Audio/Video Cables & Connectors FAQ

Old 10-09-07, 06:23 AM
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Audio/Video Cables & Connectors FAQ

This post details the commonly used connectors and cables for video and audio. It is an update to the long-standing sticky originally posted in early 2004 by Stereoguy. Please PM me with comments and suggestions for updates.
-- Rick Johnston

A Brief Glossary, in no particular order:

Wire: A wire is a copper string, usually coated or covered with a PVC insulator. It can be one solid piece of copper, or it can have multiple strands inside the insulation. The wire thickness, called gauge, dictates its current-handling capacity. The smaller the gauge number, the thicker the wire. Cat 5 is 24 gauge. Household AC wiring to the receptacles is typically 12 gauge.

Cable: A cable contains one or more insulated wires, called conductors, inside the jacket. The term “cable” is also used generically to describe a distributed broadband television infrastructure. For our purposes, the term will apply to audio signal cables, video signal cables, and speaker cables.

Shield: A cable can also contain a “shield,” which is usually a foil wrap accompanied by either a bare drain wire or a braid. The shield is attached to ground and helps prevent unwanted electromagnetic and radio-frequency interference (EMI/RFI) from entering the signal conductors. Shielded cable is used for all low-level signal connections except telephone. High-level speaker cables are generally not shielded.

Plugs & Jacks: Plugs are the connectors that attach to cables. Jacks are mounted on devices. Jacks receive plugs. Almost everything is either color coded or the connectors are “keyed,” which means they will only go into jacks designed for that connector. A keyed connector (such as S-Video) will only go into the jack if it is properly aligned.

Input/Output (I/O): Outputs always connect to inputs and are usually labeled as such. Sometimes jacks are labeled “Play” (output) or “Record” (input).

HDCP: A scheme for content protection that forces devices to "handshake" and exchange encryption keys before they'll play full-resolution HD audio and video.

Maximum Cable Length: The distance at which a signal begins to degrade. Analog line-level A/V cables can be run at least 50 and up to 100 feet with no adverse effects. Digital line-level cables have finite maximums (see below). Depending on what it's used for, RG59 and RG6 can be run well over 100 feet. Speaker cables can also be run as long as necessary in the average home, but distance dictates the gauge of the wires.

Cabling Your Home:

Many homes are now being wired for more than just cable TV. Data, telephone, video, audio, cable modems, digital cable, satellite TV, and speakers are some of the cables that are commonly hidden behind the walls along with the AC wiring. Generally, all low-level signal cables can be run together with no adverse effects.

The exceptions are AC power and speaker wiring. When developing a wiring plan for your home, try to keep your signal cables a distance of at least one foot from AC and speaker wiring. A good rule of thumb is to run signal lines at least one wall stud away from AC or speaker lines. If you must cross over AC or speaker lines, do it at right angles. Also try to keep signal cables away from dimmers and fluorescent lighting ballasts.

Many homes are being “future-proofed” by installing flexible plastic conduit (called Smurf Tube because of its bright blue color). The smurf tube allows you to pull new lines at any time.

IMPORTANT! Use only cables that are rated for in-wall use! Non-rated cabling won’t be up to code and will cause you to fail your electrical inspection!

Digital audio uses the S/PDIF (pronounced “SPID-if”) protocol with several different connection options:

Optical Digital
Called a Toslink connector, this type of interconnect uses pulses of light to carry the audio signals to a maximum distance of 10 meters (32 feet).

Coaxial Digital
Usually an orange RCA connector. Although standard audio cables can be used, it is preferable to use a cable designed for digital audio.

BNC Digital
Pro systems use BNC connectors with heavily shielded 75-ohm coax cable (the same cable that’s used for CATV with different connectors). BNC-to-RCA adaptors at both ends allow this to be used on consumer Coaxial Digital ports and is the preferred method for long runs.

1/8” or 3.5mm Stereo Mini
Computer sound cards typically have S/PDIF ports that use this type of interconnect.

Color-coded white (left) and red (right), RCA connectors are the standard for analog consumer gear. Although both digital and analog I/Os use RCA connectors, they cannot be interconnected. In other words, don’t try to connect the orange output of your DVD to a red or white input on the receiver. You won’t do any damage; it just won’t work.

1/8” or 3.5mm Stereo Mini
Computer sound cards and portable devices use this connector. A cable may contain one 3.5mm mini connector at one end and two RCA connectors at the other to interface portable players with home stereos.

