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When it comes to high-current wiring in a vehicle, there are two types of stranded power wire available: solid copper and copper-clad aluminum. This article looks at the differences between each kind of wire, and explain the challenges of ensuring your high-current device gets the power it needs to do the job you want done.

Car Audio Power Wire: Background

In mobile applications, or anywhere that a conductor may be exposed to movement or vibration, it is recommended to use only stranded conductors. Solid conductors (like single-strand house wiring) may offer slightly more conductor area for a given wire diameter, but over time, the solid wire can work-harden, become brittle and eventually break from repeated back-and-forth motion. Imagine using large-gauge solid copper wires in the wire boot in a door jamb or to your trunk or hatch lid. That is a recipe for disaster.

The term OFC (oxygen-free copper) has become abused and is used synonymously with solid or all-copper conductors. In actuality, OFC is a type of solid copper. When molten copper is cast and drawn into a conductor, the process to make an OFC conductor reduces the oxygen content of the wire. If all is done perfectly, the copper-oxygen content is around 42 parts per million (PPM) vs. a conventional copper with content that is roughly six times that amount.

In the mobile electronics industry, there is no way to know if the solid copper conductor you are purchasing is oxygen-free or not unless you can witness the casting process in person. Everyone in the industry uses “OFC” for a piece of wire that is not copper-clad aluminum (CCA).

Looking at the alternative, we have CCA conductors. In these conductors, the core of the wire is a cylinder of aluminum and around it is a layer of copper. From the side, it looks like copper, but if you cut off a piece and look at the end, you can see the gray aluminum content.

There are further variations. Some companies manufacture all-copper strand wire but coat the outside of each strand with a thin layer of tin to help prevent corrosion.

Car Audio Power Wire: Size

When it comes to flowing electricity, or, more specifically, flowing electrons, the most important thing to consider is wire size. In the mobile electronics industry, we use the American Wire Gauge (AWG) standard. This sets a specific diameter for a conductor. It’s not a debatable number – the conductor either meets the standard or it doesn’t.

Here is where the games begin. There is a second term used in our industry: gauge. In the steel sheet industry, gauge is an important tool for specifying material thickness. In car audio, it means nothing. If you have been around the industry for any amount of time, you will have seen wires that claim to be 0 gauge but have a conductor area equivalent to a 6 AWG. If a wire is labeled as 4 gauge, then sadly, you have no way of knowing how big it is, other than attempting to measure it.

Cutting a wire and looking at the area also doesn’t always tell the story. Some wires are wound quite loosely. This makes the wire very flexible, but does so because there is space around the strands. You sacrifice effective cross-sectional conductor area for flexibility.

Car Audio Power Wire: Materials

In solid copper stranded wire, we ideally want everything to be pure copper. That said, pure copper is quite expensive, even though the cost of pure copper has come down over the past few years; it currently sits at around $2.00–$2.25 a pound on the commodities market. When a manufacturer wants to purchase wire, there are many options: strand count, how the strands and bundles are woven, how tightly they are woven, and so on. Manufacturers also have a choice in the “kind” of copper they make the conductors with. It could be pure copper, recycled copper or a copper alloy. Again, you have no way of knowing unless you are witness to the process.

Don’t let the variations in copper scare you. A solid copper conductor always outperforms a CCA conductor. The biggest challenge with car audio CCA wiring is that it does not, and will not, specify the ratio of copper to aluminum. There are publically displayed measurements of different CCA wire samples where a smaller-diameter wire outperforms a slightly larger wire because it has less aluminum and more copper. Unless you measure it yourself, you just don’t know.

On its own, pound for pound, aluminum has about 60% more resistance to the flow of electricity. When we talk about CCA wire, there is some copper in there; in most cases, the difference diminishes to 30 to 40%.

Car Audio Power Wire: The Challenge

When you look at car audio wiring, there is no way to know what you are getting with a CCA amp kit or roll of wire. Some manufacturers make CCA wire that functions nearly as well as solid copper. In fact, one company makes an oversized CCA that has less resistance per foot than solid copper. The downside is that the wire doesn’t fit into a lot of connectors or terminal blocks. Overall, unless you want to take the time to measure the properties of the kit you are buying, it is better to stick to solid copper.

From the standpoint of long-term benefits, solid copper wire resists corrosion much better than CCA wiring. In climates where road salt or brine is used in the winter to keep surfaces clear of ice, we have seen instances where unprotected CCA power wires have failed completely in less than two years. Why risk the performance of your audio system, when you can simply choose the solid copper wire?

How do you know if you are getting something good? The Consumer Technology Association (formerly the Consumer Electronics Association) has developed a standard for wiring. It is called CTA-2015 (formerly CEA-2015) specification. It describes the minimum standards for wiring for use in mobile electronics applications. The standards include that the wire must be stranded solid copper, the minimum number of strands for a given AWG wire size, and the area of the wire and its maximum resistance. If you stick to the brands that support the CTA-2015 standard, you should never have any problems.

