Lesson 11

Analog Audio Cables

There’s so many different types of audio cables. having a firm understanding of the different types of signals, which a are
- balanced, unbalanced, stereo, mono, and how the various cables carry each signal is crucial for fixing cables, building custom cables, troubleshooting signal flow issues and finding where a buzz is coming from.

To understand cables, first you need to understand how audio flows as electricity. Any electric current needs to have 2 conductors, one for positive and one for negative charges. In audio, 2 wires are needed to carry a single channel. the 2 wires are often called a signal wire, and a ground wire, or positive and negative. If there are multiple channels of audio, all the channels can share the same ground, but each individual channel must have its own dedicated signal wire.
In a shielded cable, the ground wire surrounds the signal wire, and acts as a shield, blocking interference. A non shielded cable will simply consist of the wires running together down the middle.

A stereo cable carries 2 channels of audio, a left and right, and will consist of 3 wires.
The ground, which is shared among both channels, is usually wrapped around the signal wires to offer shielding. And inside the ground wrapping will be the 2 signal wires for each channel.

A stereo cable will usually have a 1/8” jack or a 1/4” jack. These 2 jacks serve the exact same purpose, and there is no difference in sound quality between them. The reason 1/4 is usually used in pro audio is because it’s more durable, and often gets a better connection, so there’s less likelihood of having a poor connection which can result in pops and clicks.

An xlr cable carries a single channel of balanced audio. Balanced audio uses 3 wires to carry 1 channel of audio, and the additional wire helps with rejecting interference.
The way it works, is it has 1 ground, which acts as a shield in its usual way, and it uses 2 signal wires. These 2 signal wires are in opposite phase, so any interference that is picked up, will enter both these wires in equal amounts, and in the same phase. When the cable reaches its destination, one of the signal wires is changed polarity, and then blended back into the other one. When they are blended back together, any interference that was induced into the cable will be of opposite polarity and there fore cancel itself out.

Xlr cables are used to for both microphone level signals, and line level signals. 

1/4” balanced cables are the exact same cable as an xlr, just with different connectors. This connector has 3 parts, called the tip, ring and sleeve, and is therefore commonly called a TRS. The tip and ring are carry the signal, and the sleeve is the ground. A 1/4” cable usually carries a line level signal, which can be either a single channel balanced, or stereo ( 2 channels unbalanced). 

A 1/4 unbalanced cable has only 1 wire and a ground, usually shielding the signal wire. The connector has 2 parts, the tip, and sleeve. The tip is the signal wire, and the sleeve is the ground.
A guitar cable is a common example of this type. For a guitar cable, it’s especially important at that the ground is wrapped around the signal wire and provides good shielding. This is because the guitar signal is high impedance, and is a very low level signal which receives a lot of amplification, this cable basically acts as a radio antenna, and so you want a cable that blocks this out as much as possible. A guitar cable longer than 20’ is generally not recommended.
If you need a longer run for a guitar, the common practice is to use a DI box, which converts the unbalanced high impedance guitar output to a low impedance balanced output which you can plug an xlr cable into and go to a preamp.