Introduction

This is a primer for using audio cables, how they work, and what the common cable types are. Below are a couple of books that are excellent reference materials that expand on the subject:

Wire, Cable, and Fiber Optics for Video & Audio Engineers by Stephen H. Lampen (Aug 1, 1997) http://www.amazon.com/Cable-Fiber-Optics-Video-Engineers/dp/0070381348/ref=lp_B001HO3HHQ_1_2?ie=UTF8&qid=1335303440&sr=1-2

Audio/Video Cable Installer's Pocket Guide (Pocket Reference) by Stephen H. Lampen (Jan 15, 2002) http://www.amazon.com/Audio-Video-Installers-Pocket-Reference/dp/0071386211/ref=sr_1_fkmr1_2?s=books&ie=UTF8&qid=1335303294&sr=1-2-fkmr1

How an Audio Cable Works

Audio cables work by sending electrical signals from one place to another. This is very similar to the way that electrical current flows from a power outlet in your house. However audio cables use much smaller voltages than a common 110 volt plug.

Electricity 101

In order for electricity to “flow” between two points you need two things: a “hot” or positive wire and a “neutral” or negative wire. This completes a “circuit” and allows the electrical signal from your instrument to your amp, mixing console or computer interface.

All standard audio cables use this basic electrical principle no matter what connector is attached to the end. This is what is happening when you plug your guitar into your amp with a ¼” guitar cable or when you connect your DVD player to your TV with an RCA plug, they both work exactly the same way.

Balanced and Unbalanced Audio Cables
I have noticed online that there seems to be a lot of confusion and long explanations about the difference between balanced and unbalanced audio cables.  All most guitarists and recording enthusiasts need to know is the basic electrical difference between the two and what that means for them.  I’m going to try to explain the difference in plain English as best I can.

Unbalanced cables work exactly as I just described. In a guitar cable for instance there is positive wire or “tip” which connects to the tip of the connector at the end of the cable. And a neutral “sleeve” that wraps around the wire connected to the tip. The neutral or sleeve serves two purposes: To provide a neutral conductor so that electricity can flow and to shield the positive middle wire from outside interference.

-Low impedance audio, or mic level would be 48-52 Ohms (3-pin XLR connectors, balanced lines).

-Higher (but not high) impedance audio for mixers and other distributive audio equipment instrument level is around 1,000 [between 680 to 1,800] Ohms (1/4" phone connectors, TS-unbalanced and TRS-balance lines).

-High impedance audio Mixers, other circuit applications, distribution amps and other distributive audio line level require 1,000 to 10,000 Ohms (RCA connectors, unbalanced lines).

Q: So my guitar cables and pedals are unbalanced? 
A: YES, nearly all guitar equipment is.

Q: Is that bad?
A: Absolutely NOT.

Unbalanced cables can be prone to outside electrical interference over long distances. Basically the longer the cable, the less effective the sleeve is going to be at shielding the cable from outside electrical interference. Fortunately most guitar cables and patch cables are relatively short so this is usually not an issue for most musicians. A good rule of thumb for any unbalanced cable is if it’s over 10ft long and you are using it in a room or on a stage with a lot of other electrical equipment you could hear unwanted hum, buzz, or noise.

Q: What does this mean for me?
A.(1) Nobody likes to be “tied” to their amp but try to keep guitar and other unbalanced cables around 10ft or shorter for the least amount of noise and strongest signal. (15ft is usually ok, 25ft is pushing it.)
A.(2) In recording situations it’s ok to use unbalanced cables in most cases but if you want crystal clear audio try to keep them under 10ft. Also, watch out for unbalanced connections on the back of rack gear. Having an unbalanced connection near that much other gear could cause noise problems.

Balanced Cables
Balanced cables still rely on a “hot” conductor and a “neutral” conductor to carry electrical signals but they add another element to the equation: a ground.    A ground is called a ground because well… it literally goes into the ground! Straight through the cable, through your balanced audio gear, through the wall to the fuse box and down a wire or pipe into the Earth. In balanced audio cables the sleeve is used as the ground. The ground or sleeve does NOT carry a signal and is NOT heard in the audio. It’s simply there to protect from unwanted noise while the hot and neutral carry the signal.

Now for the magic: the hot and neutral both carry the same signal, noise and all. Hot is flowing in a positive direction, neutral in a negative direction. Balanced audio equipment simply outputs the voltage difference between the two wires. Since the noise is represented equally on both hot and neutral it is “inverted” and cancelled out. I know this might sound complicated but what it means for you is that you can have hundreds of feet of  balanced cable and still have noise free audio.

Q. What types of things use balanced audio cables?
A. Microphones and recording equipment is, or should be, balanced in most cases.

