I thought I would write a few paragraphs on audio cable basics. It is sometimes a topic that is overlooked. Not all newbies just happen to know this stuff automatically. I’ll try to keep it simple. Hopefully it will help those non-engineer types who just want their stuff to work without tons of background buzzing going on. Enjoy!
There are three basic types of audio cables. Unbalanced, Balanced, and Shielded. Unbalanced is the original design and most basic of the three. Shielding and Balanced are both design modifications that followed later to help solve a common problem. When I get to those parts, I’ll describe the problem first so that the solutions make more sense.
What is Unbalanced?
Any audio cable with only two medal conductors inside. These are usually the cheapest and simplest to mass-produce. Popular connectors (or plugs) used on these cables are 1/8” TS, ¼” TS, and RCA. TS stands for “Tip and Sleeve.” It describes the part of the plug that gets inserted into the jack. It only needs two parts which can carry current because the cable only has two conductors inside. It is impossible to get a balanced signal from a two conductor cable, even if plugged into a balanced output source. Examples of Unbalanced cables would be Guitar cables, Instrument cables, Insert cables, and Speaker cables. Some low budget microphones still use unbalanced cables with ¼” connectors.
What does Shielded mean?
Anytime you run a length of wire which caries audio signal, it also wants to act as an antenna. Yes, just like on a radio. It naturally pickups radio signals from the air and carries them to the end of the wire, right where we don’t want it to be. In most cases we can hear the extra added signal in our audio equipment as buzzing. In severe cases we can actually hear the radio program content coming through the audio system. This unwanted noise is called Radio Frequency Interference or RFI. Audio cables can also pick up electromagnetic leakage from AC cables and other nearby equipment. This type of interference is referred to as EI, and also causes buzzing or hum.
The earliest defense against this annoyance was to shield the primary conductor by wrapping something medal around it so the RFI cannot get through. The ground conductor was turned into a flat braided element which was then wrapped completely around the primary conductor. It protected the center conductor by intercepting the offending interference and carrying it to an electrical ground. We call this type of design a “shielded cable” because the center conductor is “shielded” from the RFI. Shielding can also be done with a foil surround instead of braided. While foil works even better, it can however crack and break from constant flexing. One must be careful not to bend sharply or wrap foil shielded cables too tightly. Shielded cables work pretty good until you want to make long cable runs, say longer than 25 feet. Then RFI can begin to be heard again.
What is Balanced?
The balanced cable was actually developed by a Telephone company to make extremely long cable runs possible while still rejecting RFI. It just happens to be perfectly suited for use in pro audio systems too. In order to accomplish this feat a third conductor was added to the cable and the way that equipment reads the signal was also changed. Balanced cables now use two AC conductors and one ground. The Ground conductor still does the same as before. Audio signal is realized by voltage differences that occur between the two signal conductors instead of varying voltage in just one conductor. RFI is ignored because it enters both of the AC wires equally. Since the interference level is equal on each wire, there is no voltage difference to be measured from it, so it has no perceptible affect on the audio signal.
Balanced cables can be identified by observing three parts on the plug. XLR and ¼” TRS are most commonly used. TRS stands for “Tip, Ring, and Sleeve.” The Tip and the Ring carry the AC current while the sleeve serves as ground. The outputting audio gear must have balanced outputs for the balanced cables to work correctly. If it does not, a DI box can be inserted into the cable run. DI boxes are used to convert unbalanced signals to balanced. They also work in reverse to unbalance a signal.
By combining balanced cables with shielding you would get double the protection against RFI. Quality balanced cables can accomplish long cable runs of 100’s of feet without noticeable RFI noise. While working on recording projects, you may not need to accomplish very long cable runs. However, balanced patch cables are still the best way to ensure minimum interference and good clean signal flow between processing gear. Almost every experienced audio engineer will recommend balanced connections for all sound reinforcement or recording projects.
