Red Dog Music | Oct 9, 2018 | 0
Audio cable and connector guide: a Red Dog Music FAQ
Take a look around the back of a range of audio gear and you’ll often see a potentially bewildering array of holes for plugging things in and for getting everything connected together. Not sure about what cables to use where or why? You’ll want a butcher’s at the Red Dog’s audio cable and connector guide!
Don’t know how best to set up your studio gear using the most appropriate connections? This is the guide for you! Jack, phono, TRS, RCA, TS, TOSLINK, S/PDIF, ADAT, optical, coaxial, AES/EBU, DB25, D-Sub, XLR-F, XLR-M, mono, stereo, balanced, unbalanced, BNC- some all, few or none of these terms may be familiar to you. So what are they, what do they do and why are they used? Read on…
Let’s break it on down. There are a couple of main types of signal you’ll be sending around your studio: digital audio and analogue audio. Now we’re not going to talk about audio over USB/Firewire/Thunderbolt here, so we can leave all of that computer audio for another day. For now, we’ll just stick to those types of signals that you could find in a studio that didn’t have a computer in it.
Analogue signals – like the sort that come out of your microphone, guitar or that might run between your insert point on your [analogue] mixing desk and a compressor – are, fundamentally, the ‘actual audio’ itself.
Digital signals – are created by analogue to digital converters and are mathematically ‘encoded’ representations of your audio signal. A digital audio signal is just ‘information’ that can be used to recreate the analogue waveform later, but you couldn’t directly ‘listen’ to it.
Balanced and unbalanced, mono and stereo
If you look the connector on the end of your headphone cable, you’ll see that it has two circles of plastic, but the end of your guitar cable only has one. On your guitar cable, the metal contact points on the cable are called the tip and the sleeve. On your headphone cable, the extra bit of insulation creates another separate contact point, so you have the tip, the ring and the sleeve.
Cables with a tip and ring are called ‘TS’ cables, and those with the ring are, for obvious reasons, called ‘TRS’ cables. A TS cable can carry one analogue audio signal in an unbalanced form (more on that later…), a TRS cable can carry either two analogue signals (unbalanced), such as the left and right audio [stereo] signals for your headphones, or a mono signal in a balanced configuration.
Okay, now for the next bit: balanced and unbalanced signal. We’ve already said how a single mono analogue audio signal can be sent down a TS cable as unbalanced audio, or a TRS cable as balanced audio. What do these terms mean and what is the point of them?
It really just comes down to noise. Sending audio in a balanced configuration makes for fewew problems with interference due to the way that the signal and the cable are configured. If you want to know more, the Wikipedia page on balanced audio explains things really quite well. It’s not just TRS connections that are used for balanced audio, XLR connections – with their three pins – are also used to carry balanced signals.
So why aren’t all audio connections balanced? Expense is a major part of it: balancing and unbalancing those signals takes more components. Also, as there are more components involved, often including transformers depending on the circuit design, there can be changes to the sound, which may not be what the designers are after.
Right, with all that said, let’s crack on with the actual audio cable and connector guide!
Audio connector guide…
Jack connections or Phone connections come in TS (unbalanced mono) and TRS (balanced mono or unbalanced stereo) versions and in 1/4″ (6.3 mm) or 1/8″ (3.5 mm) sizes and are perhaps the most common format for analogue audio connection across the consumer and professional markets. From the outputs on your synth to the line-inputs on your interface and your headphones, chances are it’s a jack.
Again used for sending balanced mono analogue signals, XLR connectors come in two varieties: male (XLR-M) and female (XLR-F). Which is which should be self-evident… Continuing that analogy, on the back of your gear, the input connections will be on female sockets, ready to receive a signal from the male end of a cable. The XLR format is also used for sending digital signals generally using the AES/EBU protocol, but more on that later…
The standard for sending unbalanced signals, particularly in the consumer and hi-fi worlds, the RCA phono cable generally comes in pairs for sending stereo signals. This format is also used for sending digital audio using the S/PDIF coaxial format, which you often see on the back of many audio interfaces. As a digital connection, a single RCA cable can carry two audio signals – perfect for stereo – as the cable isn’t carrying the audio, but all those 1s and 0s that represent the signal.