Q. If I use a balanced cable with my guitar can I balance the signal?
A. No. The equipment you are using must have balanced connections as well.

Q. Why are balanced cables so expensive?
A. They are made with a process called “twisted pairing” which is more expensive to manufacture than unbalanced cables.

Q. If I have the choice of using balanced or unbalanced cables which one should I use?

A. In most cases if you are using balanced equipment you should use balanced cables. But if you get into a tight spot and need run something

unbalanced it’s ok as long as the cable length is short and you get no unwanted noise.

How to tell the difference between balanced and unbalanced cables:

• The technical name for guitar cables is TS which stands for Tip (hot), Sleeve (Neutral).
• Studio ¼” cables are called TRS which stands for Tip (Hot) Ring (Neutral) Sleeve (Ground)
• TS Cables have one ring on the connector:    
• TRS Cables have two. 
• Any cable that has three prongs or “legs” like an XLR Cable is usually balanced.  
• Some cables are made for odd routing situations and are three “legged” on one side and two pronged on the other. These are still unbalanced. 

Glossary of Cables:

Unbalanced:

TS 1/4":

This is the standard ¼” cable seen on guitars and unbalanced recording equipment.

TS 1/8” Mini:

A TS or “mono” mini plug is most commonly seen as an adapter.

RCA or Phono:

RCA connections are seen primarily on entry level recording equipment. They are also found on consumer products like DVD players, turntables, and older television sets.

Banana Plug:

Banana plugs are mostly used for consumer audio speaker connections.

Insert or Y Cable:

An insert cable splits a stereo signal into two mono parts and is referred to as a Y-Cable because it is literally shaped like a Y.

Balanced:

XLR:

XLR is the most common connection for microphones and is often referred to as a “mic cable”.

TRS ¼”:

(Notice the two rings around the top of the connector.)

TRS is a balanced ¼” cable that is used in studios and live sound reinforcement to minimize noise over long distances.

TRS 1/8” Mini:

The 1/8” “mini plug” connector is often used on headphones and other consumer sources like sound cards.

Tiny Telephone or TT:

The TT or Tiny Telephone is a balanced connection used for connections in professional patch bays.

Digital Connections:
Most digital connections use the same principals we have already discussed; they just use them in a different way. Digital cables are made to send “pulses” of current or light that can be decoded by a computer.  It is VERY important to use the proper cable type with digital connections.  Things like “impedance” or the amount of resistance present in the cable play an important role in how this information is sent. Just because a S/PDIF cable looks like an RCA Cable doesn’t mean the RCA cable plugged into your DVD player can handle a S/PDIF connection. You might experience strange errors and digital distortion if you use a cable that is not properly rated.

S/PDIF:

S/PDIF or Sony/Phillips Digital Interface is by far the most common digital connection. It uses a 75 ohm unbalanced RCA phono connection. You can use standard RCA cables if they are rated at 75ohms.

Optical or Light Pipe:

Optical or Light Pipe is a discrete multichannel digital standard developed for the ADAT. It is most commonly seen on digital audio interfaces and preamps.  You may also see optical ports on high end consumer devices as an audio connection. Optical cables use pulses of light to send information. They tend to be expensive and fragile so handle with care.

AES/EBU:

AES/EBU: is basically S/PDIF’s big brother. AES uses the same protocol as S/PDIF but it can handle more information at once. AES/EBU uses a balanced connection with XLR on both sides. When using an XLR make sure it is Type 1 (referring to pin order) and rated at 110 ohms.

BNC or Bayonet:

BNC is an unbalanced connection that is used primarily in professional video as an alternative to RCA. On the audio side of things it is mainly used to carry word clock information. BNC comes in 50 and 75 Ohm varieties, most audio equipment uses 75 ohm.

Multi-pin Connectors

Multi-pin connectors are usually found on high end audio interfaces and consoles, they are used as a balanced multi channel connection that saves space on the back of a piece of gear. Each pin on the connector is a discrete channel that carries audio or digital information from one point to another.

Most guitarists and home recording enthusiasts won’t run into these connections too often because they are mainly used in recording or live sound equipment that is very expensive.

D-Sub/DB25:

D-Sub is a family of connectors used on computer devices and comes in multiple pin configurations. The most common D-Sub connection is the one found on the back of VGA computer monitors. It is not uncommon for companies to use D-Sub to carry audio on high end peripherals because the connectors are common and relatively inexpensive.

Elco/Edac:

Elco and Edac (which in many cases are interchangeable) are large multi pin connectors that can have as many 120 pins. They can be heavy and have an actuating screw that holds the male and female connectors in place.

TDIF:

A proprietary type of 25 pin D-Sub that was created by Tascam.  It is found on a wide variety of professional recording equipment as an alternative to the ADAT standard.