NOTE: While headphones use a TRS connector, this does not mean they are balanced. They are the exception to the rule. They make use of the cable conductors in a different way to accommodate duel channels.
There are three basic types of audio cables. Unbalanced, Balanced, and Shielded. Unbalanced is the original design and most basic of the three. Shielding and Balanced are both design modifications that followed later to help solve a common problem. When I get to those parts, I’ll describe the problem first so that the solutions make more sense.
What is Unbalanced?
Any audio cable with only two medal conductors inside. These are usually the cheapest and simplest to mass-produce. Popular connectors (or plugs) used on these cables are 1/8” TS, ¼” TS, and RCA. TS stands for “Tip and Sleeve.” It describes the part of the plug that gets inserted into the jack. It only needs two parts which can carry current because the cable only has two conductors inside. It is impossible to get a balanced signal from a two conductor cable, even if plugged into a balanced output source. Examples of Unbalanced cables would be Guitar cables, Instrument cables, Insert cables, and Speaker cables. Some low budget microphones still use unbalanced cables with ¼” connectors.
What does Shielded mean?
Anytime you run a length of wire which caries audio signal, it also wants to act as an antenna. Yes, just like on a radio. It naturally pickups radio signals from the air and carries them to the end of the wire, right where we don’t want it to be. In most cases we can hear the extra added signal in our audio equipment as buzzing. In severe cases we can actually hear the radio program content coming through the audio system. This unwanted noise is called Radio Frequency Interference or RFI. Audio cables can also pick up electromagnetic leakage from AC cables and other nearby equipment. This type of interference is referred to as EI, and also causes buzzing or hum.
The earliest defense against this annoyance was to shield the primary conductor by wrapping something medal around it so the RFI cannot get through. The ground conductor was turned into a flat braided element which was then wrapped completely around the primary conductor. It protected the center conductor by intercepting the offending interference and carrying it to an electrical ground. We call this type of design a “shielded cable” because the center conductor is “shielded” from the RFI. Shielding can also be done with a foil surround instead of braided. While foil works even better, it can however crack and break from constant flexing. One must be careful not to bend sharply or wrap foil shielded cables too tightly. Shielded cables work pretty good until you want to make long cable runs, say longer than 25 feet. Then RFI can begin to be heard again.
What is Balanced?
The balanced cable was actually developed by a Telephone company to make extremely long cable runs possible while still rejecting RFI. It just happens to be perfectly suited for use in pro audio systems too. In order to accomplish this feat a third conductor was added to the cable and the way that equipment reads the signal was also changed. Balanced cables now use two AC conductors and one ground. The Ground conductor still does the same as before. Audio signal is realized by voltage differences that occur between the two signal conductors instead of varying voltage in just one conductor. RFI is ignored because it enters both of the AC wires equally. Since the interference level is equal on each wire, there is no voltage difference to be measured from it, so it has no perceptible affect on the audio signal.
Balanced cables can be identified by observing three parts on the plug. XLR and ¼” TRS are most commonly used. TRS stands for “Tip, Ring, and Sleeve.” The Tip and the Ring carry the AC current while the sleeve serves as ground. The outputting audio gear must have balanced outputs for the balanced cables to work correctly. If it does not, a DI box can be inserted into the cable run. DI boxes are used to convert unbalanced signals to balanced. They also work in reverse to unbalance a signal.
By combining balanced cables with shielding you would get double the protection against RFI. Quality balanced cables can accomplish long cable runs of 100’s of feet without noticeable RFI noise. While working on recording projects, you may not need to accomplish very long cable runs. However, balanced patch cables are still the best way to ensure minimum interference and good clean signal flow between processing gear. Almost every experienced audio engineer will recommend balanced connections for all sound reinforcement or recording projects.
NOTE: While headphones use a TRS connector, this does not mean they are balanced. They are the exception to the rule. They make use of the cable conductors in a different way to accommodate duel channels.
