Connecting a guitar, bass guitar, synthesizer, keyboard (and many other instruments) to their respective amplifier is often as easy as plugging one end of a patch cable into the instrument and the other end into the amp. If you’ve ever wondered how this simple set up works on a more technical level, this article is for you!
How do patch cables carry audio? Patch cables, AKA patch cords or 1/4″ (6.35mm) TS (tip-sleeve) cables, are unbalanced cables that carry unbalanced audio signals from one male end to the other male end. There are two conductors in the cable: one carries the signal and the other acts as a shield and return path for the signal.
In this article, we’ll discuss patch cables in greater detail; how they carry audio from our instruments, and how to get the best results out of our patch cables.
Table Of Contents
- What Is A Patch Cable?
- Unbalanced Audio Vs. Balanced Audio
- The Outputs Of Various Instruments
- The Inputs Of Headphones And Loudspeakers
- The Inputs And Outputs Of Other Audio Devices
- Patch Cables For Guitar And Bass
- Patch Cables For Keyboards-And-Synthesizers
- Patch Cables For Microphones
- Patch Cables For Headphones
- Patch Cables For Loudspeakers
- What About Patch Bay Cables?
- Patch Cables For Eurorack & Modular Synths
- Related Questions
What Is A Patch Cable?
Before we get too far into this article, let’s define the term “patch cable”.
Patch cables (or patch cords) are generally what musicians call the 1/4″ cables that connect their instruments to their amplifiers or to mixing boards.
For guitarists and bassists, these patch cables are generally between 10 to 25 feet long and have TS (tip-sleeve) male connectors at each end.
For many of us guitarists (myself included), this is the definition of “patch cable”.
But that’s not technically correct. As guitarists, we use 1/4″ TS cables as our patch cords and so they are what we know to be patch cords but the term is actually much broader than that.
A patch cable is defined as any electrical (or optical) used to connect or “patch” one electronic (or optical) device to another.
So, then any signal carrying cable in audio, even the XLR microphone cables, are technically “patch cords”.
Related article: Why Do Microphones Use XLR Cables?
By that definition, the balanced 1/4″ TRS cables that carry audio from the [sometimes] balanced outputs of synthesizers are also patch cables. So, too, are the mic cables that carry audio from a microphone to a preamp; the unbalanced TRS 3.5mm (1/8″) cables that carry audio from a playback device to our headphones, and every other cable that carries audio from one device to another.
In this article, we’ll focus on the patch cables that carry audio from the following instruments:
There is, of course, much more to cover than this article will get into. I’ll link to other My New Microphone articles along the way to provide additional resources to further your knowledge.
Covering patch cables in the scenarios mentioned above will give us a solid understanding of the how patch cables carry audio.
Unbalanced Audio Vs. Balanced Audio
To really understand how patch cables carry audio, we must understand the difference between unbalanced and balanced audio transfer. This is a major differentiator in the design and performance of an audio cable.
What is unbalanced audio? Unbalanced audio is a system of carrying audio on two conductive wires within a cable. The signal wire carries the audio signal while the shield/ground wire acts as a return path to complete circuit; a shield from electromagnetic interference, and a ground wire if need be.
An unbalanced cable will tend to have the signal wire at the centre of its cross-section. There will be some insulation between the signal wire and the cylindrical frayed return/shield/ground “wire”. There will be more insulation and the outer protective layer at the outside of the connector.
So unbalanced cables only use two conductors. The ground wire simultaneously shields the signal wire from electromagnetic interference (EMI) noise and acts as an antenna, which picks up EMI noise.
Any noise picked up by an unbalanced cable is subjected to the audio signal. The more noise the unbalanced line induces, the worse the signal-to-noise ratio of the audio signal.
Having two conductors separated by insulation like this produces capacitance as well. The unbalanced cable conductors act a capacitor along the entire length of the cable and produce distributed capacitance.
This means that longer cables will have more capacitance.
Unfortunately, having capacitance in a cable causes a low-pass filter effect. The more capacitance (longer cable) causes a lower cutoff frequency for this filter.