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.

For decades, car audio enthusiasts have been fiddling around with the gain control on their amplifiers in hopes of “getting more out of them.” Many professional installers have scientific, repeatable processes in place to ensure these controls are set to provide the maximum performance and reliability from your audio system. Let’s look at the most misunderstood, and most often adjusted, control on car audio amplifiers – the gain control.

What Is a Gain Control?

When a manufacturer decides to develop an amplifier, they need to decide how many channels it will have, how much power it will produce, what additional features it will include and what source units it will work with. Because modern source units have maximum preamp output voltages that range from 1.7 to 5 volts, amplifiers have to be adjustable to make their full rated power when driven with these signals.

Let’s make up an example: Imagine a 100 watt mono amplifier that was designed to produce full power (100 watts) when it receives 2 volts of audio signal. This is a reasonable amount of signal gain, but leaves us open to two significant problems. What if we want to use this amplifier with a source unit that can only produce 1.7 volts? We can’t get the amplifier to full power even with the volume control on our radio turned all the way up. In fact, we only get 72.25 watts out of our amplifier. On the flip side, if we have a source unit that can put out 4 volts of signal, then the amp would attempt to make 400 watts with our fixed gain setting. Since the power supply of the amp was only designed to provide enough voltage to produce 100 watts, the signal would be severely clipped and distorted, and there is a great chance that the amplifier and your speakers might be damaged.

The Solution

For a single amplifier to work with multiple sources, amplifier manufacturers have to make the input signal level adjustable. We call this the gain or sensitivity control. It doesn’t adjust how much power the amplifier will make, but it does adjust how much of the input signal the amp uses to make full power.

There is a secondary reason for adjustability: Not every speaker has the same sensitivity. This means that sometimes you have more power than you need. Let’s say your front speakers produce 90 dB of output from 1 watt of power, but your rear speakers are much larger and produce 93 dB of output from the same 1 watt of power. For them to appear to be of equal loudness at the listening position, we only need half the power to the rear speakers. We turn down the sensitivity of the rear channels of an amplifier to balance these out.

Making Gains (Using Your Gain Control!)

Your installer may use one of many different processes to adjust the gain controls of your amplifier. We want the gain controls to be as low as possible, but still allow you to get full power from the amplifier. Why do we want the gain low? That is, perhaps, the fundamental key to this article.

We want the amplifier to accept an input signal with as much voltage as possible for it to produce full power. Having more voltage on your interconnect cables helps drown out noise. Less amplifier sensitivity (lower gain setting) also helps to reduce noise. When the amplifier gains are set properly, you get full power from your amp without unnecessary hiss or background noise.

There are four common methods for adjusting gain controls: by ear, with a small amplified speaker, with an oscilloscope or with a distortion detection device. Setting by ear with music is very difficult and can lead to inconsistent settings. That being said, if your installer uses a test tone, the “by ear” process can work quite reliably. Using a small amplified speaker is similar to that process – there is a test tone, but the small speaker allows your installer to check the preamp signal from the source unit, and in and out of any signal processors.

Using an oscilloscope to set an amplifier’s gain control is one of the best ways to get an accurate reading. Oscilloscopes work for any frequency, so they are very flexible. Your installer can see exactly when the amp has reached its peak voltage.

Finally, companies like D’Amore Engineering and SMD have developed products designed specifically for mobile electronic installers to check for signal distortion on preamp or speaker signals. All you have to do is plug the device in and turn it up until the red Distortion LED comes on. Bam – done! A word of warning on these devices, though: They are very accurate and can detect distortions other than signal clipping. Many product design problems have been found when attempting to set gains with these.

How Can You Check Your Gains?

If the sensitivity controls on your amplifiers are set properly, you should be able to get your amplifiers to distort a little bit with the source unit at full volume. If you are wondering why a properly set amplifier will distort, that’s a great question. It’s called gain overlap. We want to have a little extra sensitivity in case we are playing a song that is recorded quietly. A great example of this is the well-known “Brothers In Arms” album by Dire Straits. It needs a good 5 extra dB of gain to get rocking. In fact, the original 1985 release from Warner Brothers Records had several songs where the loudest part of the song was below -5 dB. “Why Worry” has a peak level of -13.27 dB. A nightmare for an installer trying to set gains, but, luckily, that’s not a song most people rock out to.

If you can’t turn your volume control past halfway without your amplifiers running out of power (distorting), then it’s time to visit your local mobile electronics specialist. Likewise, if you hear a significant amount of hiss at low volume levels, then you likely need an adjustment.

Properly set gain controls won’t make your system quieter, and turning up the sensitivity doesn’t make your amplifier more power. Gain controls exist to ensure that your system is always working the best it can. Please leave them alone, or ask your installer about how they are set.

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.