an installation or speaker issue.

How Car Audio Amplifiers Handle Over-Temperature Conditions

There are two ways for an amplifier to protect itself if it gets too hot. The most common mode is for the amp to stop playing music so that the power supply and output switching devices can cool off. The second option is for the amp to reduce the output signal so that less heat is created. While it’s nice that your music won’t stop playing, most consumers tend to try and turn the volume up higher when the music gets quieter. Eventually, amplifiers that roll back power will go into a state of full protection and shut themselves down to protect components.

If you live in an area that gets hot during the summer, choosing an amplifier with adequate cooling from a large heatsink or a fan is a good idea. Cramming a tiny little amp into the corner of your trunk or cargo area may not be the best choice in this situation.

Visit Your Local Mobile Enhancement Retailer Today

If you are interested in upgrading the audio system in your car, truck or SUV, purchasing a new amplifier will be a fundamental part of the process. Your local specialist car stereo shop can help you wade through the hundreds of amplifier options on the market to find a solution that sounds amazing and works with your budget and performance expectations.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

If you are thinking about having your local mobile enhancement retailer add a subwoofer amplifier to your car or truck, you may want to ask them about the remote level or bass boost control options that are available. Being able to adjust the amount of bass your system produces from the driver’s seat allows you to fine-tune the system for the music you are listening to or your mood. Let’s look at five of the most popular options available to adjust the output of a new subwoofer system.

Dedicated Remote Level Control

Many subwoofer amplifiers have a built-in jack that your installer can connect to an included (or optional) remote level control. In most cases, these are RJ11 jacks, similar to what home phones use. The remote includes a long cable that can be run to a location on the dash or center console where the knob or control panel can be installed.

How the remote works is important to the overall reliability of your sound system. To prevent distortion from clipping, the remote should ideally only serve as an attenuator. Your installer will configure the system to produce maximum power from the amp with the level control turned up all the way, then you can turn it down to suit your listening preferences.

Digital Signal Processor Remote Controls

Almost all DSP manufacturers offer some sort of remote control that is compatible with their processors. These remotes can serve as master volume controls or subwoofer level controls and can usually select different presets if the processor supports that function. Whether the processor is a stand-alone system or integrated into an amp, adding a remote is a great choice.

Some processors have provisions to add a remote control that can be assigned to specific channels and operate over a specific range. This remote can be configured to act as a level control for a subwoofer, a center-channel speaker or rear speakers, depending on how the system is configured. This style of remote can also serve as a master volume control for the amplifier in instances where you are not using a radio with a volume knob as a source. This single knob is often easier to use and much less expensive than a full controller.

Remote Bass Boost Controls

Some inexpensive amplifiers come with a remote bass boost control. These controls work in the same way as the adjustment potentiometer on the side of an amp to apply a narrow EQ band of signal boost to the audio signal.

There are two problems with bass boost controls. First, they increase the output of the amp, so your system needs to be tuned with the control at its maximum setting. This configuration makes it difficult to blend the sound of the subwoofer with the mid-bass speakers. Secondly, using large amounts of boost often sounds unnatural. Boosting the region around 45 or 50 Hz is a lot of fun, but the audio information down at 25 and 30 Hz and up at 70 to 80 Hz is just as important. Ideally, a remote level control is a much better choice than a bass boost control.

Source Unit Subwoofer Level Controls

If you have upgraded your sound system with a new radio or multimedia receiver, most include a subwoofer output level adjustment in the audio configuration menu. It’s worth noting that these radios typically don’t produce their maximum output signal on the subwoofer preamp connections unless the subwoofer level control is at its highest setting.

Many years ago, a radio manufacturer placed a rocker switch on the front panel of one of their radios that provided direct access to the subwoofer output level. This was a truly genius idea! These days, you have to press a few buttons or navigate a menu option or two to access the adjustment menu.

