In the specs of some audio and video cables, you may have already noticed the letters AWG followed or preceded by one or more numbers to indicate the gauge and diameter. For example, AWG 24 or 28 AWG. But what does AWG actually represent, and what is the equivalent in mm²?
What is AWG or American Wire Gauge?
Also known as the Brown & Sharpe wire gauge, AWG or American Wire Gauge is a unit of measurement used in the United States to determine the diameter and cross-section of a cable. It was introduced in 1857 by J.R. Brown who established 39 steps: from AWG 0000 (4/0) to AWG 36. J.R. Brown’s goal was to standardize the diameter of electric cables so that each manufacturer could provide standardized cables that were easier to identify for the user. It was pretty successful, as most American manufacturers still use this standard today. However, AWG never crossed the Atlantic and the system is unfamiliar to most European users. So how do you determine the diameter and cross-section of a cable according to AWG?
Calculating the cross-section of a cable using AWG
The AWG scale initially featured 39 steps, from AWG 0000 (4/0) to AWG 36. Today, the system reaches AWG 40. The smaller the AWG value is, the greater the cable’s cross-section is. This stems from the fact that AWG represents the number of drawing operations needed to produce a given diameter of cable. The thinner the cable is, the more times it has been pulled through the machine. To help you out, here is a table comparing the AWG and the diameter and cross-section in mm² of cable conductors.
|AWG||Diameter (mm)||Cross-section (mm²)|
The AWG of stranded cables
The American Wire Gauge system is only applicable to circular solid copper conductors. For stranded cables, the space between each conductor implies that the cable’s diameter will be greater than that of a solid cable with the same AWG. Consequently, AWG always indicated the diameter and cross-section of the conductor and not the entire cable. Therefore, if a manufacturer specifies the cross-section of a stranded cable in AWG, it refers to the cross-section of each of the cable’s conductors. For example, let’s look at the Wireworld Chroma 8 USB 2.0 A-B cable which features an AWG of 23 (0.25mm²). As with all USB cables, Wireworld specifies that the Chroma 8 is composed of 4 conductor wires (ground, power, D+ and D-). Therefore, the cross-section of the entire cable is 4 x 0.25mm², not 0.25mm².
Which gauge to choose
The diameter of a cable has a significant impact on the resistance of the conductor. For example, a 2 AWG bare copper conductor has a linear resistance of 0.51Ω/km. This increases to 1361Ω/km for the same material with a 36 AWG cross-section. The gauge should be chosen according to the cable’s function and intended use. When it comes to power cables, the more power a device requires, the greater the gauge of the conductors must be. This is one of the reasons why the power cable on power conditioners must be correctly sized. For example, with its 20 12 AWG (3mm²) oxygen-free copper conductors, the Wireworld Stratus cable is suitable for powering one or several devices up to 18A, or 4000 watts.
The cable diameter is also an important factor when choosing a speaker cable. It is essential when the length of the cable increases because the amplifier “sees” the cable and speaker as a single element. The cable’s capacitance and resistance therefore influence the amplifier’s behavior. A smaller gauge speaker cable is generally more suited to transport high frequencies. However, line loss can be too high from about ten meters. Consequently, it is recommended to use a gauge between 1.5 and 2.5mm² for cable lengths between 1 and 10 metres. Beyond that, a cable with a 4mm² gauge is often preferable.
How insulation influences cable quality
The gauge and the quality of the conductors aren’t the only factors to take into account to ensure the quality of a cable. It should be noted that the cables’ internal conductors are now more exposed than ever to electromagnetic interference generated by the proliferation of electronic devices in our homes. All electrical and electronic devices are likely to generate interference: smartphones, wireless routers, wireless speakers, televisions, microwave ovens, etc. Even simply running different types of cables (power, audio and video cables, speaker cables) alongside each other can cause interference. Their influence on the cables’ behavior and the integrity of the transported signal is an important factor to take into account when choosing any type of cable. Consequently, the amount of interference and its proximity to the cable influence the level of insulation required.
The amount of interference and its proximity to the cable influence the level of insulation required.
If you only need to connect to entry-level devices and the surrounding area is free of electromagnetic interference (no WiFi, no Bluetooth, no wireless telephones etc.), any standard cable with a suitable gauge is largely sufficient. On the other hand, if your installation includes many of the aforementioned sources of interference, it is preferable to choose an optimized and shielded cable.