This is why it’s important to use shorter unbalanced patch cables in our systems. This is particularly true with guitar, bass guitar and some synthesizers.
Unbalanced cables/connections include:
- Tip-Sleeve (TS): In Tip-Sleeve (TS) connectors, the tip is the signal wire and the sleeve is the ground wire.
- Unbalanced stereo Tip-Ring-Sleeve: Unbalanced stereo TRS has the unbalanced left audio channel on the tip, unbalanced right audio channel on the ring, and a common ground wire on the sleeve.
- Unbalanced mono Tip-Ring-Sleeve with DC bias: Some microphones (particularly lavaliers) require a DC bias voltage in order to function properly. TRS with DC bias has the tip as signal wire, the ring as DC bias wire, and the sleeve as the ground wire.
- Tip-Ring-Ring-Sleeve (OMTP standard): This “old” standard carried an unbalanced headset signal with the following wiring: Tip is for unbalanced headphone right audio channel, Ring 1 is for unbalanced headphone right audio channel, Ring 2 is for unbalanced microphone audio, and Sleeve is for ground.
- Tip-Ring-Ring-Sleeve (CTIA/AHJ standard): This “new” standard carries an unbalanced headset signal with the following wiring: Tip is for unbalanced headphone right audio channel, Ring 1 is for unbalanced headphone right audio channel, Ring 2 is for ground, and Sleeve is for unbalanced microphone audio.
- RCA: RCA has an inner pin that carries the audio signal and an outer shield that acts as the ground/shield/signal return wire.
Let’s focus on the TS connectors for a moment. We’ll start with a picture of the typical 1/4″ (6.35mm) TS cable used for guitars, bass guitar and many synthesizers and keyboards:
Look familiar? This phono connector is used to connect guitars, bass guitars, effects pedals, synthesizers, keyboards and even some microphones and other instruments.
Let’s have a look at a simplified schematic of the unbalanced connection:
As we can see, the signal is carried by the signal and return wires. The return/shield does block some EMI but, ultimately, noise will get into the signal.
The noise in the illustration above is overstated just to show that there will be some noise.
Either end of the unbalanced cable can be connected to ground if need be. This is sometimes the case at the mixer or amplifier end rather than the instrument end.
What is balanced audio? Balanced audio is a system of carrying audio using three conductive wires within a cable. Two signal wires carry the same signal in opposite polarities and are both relative to the ground/shield wire (which doesn’t carry signal). Balanced audio inputs require a differential amplifier to sum the differences between the signal wires to effectively use the signal.
So balanced audio requires three wires to function properly. The same signal is present in positive polarity on the hot/positive wire and negative polarity on the cold/negative wire. Each signal wire is referenced to a third wire that acts as a common ground.
The ground wire simultaneously shields the signal wires from EMI noise and acts as an antenna, which picks up EMI noise. Overall, the insulation and ground/shield wire reduce the amount of noise that is transferred to each of the signal wires.
A common design feature of balanced cables is the interweaving of the two signal wires into what is known as a twisted pair. A twisted pair of signal wires makes the induced noise more evenly distributed between the two signal wires.
So basically what ends up happening is the two signal wires end up with equal amounts of signal interference noise in the same polarity, but the signals are in opposite polarity.
When the balanced line is sent to a balanced input, a differential amplifier sums the differences between the two signal wires. This rids of the noise (which is the same on each wire) and adds the signals together (which are completely “out-of-phase” with one another). This process is known as common-mode rejection.
With common-mode rejection, we may run long balanced audio lines with little degradation in the audio signal due to noise or distributed capacitance!
Some synthesizers utilize balanced outputs. Professional microphones always use balanced audio.
Related article: Do Microphones Output Balanced Or Unbalanced Audio?
Balanced cables/connections include:
- 3-pin XLR: In XLR connectors, which are the standard for carrying balanced microphone audio, pin 1 is the ground wire, pin 2 is the positive audio wire, and pin 3 is the negative audio wire.
