Examples of wiring options and audio flow in the studio.
- 1 Cable Types
- 2 Cable Organization
- 3 Color Coding
- 4 Break Out Panels and Sockets
Shielded Instrument Cable - Good choice
This is the classic type of cable used for professional audio wiring. It is also known as microphone cable, and balanced audio cable. It is typically terminated in XLR, TRS, or TS connectors. This cable can be used to carry unbalanced, or balanced audio and contains a shield braid to help keep out interference signals. Balanced audio is the standard for professional audio as it is much more resistant to outside interference. The connectors do need to be soldered onto the cable when not using premade cables. Use of 'no-solder' connectors is highly discouraged.
Network Cable - Highly recommended
Common computer network cable has excellent noise rejection and crosstalk resistance. It is designed to prevent signal problems up to much higher frequencies than audio signals. This cable is available in several configurations each capable of different amounts of signal integrity. The types which work well for audio signals are CAT5e, CAT6, CAT6a, and CAT7. In addition, shielded versions of the CAT5 and CAT6 cables are available, as well as CAT7 cable that always has a shield around each pair in addition to the shield for the entire cable.
CATx cables can be used on traditional TRS and XLR connectors, but perhaps where they shine is using RJ45 connectors. These are the connectors usually used on network cables and allow one to carry up to four audio channels on one cable the same diameter as traditional instrument cable! This provides the advantages of reduced number of cables, grouping of stereo channels, and easier tracing and routing of the cables. Another advantage of CATx cables is that they are available in many colors, allowing you to use different colors of cables for different audio signals. Adapters can be made or purchased to convert the RJ45 connector to and from XLR, TRS, TS, and RCA connectors.
Due to the low cost difference it is highly recommended to use shielded cables, and the individual shielding of CAT7 comes at a not unreasonable price. When making custom CATx cables or replacing the connectors, a crimping tool is required. The CAT7 is a bit more difficult to install ends on in the field due to all of the shielding, but for the tolerance of audio signals, it is still as easy as soldering on an XLR connector. If using shielded cable, including CAT7, be sure to use shielded RJ45 connectors so that the shield can do its job.
A commercial broadcast version of CATx cable used for audio, is known as StudioHub+. SH+ has quickly become a standard in recent years and many studio consoles and other equipment are now available with RJ45 connectors built in, thus eliminating the need for adapters. The SH+ standard only carries two channels per cable but adds the option for carrying DC power and ground in the other two pairs. This lets you power microphone and headphone amplifiers as well as carry the audio signal all on just one cable.
Due to the excellent resistance to signal interference, long cable runs of several hundred feet are capable given proper input voltages.
Consumer Analog Cables
There is one standard for consumer digital audio interconnects, S/PDIF. This signal can be carried electrically by a cable with RCA connectors, or optically using a Toslink cable.
The most common professional digital audio standard is AES. This signal is usually transfered through standard instrument cable with XLR connectors. Although 'special' cables are sold, they provide no advantage in most cases. Unlike analog audio which can be degraded by poor cables and connections, for the most part digital either works or doesn't so cable/connector issues are easily apparent.
The above two digital audio standards were developed somewhat in concert with each other. They are mostly protocol compatible but only compatible at the voltage level in one direction.
- An S/PDIF coaxial source can be fed to an AES receiver provided that the cable length is not excessively long, thus producing too much voltage drop. This length varies with cable type, and hardware of sender and receiver. A simple RCA to XLR cable will usually work to accomplish this setup.
- An AES source can not be fed to an S/PDIF receiver without damage unless the voltage levels are decreased and dynamic voltage range is compressed. There are commercial adapters to do this.
- Aside from the voltage issues, there is extra header information in the frames of an AES signal compared to S/PDIF and not all S/PDIF equipment will be accepting of this and it 'can' cause errors. The more expensive commercial adapters also take care of this issue as well.
If you think that things are bad behind your TV and/or stereo receiver at home, you "ain't seen nothing yet!" The number of connections between equipment for audio, power, network, and control circuits can be overwhelming. If you don't have a plan and try to keep things in order from the beginning it can quickly become a mess that no one can make sense of. The last thing you want to have happen is dealing with an on-air problem and trying to sort through a bunch of "snakes in a basket."
When possible avoid running power cords and phone lines parallel to audio cables. This is most important for unbalanced and/or unshielded audio cables.
Troughs and Hangers
Here is a suggested color code to use for your audio connections. Color coding greatly simplifies initial hook-up and eventual troubleshooting. It is suggested that the same colors be used for labeling the front of equipment and the channels on the studio console. If using network cables (CAT7) for your audio, it is also recommended to use colors that are not also used for your IT network. Colored heat shrink tubing or tyvek wire markers can be used to color code your cables. If using CATx cable, you can order patch cables in the base(first) color and then apply a marker in the tracer(second) color. Colored instrument cable is more difficult to find and can be expensive. If using instrument cable, you will likely have to apply markers for both colors and a third marker on stereo inputs and outputs, L, R, White, or Red, to signify which channel the cable is for. Only NEMA standard colors are used in the below scheme so cables and markers in these colors should be readily available.
|Green/Red||Telephone (caller in)|
|Green/Yellow||Telephone (Studio out)|
|Black/Red||Program(main) Audio Bus|
|Black/Yellow||Audition Audio Bus|