If you look at the back of an audio interface, you see round XLR-style sockets and slim, rod-like sockets side by side. Cables look alike too, and they are one of those pieces of gear that make it easy to wonder which one to use. This article sorts out, based on official materials from Focusrite (an audio interface maker) and Neutrik (a connector maker), the differences among the three cable types XLR, TRS and TS, and how to connect microphones, guitars, studio monitors and headphones.
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Bottom line: choose by balanced or unbalanced
- It is easier to sort cables by thinking of two kinds: “balanced connections” and “unbalanced connections”.
- Focusrite explains that balanced cables can use a TRS (tip-ring-sleeve) connector or a 3-pin XLR connector.
- Unbalanced cables mainly use a TS (tip-sleeve) connector, and are generally used for instruments such as guitars.
- The basic pairings are XLR for microphones, TS for guitars, and TRS (or XLR) for studio monitors. However, the sockets differ from device to device, so always check the socket labels on the device and its manual.
The difference between balanced and unbalanced connections
Unbalanced connections
Focusrite explains that an unbalanced cable has only one wire carrying the signal and has no mechanism to cancel noise (interference). The ground (the reference wire) is used as a “shield” wrapped around the signal wire. These are mainly used as cables for instruments such as guitars, and the connector is TS or RCA (such as red and white plugs).
Balanced connections
In a balanced connection, another conductor is added to the cable. Focusrite explains that a balanced cable is far better at canceling the effects of noise than an unbalanced one. It is considered useful when running long cables or when noise is a concern. Neutrik also explains that for long distances and noise-sensitive uses, it is customary to use 3-pole connectors and balanced cables.
“Balanced” does not mean the signal is two channels, left and right; it is a method of carrying one sound (mono) over two wires. Neutrik also writes that even a balanced connection using a 3-pole connector keeps the signal mono.
What gear is balanced
Focusrite lists the following as gear that often has balanced inputs and outputs.
- Studio monitors (monitor speakers)
- Synthesizers, electric pianos and keyboards
- Rack effects and microphone preamps
- Mixing consoles
Focusrite also explains that all of its 6.35 mm (1/4 inch) jack inputs and outputs are “mono balanced” (this is about Focusrite’s products).
The differences among the three connectors
XLR: the standard connection for microphones
XLR is a round connector with three pins. Focusrite explains that XLR is used for the signal a microphone outputs (mic level). On Focusrite products, all mic-level connections are XLR. Even on a combo jack (a socket that accepts both XLR and a 6.35 mm jack), the XLR part is for microphones only. The difference from USB microphones is explained in “USB microphones vs XLR microphones with an interface“.
TS: a 2-pole, unbalanced connector
TS stands for “tip and sleeve”, and it has two conductors (it is also called 2-pole). One is the audio signal and the other is the ground. Focusrite explains that TS cables are used mainly for unbalanced mono signals such as guitars, in the 6.35 mm size. The “instrument level” signal that instruments such as guitars and basses output is in most cases unbalanced, and is connected through a TS jack.
TRS: a 3-pole connector, balanced mono or unbalanced stereo
TRS stands for “tip, ring, sleeve”, and it has three conductors (3-pole). Two carry audio signal and one is the ground. Focusrite explains that TRS has two ways of being used.
- Balanced mono: The line inputs and outputs of many Focusrite products work this way.
- Unbalanced stereo: Headphone outputs work this way. The left and right sounds are carried on the tip and the ring.
Note that even if they look the same as TRS, there are two ways the contents are used.
Connecting each type of gear
| What you connect | Basic cable | Point |
|---|---|---|
| Microphone (condenser or dynamic) | XLR | Mic level is connected with XLR |
| Electric guitar or bass | TS (6.35 mm) | Instrument level is basically unbalanced. Avoid TRS for a guitar |
| Studio monitors | TRS or XLR (balanced) | Match the input socket on the speaker |
| Synth or electric piano | TRS or TS | Check in the manual whether the output socket is balanced |
| Headphones | TRS (unbalanced stereo) | You may need a 3.5 mm to 6.35 mm adapter plug |
Microphones
A microphone connects to the audio interface’s microphone input with an XLR cable. A mic-level signal is very small and has to be amplified by a preamp. It is fine to think of the cable as running straight XLR from the microphone to the interface.
