Audio Cables & Wiring

All tangled up when it comes to audio leads? Here are the answers to the most common queries on the subject from SOS readers.

All audio signal cable is screened, which means that an outer conductor wraps around the other conductor(s) to shield them from electromagnetic interference. The outer screen, which may be made of wire braid, metal foil or conductive plastic, is usually connected to ground so that any induced currents (due to interference) flow directly to ground rather than being allowed to modulate the audio signal. However, screening isn't a perfect solution, which is why balancing was invented.

In an unbalanced cable, there's a single inner core that carries the signal while the outer screen also doubles as the signal return path. Any interference that results in induced currents flowing through the screen conductor will cause these currents to be added to the wanted signal, so some interference problems are still possible, especially with long cable lengths or where there are nearby sources of strong interference. Though it's not often realised, screened cable offers very little protection against induced hum, as the cable is actually acting like a single-turn transformer, coupling energy from other mains conductors and transformers in the vicinity.

In a balanced cable, there are two inner conductors, often known as hot and cold. The screen is grounded, as before, but this time the screen is not part of the signal path. More importantly, balanced equipment is designed so that its hot and cold outputs carry the same signal but with the cold signal phase inverted with respect to the hot signal. At the receiving end, the balanced input stage re-inverts the cold signal and adds it to the hot signal, thus restoring the original signal. The clever part is that any interference that makes it through the screen is likely to have virtually the same influence on the hot and the cold conductors (as they are in more or less the same place).

As a phase reversal is implemented at the input of the receiving piece of equipment, any interference common to both conductors will cancel out. The effectiveness of this system depends, amongst other things, on how well balanced the hot and cold arms of the circuitry are at either end of the cable. Mic amps often have a specification for common mode rejection, which is a measure of how effectively the circuitry rejects interference that is common to both hot and cold inputs.

A further type of cable known as Star Quad was developed to further improve the immunity to interference, and this works by having two pairs of internal cables wired in parallel, but spaced (actually woven or plaited) so that any interference induced due to the cable cores not occupying exactly the same position in space is largely cancelled out. Star Quad seems to be used mainly in live sound applications where long cable runs are commonplace, but it is demonstrably more effective than conventional balanced cable.

Foil or braid screened cables tend to be good from a screening point of view, whereas the type of cable that uses a bunch of unbraided wires wrapped around the outside is less effective, especially if the cable is bent in such a way as to open a space in the screen. Another popular type uses a conductive plastic screen where a metal wire runs alongside the screen to permit connection. Over short distances at line level, most types of screening are adequately effective, though a woven metal screen or a foil screen is likely to be more effective than a conductive plastic or wrapped wire screen.

Microphone cable choice is particularly important, as some cables can generate electrical noise when moved or bent. A woven screen cable designed specifically for use with microphones probably offers the most effective screening, coupled with low handling noise, but conductive plastic is also an effective solution for the cable lengths used in a typical small studio. Conductive plastic has an inherently low handling noise and is available in a range of colours that can help identify which microphone is connected where.

Foil-screened cables are rather rigid and don't take kindly to sharp bends, but they do offer excellent screening properties and smaller-gauge cables are available for such jobs as patchbay wiring and permanent cable runs. Many multicore cables also use foil screening, and it's important not to coil such cables too tightly.

There are no impedance issues with audio signal cables at the lengths used within studios, but you should take into account the fact that mic cables need a combination of good screening and low handling noise. Ease of termination and cable clamping may also be an issue.

No. You can use a balanced dynamic microphone with phantom power switched on, but the only way to connect an unbalanced source to the same system is to feed it through a balancing transformer first. If you were to connect an unbalanced cable, you would short out one side of the phantom power supply, and though a properly designed phantom supply will be protected against damage in this way, it's not recommended. More seriously, some or all of the phantom power voltage will be applied to the pins of the unbalanced device and this may cause damage to some studio units.

The traditional method is to use balanced cable and connect the cold to the screen at the unbalanced end. However, this can sometimes result in ground loop hum problems, so it is safer to connect the unbalanced end of the cable as follows.