- Balanced Tip-Ring-Sleeve: In the balanced mono version of TRS, which isn’t very common for microphones (though XLR-balanced TRS adapters do exist), the tip is the positive audio wire, the ring is the negative audio wire, and the sleeve is the ground wire.
Let’s have a look at the TRS connectors for a moment. We’ll start with a picture of the typical 1/4″ (6.35mm) TRS cable used for some synthesizers and keyboards:
We see here that the ring provides an additional connection that coincides with the “negative polarity” signal wire within the cable.
Let’s have a look at a simplified schematic of the balanced connection:
We see above that the two signals are the same but in opposite polarity and that the ground wire does not carry a signal.
Noise will inevitably get on the signal wires. However, the noise, in a proper balanced cable, should be the same on each signal wire.
Remember that the balanced input has a differential amplifier. This amp sums up the difference between the two signal wires, effectively cancelling out the noise and preserving the full signal. In fact, the signal is even twice as strong due to the summing of two identical waveforms!
Now that we know about balanced and unbalanced audio, let’s get into the patch cables used in our typical instruments!
The Outputs Of Various Instruments
Patch cables connect the outputs of certain audio devices to the inputs of others. It’s important, then, to understand the nature of the outputs of various instruments and sound sources!
Let’s have a look at short table that lays out the output characteristics of various sources:
|Instrument Output||Mono/Stereo||Unbalanced/Balanced||Typical Impedance||Typical Level|
|Electric Guitar||Mono||Unbalanced||7 - 15 kΩ||Instrument Level
-20 dBu nominal
|Electric Bass Guitar||Mono||Unbalanced||7 - 15 kΩ||Instrument Level:
-20 dBu nominal
|Electric Keyboard||Mono or Stereo (dual mono)||Unbalanced or Balanced||10 - 15 kΩ||Line Level:
+4 dBu nominal
-10 dBV nominal
|Synthesizer||Mono or Stereo (dual mono)||Unbalanced or Balanced||10 - 15 kΩ||Line Level:
+4 dBu nominal
-10 dBV nominal
|Microphone||Mono or Stereo (dual mono)||Typically Balanced||50 - 600 Ω||Mic level:
-60 dBV to -20 dBV nominal
The table above gives us some hints as to the type of cable required to carry audio from the various instruments/sources. It also gives us some insight into the signal characteristics, which are good to know but not as important and the mono/stereo and unbalanced/balanced info.
If you’re interested in learning more about decibels in terms of audio (dB, dBV, dBu and more), check out my article What Are Decibels? The Ultimate dB Guide For Audio & Sound.
The Inputs Of Headphones And Loudspeakers
For playback, signals are typically patched into headphones and/or loudspeakers. Let’s have a look at their input characteristics in the table below:
|Transducer||Mono/Stereo||Unbalanced/Balanced||Typical Impedance||Typical Level|
|Headphones||Typically Stereo||Typically Unbalanced||10 - 300 Ω range nominal||Headphone/Line Level:
-10 dBV nominal
|Loudspeaker||Mono||Unbalanced||1 - 16 Ω nominal||Speaker Level:
0 dBV to 40 dBV nominal
Related article: How Do Speakers & Headphones Work As Transducers?
The Inputs And Outputs Of Other Audio Devices
Of course, our understanding wouldn’t be complete without knowing the characteristics of other I/O devices such as mixers, amplifiers, etc.
