For all of the high-tech digital audio devices out there, there is still a lot of analog equipment and an array of cables being used in church sound systems today.
Each cable typically comes with its own type of connector, but not all cables are this way. This is where things can get confusing for a new sound team volunteer. For Example:
• Microphone cables come with XLR connectors
• Stereo cables are typically RCA or 3.5mm jacks
• Modern speaker cables come with Speakon® twist-lock connectors
One Connector, Many Cables
There is one connector type that can be used for all of these cables. That connector is the ¼” “phone” plug. The venerable 1/4″ (6.35mm) phone plug has been with us for a long time – since 1878! Something that has been around that long is bound to have a lot of different uses associated with it. It’s called a “phone” plug because the original use was so that operators could manually patch telephone lines and connect calls at the central station.
Today this ¼” plug is mainly used for sound systems and it is used for five primary functions:
1. Stereo cables (headphones)
2. Unbalanced cables (guitars)
3. Balanced pro audio cables (console outputs)
4. Insert patch cables (external processors like reverb or compression)
5. Speaker cables (monitors & mains)
The first four cables may look exactly the same, but they have different uses for the signal conductors in the cable. The last one (speaker cables) can cause huge problems if you use the wrong cable in the wrong place! Even though the connector can be the same shape and size for each of the five applications, you need to pay special attention to the cable configuration and how it relates to your equipment.
How It Works
It may be helpful to see how this works with respect to the connector segments. There are two types of ¼” plugs that are commonly used in live sound: TS and TRS.
- TS stands for Tip Sleeve
- TRS stands for Tip Ring Sleeve
This image is an example of a typical guitar or instrument cable connector.
Unbalanced Mono instrument ¼” plug
There are only two connections, a “+” and a “- “or “shield.” These connections carry a low voltage mono audio signal from the instrument to the amplifier or direct box. This connection is “unbalanced” because the “-” and “shield” is the same conductor.
This next example is also an unbalanced connection, but it is a stereo cable with two + conductors, one for left and one for right.
Unbalanced Stereo ¼” plug
This type of connection is common for headphones and other stereo devices. It can also be used for non-stereo functions that require two channels in the same cable, like insert patch cables where there is a “+” for send, a “+” for return, and a “-” or “shield” as the common conductor.
This last image is an example of a “balanced” mono plug. This can be used to send audio signals longer distances than unbalanced cables, which are typically only good for about 20’. Notice how this connector is the same style of plug as the stereo plug, but it uses the segments differently.
Balanced Mono ¼” plug
This type of balanced cable can be used in similar fashion as a microphone cable, it just has a ¼” TRS plug on the end instead of a 3-pin XLR. The conductors still function the same – it just depends on what is plugged in on either end.
This could really be an exhaustive audio course topic all by itself, so we won’t get too complicated here.
The important thing is that you need to pay attention to what your audio OUTPUT jacks are configured to deliver, and then compare that to what your audio INPUT jacks are expecting to receive. Then use the right cable and connector type for the job.
If your gear sends out a left/right unbalanced stereo signal, don’t plug it into a piece of gear expecting a balanced mono input. You’ll lose half of your audio signal (the right channel most of the time), and you could cause some other system anomalies and noise.
If you’re unsure about the gear, jacks, and signal types you’re working with, read the manual or do a quick Google search on the type of connector and conductors used. You can generally find the details pretty quickly.
One more thing to be careful with:
DO NOT use an instrument cable as a speaker cable, or vice versa. Even though the ¼” TS plug type might be the same, the cables are definitely not the same.
- A speaker cable does not use a shield wire like an instrument cable does.
- Using the wrong cable or connector for the wrong purpose can compromise the audio signal or it could even damage the cable or equipment.
Hopefully, the images and descriptions help clear up a little confusion.
OPTIONAL REFERENCE NOTE
(For more info on the history of the phone plug, check out this Wikipedia entry.)