What Audio Cable Do I Need for a PA System?

Delving Deeper: Analogue Audio Signal Cables

When it comes to setting up a PA system, understanding the different types of audio cables and their specific uses is essential. Let’s dive a bit deeper into the world of audio signal cables, exploring more types, answering some common questions, and providing you with a comprehensive guide to ensure you choose the right signal cables for your needs.

Audio Conversion Cables

Audio signal cables are available with mismatched connectors to suit different equipment, and these are known as conversion cables.

A classic example of this is the 3.5mm mini jack to stereo RCA cable, which allows you to connect the output of mobile phones and laptops into an amplifier or mixers RCA line input.

You can convert pretty much any line-level audio connector to a different type, be it RCA to jack, or XLR to single or double jack, and any of these configurations are perfectly fine.

The only thing to consider is a balanced signal requires either an XLR or TRS at either end to retain its configuration (balanced needs 3 contacts). If you take an XLR and convert it to stereo RCA plugs for example, you will have made it an unbalanced cable. It will still work just fine, just that you won't benefit from the noise reduction.

Signal Cables vs Speaker Cables

Signal cables and speaker cables serve different purposes and are designed differently to handle their specific roles. Signal cables, such as RCA, XLR, and Jack cables, are used to transmit low-level audio signals from one piece of equipment to another. These cables are typically shielded to protect the signal from electromagnetic interference and noise. They can be wired for a balanced or unbalanced signal.

This may sound rather obvious when considering the purchase of audio equipment, but the desired performance level, be it sound quality, detail, volume level, bass response, or all of those together, is as important to consider in a living room as it is in a large nightclub.

Speaker cables, on the other hand, are used to connect amplifiers to speakers. They carry high-power audio signals and need to be thicker to handle the higher current. Speaker cables are usually unshielded because the signal they carry is less susceptible to noise. You would only use speaker cable with passive speakers and an amplifier, and passive speakers won't have RCA or XLR sockets, helping avoid any wrong usage of those cables.

Jack plugs however can be a problem to the uninformed, as there are professional speaker cables that use the same ¼” (6.35mm) jack connections as those found on musical instrument signal cables. They each use a very different internal cable structure though, and neither is suitable for the other's task, with the risk of serious damage if an instrument lead is used to power a speaker.

Using the wrong type of cable for a specific purpose will result in poor sound quality and often damage to your equipment, so always ensure you have the correct ones. We have a guide called 'What Speaker Cables Do PA Speakers Use?' to all your speaker cable questions in better detail.

Balanced vs Unbalanced Cables

A standard analogue audio signal will either be in a stereo format ( from a Mixer, CD Player, Record Player) or will be mono (Musical Instruments, Microphones). These signals will usually be output from the source device as ‘unbalanced’ (hot signal and a ground connection), or as a ‘balanced’ signal (positive and negative hot signals and a ground).

Balanced cables, like XLR and TRS cables, are designed to reduce noise and interference. They achieve this by using three conductors: a positive signal, a negative (inverted) signal, and a ground. The positive and negative signals are out of phase with each other (in fact they are a mirrored image), and any noise picked up along the cable is cancelled out when the signals are recombined at the destination.

Unbalanced cables, such as RCA and TS cables, use only two conductors: a signal and a ground. They are more prone to noise and interference, especially over long distances. For short runs, unbalanced cables can work just fine, but for longer distances, balanced cables are the better choice.

Does Balanced sound better than Unbalanced?

In general, balanced cables provide better sound quality than unbalanced cables because they are less susceptible to noise and interference. This is especially true over long distances. However, for short runs, the difference in sound quality may be negligible.

Due to the nature of how the signal is split for a balanced signal, it retains more detail, especially on the top end, though the main reason to favour XLR is its noise rejection, which is handy in electrically noisy areas such as recording studios, or of course, live stages where long cables are prone to stray EMI and RF interference.

It also depends on the equipment the cable is connecting. For a microphone say, which is a highly sensitive pickup, the audible difference can be quite noticeable from a balanced to unbalanced cable, and you will find all professional mics will use XLR for this reason. For the line signal between a mixer and an active speaker though, the benefits are less noticeable unless you’re using extra-long cable runs, so it's more about personal preference.

The choice between balanced and unbalanced cables should be based on the specific needs of your PA system and the environment in which it will be used.

Cable Length Considerations

The length of your audio cables can significantly impact sound quality. Let’s look at some specific cable types and their optimal lengths:

• RCA Cables

  RCA cables are best kept as short as possible, ideally under 6 meters (20 feet). Beyond this length, the unbalanced nature of RCA cables makes them more susceptible to noise and signal degradation.

• Jack Cables

  The length of jack cables depends on whether they are balanced (TRS) or unbalanced (TS). Unbalanced TS cables should generally be kept under 7.5 meters (25 feet) to avoid noise issues, while balanced TRS cables can be run for longer distances, similar to XLR cables.