Guitars and basses
Guitars and basses connect with a TS cable to an input that accepts instrument level. Focusrite advises checking, by a label or a button, whether the input socket supports instrument level, and, if it is a socket shared with line input, switching it to instrument input. This is because, if left on line input, the input impedance (how hard it is for electricity to flow) does not suit the instrument.
Studio monitors
Focusrite explains that for speakers with balanced inputs, using a balanced cable to connect to the interface’s balanced outputs makes it easier to keep noise from getting in. If the speaker has only unbalanced inputs, use an unbalanced cable.
How to choose speakers is explained in “How to choose studio monitors“.
Headphones
For headphones, a 3.5 mm TRS is standard, and if the interface’s headphone output is 6.35 mm, you need an adapter plug. Focusrite explains that a 4-pole (TRRS) plug, such as on a gaming headset with a microphone, cannot be connected directly to an interface’s headphone output.
Common mistakes
1. Plugging TS into a TRS input makes it unbalanced
Focusrite explains that you can plug a TS cable into a TRS input or output, but the signal becomes unbalanced, the signal drops by 6 dB, and it becomes more susceptible to noise. Neutrik also explains that connecting a 2-pole plug to a balanced line halves the signal voltage. You will still get sound, but it may be quieter or noisier.
2. Using TS on a stereo input or output loses one side
TS cannot carry a stereo signal. Focusrite explains that connecting TS to a stereo TRS input or output loses one of the two channels.
3. Balanced TRS and stereo TRS are different things
Even though both are TRS, balanced mono and unbalanced stereo (such as headphones) are not meant to be connected directly to each other. Focusrite explains that doing so loses one channel and can cause sound quality problems.
4. Do not use TRS for a guitar
Focusrite advises avoiding TRS for most guitars. This is because problems can occur with gear such as effects pedals that assume a TS connection.
5. Do not connect speaker-level output to a line input
The speaker output of a power amplifier or a guitar amp has a high voltage, and connecting it to a mic, line or instrument input can damage the input (Focusrite’s explanation). Just because a cable fits does not mean it is okay to connect.
6. The XLR side of a combo jack is for microphones only
On Focusrite products, the XLR part of a combo jack is dedicated to mic level. Plug line-level gear into the 6.35 mm hole in the center.
Frequently asked questions
Q. Can I convert between XLR and TRS?
Focusrite also introduces a cable from a “TRS jack to a 3-pin male XLR” as a cable for balanced connections. What matters is choosing a cable that matches the socket on the device. However, check separately whether the signal levels of the gear you connect match (mic or line).
Q. Is it not okay to use an unbalanced cable?
You can use one. Focusrite advises using an unbalanced cable for gear with no balanced inputs or outputs (for example, speakers with only unbalanced inputs). For things like a guitar, whose signal is unbalanced to begin with, TS is the standard.
Q. Can I tell TS and TRS apart by looking?
You can tell by the number of black insulating bands (rings) near the tip of the plug. TS has one band and TRS has two (Focusrite’s explanation).
Q. Is balanced better for long cables?
Neutrik explains that for long cables and noise-sensitive uses it is customary to use balanced cables. Conversely, it writes that for short connections such as a guitar, a 2-pole unbalanced one is enough.
Summary
Choose a cable by “balanced or unbalanced” and by the socket on the device. The basics are XLR for microphones, TS for guitars, and balanced TRS or XLR for studio monitors. Common mistakes are that plugging TS into a TRS input still makes sound but leaves the signal unbalanced, and the difference between stereo and balanced TRS. If you are unsure, check the socket labels on the gear and the instruction manual.
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