The TOShiba LINK cable is used for sending digital audio down a fibre-optic cable. This type of connector can be used for both the S/PDIF stereo protocol, as well as the ADAT protocol for sending or receiving 8 channels of digital audio. The most common type of connector you will see is the more ‘square’-like connector, but a smaller format that fits into a 3.5 mm jack socket is also often used in a few devices such as some laptops.
You may be more familiar with D-Subminiature connections from the back of your old computer. Named for the ‘D’ shape of the connector, there are a range of sizes with a different number of pins that are used for different applications. The standard D-Sub connector in the big wide world of audio connection is the DB25 connector wired using the TASCAM pin-out standard. This standard can be used to carry 8 mono channels of balanced analogue audio.
DB25 cables are also used for the TDIF (Tascam Digital InterFace) digital audio standard. In this configuration, each cable can carry 8 channels of audio, but unlike ADAT, the TDIF standard is bidirectional, so one cable can carry 8 channels of audio in each direction.
Another coaxial cable format, BNC cables are often used for composite video signals. In the studio, they are generally used for sending wordclock signals for clocking your digital audio, but that’s for another day…
Audio cable types
Now that we’ve covered the connectors, that’s the hard part done. The simple bit is now just taking those connectors and choosing which need to be at either end of a cable to make everything work. Although there could be slightly more to it than that…
You will be able to easily find cables for the most common audio-carrying tasks quite easily 1/4″ jack to XLR or phono, XLR-F to XLR-M etc. And for hooking up your Universal Apollo 16 to your gear, DB25 to XLR and DB25 to 1/4″ jack are easy to find.
There are some things to watch out for though. While you could use an RCA cable to connect the output of your CD player to the S/PDIF input of your audio interface, but you won’t hear anything. There are also some specification differences in the RCA phono cables used for digital and analogue signals, with the cables for digital signals requiring a specific impedance to maintain their quality.
The same is true for XLR cables used for AES/EBU signals. As a general rule of thumb, the cables that are specified for digital signal use are fine to use for analogue signals, but not the other way around…
If you can’t find the cable you need, chances are you can get something that works using an off-the-shelf cable combined with an adapter or two. Of course, if you’re handy with a soldering iron – and confident in your ability to solder the right thing to the right thing on the other end! – then making your own cables can work out a lot more cost effective in the long run.
Y cables, splitter cables and insert cables
Beyond just cables that just run from A to B, there are some more complicated cable types which can be very handy in a studio context.
The first of these is the insert cable. Generally featuring a 1/4″ TRS jack at one end, then forming a ‘Y’ shape to split into two 1/4″ TS jacks at the other, the insert cable is designed to carry an unbalanced signal from an unbalanced insert point on your mixing desk, to a piece of outboard, and then take the processed signal back again.
The way these are configured should be marked on the insert point on the desk and on the TS ends of the cable, using terms such as ‘tip send’ and ‘ring return’, with the TS ends of the cables labelled tip – to plug into the input of your gear- and ring – to plug into the output.
For other situations, you may want Y cables to act as splitters to send a signal to more than one place, although, as this will change the impedance that is being seen, the audio can sometimes be compromised, so it can be worth investing in dedicated splitter units.
Good cabling practice
How you go about wiring everything up in your studio can have a big bearing on the quality of your audio. There is often a lot of hyperbole surrounding cables (particularly in hi-fi circles), so you don’t necessarily need to spend a fortune on boutique, esoteric cables. However, keeping your cables neat, and keeping audio cables as far away from power cables as you can be make a big difference.
If audio cables and power cables do have to cross, try and do it at 90 degrees and avoid having them run parallel if at all possible. Some velcro cable ties can be very handy things to have around, too.
For some situations, cable looms can be very practical and also work out more affordable than individual cables.
Also, neater cabling makes it much easier when you need to make some gear tweaks!
Hopefully that should cover most things, we’ll save speaker cables and speakon connectors for another day!
Red Dog Music is the UK’s friendliest musical instrument and pro-audio dealer. Between our 5000 square foot Edinburgh shop filled with an incredible range of products, and a London showroom in Clapham specialising in high-end instruments, dj and pro-audio, Red Dog Music has you covered from north to south and from performance to playback.