• XLR Cables

  XLR cables can be run for much longer distances, often up to 100 meters (328 feet) or more, without significant signal loss or noise interference. This makes them ideal for large venues and long cable runs.

Stereo or Mono?

Source devices for playing pre-recorded music such as a media player, CD player, laptop audio, record player etc, will be sending out a stereo signal, whereas microphones and musical instruments are mono. Stereo requires a plug or plugs to have two contacts and grounding connection for its split left and right audio channels, while mono only requires a single contact and ground.

Most professional or commercial audio applications (a nightclub for example) will be mono. This is because the listener is not in a fixed position, and mono allows you to hear the full music signal wether you are standing still or moving. Stereo, on the other hand, was designed as a spatial effect to enhance the soundstage and ‘immersion’ for Hi-Fi and personal audio. Its split left and right channels require the listener to be in a central position, which simply isn't possible in a venue, as at some point people will be only hearing a left or right channel as they move out of the ‘sweet spot’. This will introduce an odd, out-of-phase experience that’s missing chunks of the audio.

On a smaller level, for a live band or mobile DJ, the reasoning is the same, as your audience is a movable factor.

The old adage is ‘play out in mono, play in in stereo’ and this serves well in most situations.

Other Common Audio Cable Types

In addition to RCA, jack, and XLR cables, there are several other types of audio cables you might encounter when connecting your equipment:

• MIDI Cables

  MIDI cables are used to connect some electronic musical instruments and other MIDI-compatible devices such as high-end DJ controllers. They transmit digital data rather than audio signals, allowing devices to communicate and control each other.

• Optical Cables

  Also known as TOSLINK, optical cables transmit digital audio signals using light. They are commonly used in home theatre systems and some professional audio setups. Optical cables are immune to electromagnetic interference, making them a good choice for environments with high levels of electrical noise, though they are limited in length due to signal degradation.

• Coaxial Cables

  Coaxial cables are also used for digital audio connections and can carry high-quality audio signals. They are less common in PA systems but can be found in some professional and consumer audio equipment. They are often used for connecting subwoofers to a home cinema amplifier.

Choosing the Right Cable for Your PA System

When selecting cables for your PA system, consider the following factors:

• Distance

  For long cable runs you should ideally choose balanced cables such as XLR or TRS to minimize noise and signal loss. As with any signal cable, the shorter you can make the run between equipment, the better it will perform.

• Equipment

  Ensure the cables you choose are compatible with your equipment’s input and output connectors. Avoid unnecessary conversions or adapters. For example, if your mixer has XLR and RCA outputs, but your active speakers only have RCA, then buy yourself a decent-quality RCA cable. Coming from an XLR to an RCA serves no purpose unless its the only option.

• Environment

  Consider the environment in which your PA system will be used. In areas with high levels of electrical interference, you really should opt for balanced cables if possible to ensure the best sound quality.

• Budget

  While high-quality cables can be more expensive, they often provide much better performance and durability, with better insulation and tougher materials for the cable and connectors. Invest in good-quality cables to avoid frequent replacements and ensure reliable performance.

Practical Tips for Cable Management

Proper cable management is crucial for maintaining a clean and organized setup. Here are some tips:

• Easy Identification

  Use labels or colour-coded tape to identify different cables easily. This will make it easier to troubleshoot issues and reconfigure your setup as needed. More expensive XLR plugs can have coloured identifier rings attached to them for convenience, or the physical cable can be coloured.

• Avoid Tangles

  Use cable ties or Velcro straps to keep cables neatly bundled. Avoid coiling cables too tightly, as this can damage them. No sailors knots! Audio cables need to be treated with respect if you want them to last.

• Keep Cables Off the Ground

  Where possible, use cable trays or hooks to keep cables off the ground. This reduces the risk of tripping hazards and protects the cables from damage. Sometimes this is unavoidable, but floor-draped cables ideally should be taped down or have something placed over them to avoid being crushed by foot traffic.

• Regular Maintenance

  Check your cables regularly for signs of wear and tear. Replace damaged cables promptly to avoid performance issues. If using a lot of cables such as in a live band setting, it’s worth investing in a cable tester, which is an electronic meter that will test the continuity and the connectors of a variety of signal cable types.

Summary

Choosing the right audio cables for your PA system is crucial for achieving optimal sound quality and performance. Whether you’re using RCA, Jack, or XLR cables, understanding their specific uses and limitations will help you make informed decisions.

Balanced cables are ideal for long runs and environments with high electrical interference, while unbalanced cables can work well for short distances and general audio connections. Remember to consider factors such as distance, equipment compatibility, and environment when selecting your cables. Proper cable management and maintenance will ensure your PA system remains reliable and easy to use. By following these guidelines, you can ensure that your PA system delivers the best possible sound, whether you’re performing live, recording in a studio, or simply enjoying music at home.