Let’s have a look at different inputs and outputs and how they are set up:
|I/O Type||Mono/Stereo||Unbalanced/Balanced||Typical Impedance||Typical Level|
|Mic Input||Mono||XLR: balanced||1.5 to 15 kΩ||Mic level:
-60 dBV to -20 dBV nominal
|Line Input (Consumer)||Mono||TS: unbalanced|
|10 kΩ to 50 kΩ||Line Level:
-10 dBV nominal
|Line Output (Consumer)||Mono||TS: unbalanced|
|75 to 600 Ω||Line Level:
-10 dBV nominal
|Line Input (Professional)||Mono||TS: unbalanced|
|10 kΩ to 50 kΩ||Line Level:
+4 dBu nominal
|Line Output (Professional)||Mono||TS: unbalanced|
|75 to 600 Ω||Line Level:
+4 dBu nominal
|Instrument Input||Mono or Stereo||TS: unbalanced|
|47 kΩ to over 10 MΩ||Instrument Level:
-20 dBu nominal
|Headphone Output||Stereo||TRS: unbalanced (stereo)||0.1 Ω to >120 Ω||Headphone level:
-20 dBV nominal
|Speaker Output||Mono||Most connectors: unbalanced||<0.1 Ω||<0 dBV|
The table above gives us a good idea of the various inputs and outputs we’ll encounter when patching audio equipment. Of course, we can really only rely on nominal or average levels. The actual signal characteristics can range greatly from device to device.
Patch Cables For Guitar And Bass
Alright, let’s get into the good stuff (and likely why you’re reading this article, to begin with). How do patch cables carry audio?
Let’s begin with guitar and bass guitar.
Electric guitars and acoustic-electric guitars utilize pick ups to turn their vibrating strings into electrical audio signals.
These pickups are mostly electromagnetic in nature though there are also some piezoelectric pickups on the market as well.
So the pickups produce electrical audio signals for the output of the guitar. This output is generally a 1/4″ unbalanced tip-sleeve jack.
The patch cable, then, for the vast majority of guitars and basses is the 1/4″ (6.35mm) TS cable.
These cables carry unbalanced mono audio signals.
Guitar amplifiers and pedals also utilize 1/4″ TS patch cables to patch amongst themselves.
Note that the frequency response of a guitar typically maxes out between 5 – 7 kHz and guitar amplifiers are generally not designed to produce frequencies beyond these points. Therefore, we can get away with some distributed capacitance (and the low-pass filtering that comes with it) in longer unbalanced cable runs.
Patch Cables For Keyboards And Synthesizers
Keyboards and synthesizers are instruments, though some output line levels signals rather than instrument level.
The outputs of many keyboards and synths are 1/4″ (6.35mm) jacks. The difference between these instruments and guitars/basses is that synths and keyboards often have stereo outputs (a jack for the left channel and the right channel). Many synths and keyboards will output mono if only the left output channel is patched.
The vast majority of synth and electric keyboard outputs are unbalanced and carry unbalanced audio signals.
Therefore, these instruments use 1/4″ (6.35mm) TS patch cables.
Note than, in many live scenarios where the cable runs are long, keyboards and synths will plug almost immediately into a DI to alter their unbalanced signals into balanced signals in order to travel the distance of cable without severe degradation.
Patch Cables For Microphones
Microphones output mic level signals. These signals are very low in level and are, therefore, very susceptible to noise.
On top of that, microphones are often tasked with capturing the full range of audible frequencies (from 20 Hz – 20,000 Hz).
So, then, we use balanced cables to maintain strong signal clarity and integrity.
These balanced cables are often XLR.
On top of carrying the balanced microphone signals, XLR cables can also provide phantom power to the microphone in question.
Other microphones, like lavalier mics, use other connections/cables and may even output unbalanced signals. However, most often we’ll be using XLR cables to patch microphones to mic preamps.
Patch Cables For Headphones
Headphones have a fairly wide variety of connectors though most often the cable carries unbalanced stereo audio.
Many headphones utilize 1/8″ (3.5mm) or 1/4″ (6.35mm) TRS cables and produce unbalanced stereo. Let’s have a look at how this works with the following illustration:
Headsets would typically use this unbalanced stereo setup with an addition wire to carry an unbalanced microphone signal in the opposite direction. These cables tend to have TRRS (tip-ring-ring-sleeve) connectors.
Other headphones, which are much less popular, utilize 2.5mm or 4.4mm connectors to carry [typically] unbalanced and stereo unbalances (with TS or TRRRS/tip-ring-ring-ring-sleeve), respectively.
Other headphones, like electrostatic headphones, use specialized multi-pin patch cables that can carry biasing voltage along with the audio signal.
