How do aux cords work?


How do aux cords work?

In: Technology

In what context?

Assuming you mean for some sort of stereo system, the aux cable or aux port allows you to connect your own audio device and use it with the amplifier and speaker system. There is a standard for the type and strength of electrical signal used for stereo systems (called “line level”), so any device with a “line out” port should be able to connect to a “Aux in” port and play music. You can also connect a “headphone out” to an “Aux In” port, but you will have to turn the volume up, since the line level standard is a bit louder than most headphone signals.

Sound is carried as an electrical signal through most simpler audio equipment. Sound is the movement of air many times per second which can be translated to electricity varying many times per second, and that electricity can be used to move a speaker, reproducing those vibrations and therefore reproduce the sound.

For an electrical signal you need a ground, neutral, or “reference” wire – an electrical signal can only make sense or be used when compared to some baseline voltage.

You have one ground then one more active wire to carry a sound signal. But most audio recordings and playback systems including headphones have 2 speakers, left and right. So there is one shared neutral and 2 active signal wires for left/right and that is how the 3 contacts on an aux plug and 3 wires in the cable carry sound for the left and right side.

They have a positive and ground and they are separated on the aux plug by black stripes. Each section is electrically isolated. That is why some aux cords will have 3 sections (one for right speaker, left speaker, and ground) while aux cords for a gaming headset will have a 4th section for a microphone input.

The standard 3.5mm audio connector is one of the simplest standards out there.

The connector you’re familiar with has somewhere between two and five metal segments separated by small pieces of plastic. Each of these segments connects to a wire within the plug or socket. One of these connectors – usually the one at the base of the cable – will connect to the ground. The other connectors often carry some form of audio signal. One of the clever elements is that every element *except* the ground is a standard length – the ring at the top is a certain length, then each subsequent ring is the same, then the one at the very base is however long it needs to be to work. This means that inserting a cable with 4 connectors into one with 3 connectors just sends one of the connectors to ground, and nothing (usually) happens.


To understand how the cord actually sends sound, we need to understand (briefly) sound. At the most basic level, sound is produced when air varies back and forth in pressure. If the sound varies between two levels slowly, it generates a low pitch. If it varies quickly, it generates a higher pitch. There’s more complexities at play, such as multiple different variations on top of each other, but *every* sound can be represented by tracking the pressure over time. The wires in your aux cord carry a voltage, which undergoes the exact same changes as the sound does. The device on the other end is designed to produce pressure in the air around it based on the voltage it receives – which we perceive as sound. The aux cord just carries a voltage from one point to another, and doesn’t do anything fancy. There’s no mechanism to make sure devices are compatible, or to carry digital signals – this is possible, but it requires work outside the cable rather than just being simple.