Integration Processor Level Controls

Many audio integration processors and converters (often called Line Output Converters or Line Level Converters) have an option for an external remote level control. Depending on the design of these processors, the output controlled by the knob could be paralleled off of a single stereo input, or be from a second dedicated input. If your audio system needs a processor to take the signal from the factory radio or amplifier and turn it into something the amp can use, look for something with a remote level control.

Upgrade Your Car Audio System Today!

Upgrading an existing subwoofer or adding one to your factory car stereo is the most dramatic improvement you can make to your mobile audio system. Alleviating the need for the small speakers in your doors, dash or rear parcel shelf to try to produce bass makes them sound better, play louder and last longer. Drop by your local specialist mobile enhancement retailer today to find out how you can add a subwoofer enclosure and amplifier with remote level control to your car stereo system.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

We are at our second-to-last article in our car audio amplifier specification series and this time, we are going to talk about Class AB amplifier crossover distortion. This distortion has nothing to do with the high- or low-pass filters built into your amplifier; it’s a problem with the very concept of the Class B amplifier topology. Don’t fret — we’ll explain what causes it and how it’s minimized to a level of near inaudibility.

How Do Class AB Amplifiers Work?

Before we can explain what crossover distortion is, you’ll need a basic understanding of how the output of a Class AB amplifier works. In a Class A amplifier, a single transistor (or bank of transistors) takes care of controlling the voltage going to the speaker. When no signal is being produced, the transistor is set at a 50% output level (and gets VERY hot). As the alternating current (AC) from the signal source passes through the amp, the output voltage goes up and down until it reaches the maximum or minimum possible level associated with the transistor being off or at its maximum output level.

In a Class B amplifier, we use one transistor to handle the positive half of the waveform and a second transistor to handle the negative half. The primary advantage is that when there is no signal present, both devices are almost completely turned off and very little power is consumed.

The Class B topology is where our crossover distortion problem arises. As the audio signal swings from positive to negative, it needs to switch from one device to the other without any issues. It’s at this point where the signal crosses over from one device to the other that problems can happen — hence the name, crossover distortion.

Amplifier designers who truly care about the sonic qualities of their products know how to handle this transition and can effectively eliminate crossover distortion by biasing the positive and negative output devices into their active regions. While this does create a little more heat, it reduces distortion dramatically. This is where the Class A part of an AB amplifier comes from: The devices are turned on a little bit (like a Class A amp), but for high-level signals, act in a Class B configuration.

 

Why Does Crossover Distortion Matter?

At low output levels, even in moderate-quality Class AB amplifiers, crossover distortion is more prevalent than when an amplifier is producing very low amounts of power. More accurately, the effect of crossover distortion decreases as the output level increases.

Let’s look at the distortion characteristics of three different amplifier topologies to gain a better understanding of that statement. Up first is our truly outrageous low-quality four-channel amplifier. This workhorse of mediocrity has served us well through this series in explaining the kind of harmonic distortion versus its output level.

For a stark and dramatic contrast, we’ll switch to our high-end amplifier. This amplifier is unique in that it uses a high-bias design intended specifically to reduce crossover distortion in the transition between the positive and negative output devices. The graph below shows the distortion of 0.09% versus the output level.

Choosing the Right Amplifier for Your Audio System

If the goals for your audio system are world-class performance, and you intend to use Class AB amplifiers, you can reduce the effects of crossover distortion by matching the power requirements of your speakers with amplifiers that will operate higher in their output range. For example, if you want a 150-watts-per-channel amp for your mid-bass drivers, you may only need a 50-watt amp for your midrange speakers and a 10-watt amp for your tweeters to achieve the same acoustic output level. BestCarAudio.com published an article on speaker power handling that explains why.

While you can’t always choose high-quality amplifiers with extremely low power levels, you can minimize the effect of crossover distortion by not using a monster amp on your tweeters. Your local specialist mobile enhancement retailer would be happy to design and install an amazing car audio system upgrade — drop by and talk to one of their Product Specialists today!

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.