The most common connections are made via spring-loaded terminals or binding posts, usually color-coded red and black. It is important to maintain proper polarity to the speakers: Make sure you connect red to red and black to black on all of your speakers. It is also important to use thicker wiring for speakers than you would use for line-level signals. Typical speaker wire is at least 16 gauge, with 14 gauge being the preferred thickness, especially for runs over 25 feet. Virtually all unshielded cabling will work for speakers – even lamp cord. However, if you plan to run speaker cables inside your home’s walls, the cable must be rated for in-wall use.

Almost all of today’s Surround Sound Receivers have an RCA Subwoofer output. You can use any cable with RCA connectors to run from this jack to your subwoofer. If your receiver doesn’t have an RCA Sub Out, you can still use a subwoofer with your system. Choose a subwoofer that has speaker connections (sometimes called “High Level Inputs”). Connect the receiver’s speaker outputs to the speaker inputs of the sub, and connect the sub’s speaker outputs to your speakers.

The High Definition Multimedia Interface simplifies connections from digital cable boxes, satellite boxes, HD-DVD players, and video games to your HD TV. This all-in-one interconnect carries HD video, digital audio and format data on one cable, allowing your TV to automatically sense and adjust for the various hi-def formats. Cable quality will have an impact on length. All HDMI cables will hold spec at all resolutions for 15 feet. For runs up to 40 feet, only the higher quality cables will hold the spec (or will force you to view lower resolutions). Longer runs are possible, but require expensive extenders, amplifiers, repeaters, or conversion to fiber and back.

Until a few years ago, the Digital Visual Interface was the standard for HDTV connections. Today it is used primarily for computer-to-monitor and multimedia projector connections. Adaptor cables are available that allow you to use DVI outputs with HDMI inputs, however they may not provide for HDCP authorization (which means you may not be able to see your HD video in full resolution, if at all). The main drawback to DVI is the maximum cable length of just 15 feet. When adapted to HDMI it will take on the longer maximum cable length for HDMI, depending on the quality of the HDMI cable. Note that audio is not typically carried on DVI cables, although some manufacturers use it to do so. Most manufacturers also include analog RGB as part of the pinouts.

Serial Digital Interface, found primarily on pro-series gear, is a digital format that uses BNC cables. SDI carries video in all broadcast formats, plus digital audio and format data. SDI can be run 100 feet or more over copper RG6.

RGB(HV) Video
Used primarily for VGA monitors and multimedia projectors, RGBHV separates the video into the three primary colors – red, green and blue -- from which all other colors are derived. H (horizontal sync) and V (vertical sync) are signals that allow the monitor to sync to the source. RGBHV video connectors are typically 15-pin D-Subs, but some schemes use five individual cables for red, green, blue, H-sync and V-sync.

Component Video
Analog Component video jacks, color-coded red, green, and blue, are I/O’s that use RCA connectors. They separate the video signal into three components, but they are not the same as a VGA’s red, green, and blue. Analog component video has a luminance (black & white) channel and two “difference” channels that are used to derive the three primary colors of light. Although audio cables will work with these interconnects, it is best to use cabling that is designed for video signals. (Three yellow cables can be used, provided you connect them to the proper jacks at both ends.)

S-video, also called Y/C, separates the video signal into two components: black & white “luminance” and color “chrominance”. A special cable and connector with four pins is used for I/O. The connector is keyed so it can only be inserted one way. Usually there is an arrow or other mark at the top of the plug that allows you to line it up to the jack.

Composite Video
Composite Video carries all of the components of the signal on one RCA cable. Again, try not to use audio cables for this connection. It is color-coded yellow to indicate that it is a video connection.

RF, F, RG, or generic “Cable”
Commonly used to connect TVs and VCRs to antennas and distributed cable systems. It is also used between satellite dishes and receivers, for digital cable, for cable modems, and signal interconnects where heavy shielding is required. RG59 and RG6 are the two cable types found in the home, but as bandwidth climbs ever larger into the gigahertz range, RG59 is being phased out in favor of RG6’s superior electrical properties for high-frequency connections.

Both types can have different formulations inside the jacket that dictate its use. For broadband (multi-channel) applications including standard cable and satellite, a copper-clad steel center conductor protected by an aluminum foil shield is the best choice. For baseband (line-level) and digital signals, a pure copper center conductor and a 95% copper-braid shield is used.

Two types of connectors are found on the ends: “F” connectors are used for broadband applications. BNC connectors are used for baseband and digital signals. Both of these connectors are also commonly adapted to RCA to mate with consumer gear.

Photo Credits
Radio Shack
Denon USA
Creative (Soundblaster)

Thanks to Integrator97, HotinOKC, and GregH for their assistance.

Last edited by Rick Johnston; 10-15-07 at 04:30 AM. Reason: Update

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