I discuss each of these connection types is great detail in my article Differences Between 2.5mm, 3.5mm & 6.35mm Headphone Jacks.
To learn more about headphone cables and how they carry audio, check out my article An In-Depth Look Into How Headphone Cables Carry Audio.
Patch Cables For Loudspeakers
Patch cables for loudspeakers feature plenty of variation in connector types (banana plugs, Neutrik, spade , pin connectors, etc.).
Most speaker cables, however, will carry unbalanced mono audio.
The voltages within speaker cables are so high that we don’t really need the noise advantages of balanced cables. In other words, speaker level signals are so strong that any resulting noise would be minimal (though it would be considerable with a low-level mic signal).
This high voltage also often requires thicker gauge cables and unbalanced (2-wire) cables are simpler and cheaper to produce and use.
So speaker cables generally carry unbalanced mono and are thicker in order to handle the relatively high levels (voltages) of speaker signals.
What About Patch Bay Cables?
The patch bay is another important piece of equipment we should discuss when talking about patch cables. I mean, the term “patch” is in the name!
Patch bays can be incredibly useful for signal routing in professional studios where the studio system is large and complex. The bay makes it easy to route and re-route signals without having to get behind large mixing boards or other units.
Patch bays come in balanced (common) and unbalanced (less common) varieties. Generally speaking, the manufacturer will let us know in the product name whether they bay is either or.
Often times patch bays will opt for 1/4″ TRS inputs and outputs and, therefore, will use 1/4″ (6.35mm) balanced TRS patch cables.
These cables will carry balanced audio or unbalanced audio, if need be. They will also have the ability to carry phantom power to microphones further up the line. Be careful not to “hot patch” (remove or plug in patch cables while phantom power is engaged as it may cause a short circuit and damage the microphone)!
Other patch bays may use other cables (XLR, DB25, or others) but more often than not we’ll find that they use 1/4″ cables.
Patch Cables For Eurorack & Modular Synths
Before we wrap up, let’s quickly discuss Eurorack modular synthesis!
Eurorack modules and other modular synth units typically patch together via unbalanced 1/8″ (3.5mm) TS cables.
The smaller footprint (relative to 1/4″) allows for more compact modules and more patching per square inch.
What are the different types of audio cables? Audio cables come in a variety of inner conductor designs and pin layouts with plenty of different connectors. Let’s discuss the “universal” types since there are too many proprietary connections (new and legacy) to list them all accurately.
Audio cable wiring formats vary wildly. Each signal path can be unbalanced or balanced; there can be one or more channels (mono, stereo, or more); there can be conductors/pins dedicated to carrying power; there can be signal travelling in both directions (think headsets). There are even cable snakes that combine several individual cables into one larger cable.
To learn more about audio snakes, check out my article What Is An Audio Snake And Are They Required?
Audio cable connector types:
- XLR 3-pin
- XLR 4-pin
- XLR 5-pin
- XLR 6-pin
- XLR 7-pin
- TQG “Mini XLR”
- TA3 “Mini XLR”
- TA4 “Mini XLR”
- TS 2.5mm
- TS 3.5mm (1/8″)
- TS 6.35 (1/4″)
- TRS 2.5mm
- TRS 3.5mm (1/8″)
- TRS 6.35mm (1/4″)
- TRRS 2.5mm
- TRRS 3.5mm (1/8″)
- TRRS 6.35mm (1/4″)
- TRRRS 4.4mm
- Switchcraft 2501F
- Amphenol Tuchel
- Mobile High-Definition Link
- 30-Pick Dock
- Five-Way Binding Post
- Fahnestock Clips
Are XLR cables better than TRS? XLR and TRS cables both carry balanced mono audio (or unbalanced stereo audio). XLR has the benefit when making a patch/connection since ground (pin 1) connects first with pins 2 and 3 (hot and cold) connecting simultaneously afterward. TRS cables connect one pin at a time which can cause short circuits while being connecting/disconnected. If that’s not an issue, then TRS benefits greatly from having a smaller form factor, allowing more connections to be made per given area.