In this case, a 100 watt amplifier is really drawing about 200 watts of power from the source.īased on this information and assuming an average vehicle charging voltage of 13.8 volts, the current draw of a typical Class AB amplifier can be determined as follows This means only about half of their power is actually turned into audio output and the other half is turned to heat. 75 ÷ 13.8 = 9.7 amps.Ĭlass AB amplifier - On average, a Class AB amplifier is only about 50% efficient. Total RMS (100 watts) ÷ Amp efficiency (75%) ÷ Source voltage (13.8 volts) = Amperes of current draw or 100 ÷. If used hard enough or long enough, they can even get hot to the touch.īased on this information and assuming an average vehicle charging voltage of 13.8 volts, the current draw of a typical Class D amplifier can be determined as follows The other 25% is soaked into the heat sink of the amp which is why they get warm after being used and the harder and longer we use them, the warmer they get. What does that mean? That means in order for a Class D amp to make 100 watts RMS power it actually will draw about 133.33 watts of power from the power source (battery, alternator) and the wiring needs to be able to handle that draw.

By simply multiplying the number of channels it has by the RMS power per channel you can determine the total RMS power.Ĭurrently there are many types of amplifiers but really two are used the most - Class D and Class AB - and each has a unique formula to calculate current draw Ĭlass D amplifier - The average Class D amplifier is about 75% efficient. To approximate the current draw (amperes) of the amplifier, you need to know its total RMS power. How do I know which size wire to use? The size of the wire is determined by the current demand of the amplifier and the length of the wire run itself. Why is wire size so important? Because an amplifier needs the correct size power and ground wiring in order to operate reliably and at its full potential. What is the Right Gauge for My Amplifier?Ĭhoosing between 4 gauge vs 8 gauge wires or other cable sizes should be easy if you consider voltage drops and amplifier ratings.A question we get asked here at Streamline Audio on a pretty regular basis is “what size wire do I need for my amplifier?” This is a very important question since using the correct wiring with any amplifier is critical to the amps performance. The lack of current makes the car amp operate at suboptimal conditions. This produces a voltage drop at the part of the amplifier and may cause a lack of current flowing through the amp. The longer the wire, the greater the resistance will be. This resistance is caused by electrical charges hitting atoms in the wire.

Any conductor has inherent resistance within them. The last thing we need to know is the length of wire to be used for amplifier connections. Thus, if we have higher powered devices like a 2500 watt amp, they will need thicker wires, while a small 200 watt amp may need thinner wires. Thicker wires, thus lower gauge numbers, have greater current carrying capacities, since they allow more electrons per unit length. Wires may be classified from 0000 gauge (4/0 gauge) with a diameter of 0.46 inches (almost half an inch) down to 40 gauge with a very thin diameter of 0.0031 inches. The lower the number, the thicker the wire. The second thing we need to know is the gauge of the wire, expressed in American Wire Gauge based on thickness. Using this relationship, we can determine the wire gauge based on the amperage of the amplifier.Īlso, we may generally expect larger current draws for 3000 watt amp units, and lower draws for weaker devices like a 1000 watt amp or a 1500 watt amp. Thus, we rearrange our formula to include the efficiency of the car amp to get: Class AB amps have efficiencies of around 58%-65%, while Class D amps have higher efficiencies of around 69%-80%. The next thing we have to know is the efficiency of the car amplifier.Ĭar amplifiers are commonly categorized as Class AB or Class D.

Gauge wire for amplifier