Connect the screen to the ground pin via a resistor of between 100Ω and 500Ω or leave it disconnected altogether. Connect the cold core of the cable to the connector pin normally used to connect the screen. Connect the hot core to the connector pin normally used to connect the hot conductor.

Many people do, and get away with it, but it really isn't a very good idea, as you can end up with clicks and glitches that seem to have no apparent cause. At the high frequencies needed to carry digital signals, cable impedance has a significant effect on the shape of the waveform being transmitted, and S/PDIF signals ideally need to be fed via a 75Ω cable designed specifically for digital data use.

If the cable and terminating impedance aren't correct, energy is reflected back down the cable, which has the effect of degrading the shape of the digital pulses. Poor quality connectors can also compromise the performance, so this is one instance where even the accomplished solderer of cables might be better off buying a ready-made cable of the right length. At longer cable lengths, it becomes even more important to choose a high quality digital cable and, as a rule, cable runs should be kept as short as is practical.

AES-EBU signals are more tolerant, though special cable (in this case 100Ω) is available for this format too. In the absence of a dedicated digital cable, conductive plastic screened microphone cables generally produce good results over short to medium distances.

You'll need to check your equipment manual for this one, as the way you wire the cable depends on the design of the balanced output stage. In some cases you need to link the cold and screen pins at the balanced end (if the output stage is 'fully floating') while in others you must leave the cold pin disconnected. In situations that require the latter approach, you will probably find that the signal level is 6dB lower than when using the equipment balanced. This is because you're only using one half of the signal from the output stage.

Mains cables carry relatively high alternating currents that can be induced into audio cables running alongside them, even if the audio cable is well screened. The longer the distance the cables run alongside each other, the greater the amount of interference (usually hum) that will be induced into the signal cable. When audio and mains cables must cross, try to arrange the crossing to be at right angles, as this is the angle of minimum coupling.

This is one of those 'how long is a piece of string?' questions because the answer depends on both the cable type and on the impedance of the circuitry at either end. As a very general rule, high-impedance mics or feeds from high-impedance instrument pickups shouldn't be longer than around four or five metres, as the cable capacitance can cause the high frequencies to be attenuated, but low-impedance balanced mic cables can be tens or even hundreds of metres long if the sending and receiving devices are designed properly and the source impedance is very low. With semi-pro equipment, keeping balanced mic or line cables down to 10 or 20 metres maximum would be sensible, though it's still best to keep all cable runs as short as you can.

Speaker cable needs to have a very low electrical resistance, so it needs to be fairly hefty and made from a pure material, such as oxygen-free copper (OFC). Impure material can introduce nonlinearities (the oxidised copper actually behaves as a semiconductor) that manifest themselves as increased distortion at low signal levels. There are many cables that qualify, including 30A 'cooker' mains cable, but a sensibly priced, heavy-duty speaker cable is easier to use and looks nicer. If the cable resistance is more than a tiny fraction of an Ohm, the amplifier's damping factor is compromised and also the loudspeaker's frequency response can be affected. The reason for this is that a loudspeaker's impedance varies with frequency, but if this impedance is placed in series with a significant fixed cable resistance it acts as a potential divider, and the power delivered to the loudspeaker at different frequencies will be altered slightly.

Exotic cables can have an effect when used with different speakers, as the cable inductance and inter-cable capacitance can influence the crossover performance to some small degree. As a rule, though, the difference is so small that you're better off spending your money where it makes a real difference. Buy good cable, but don't waste money on 'fairy dust'. Keep speaker cables in stereo or surround systems the same length, but no longer than is necessary. Good-quality, low-resistance connectors will also improve performance.

Active speakers can be connected up using regular balanced mic cables, and the cable type will have no significant effect on the audio quality.

A typical 'Y' lead has a conventionally wired stereo jack at one end of a run of balanced (twin cored cable), but at the other end, the cable splits so that the screen and hot core are wired to one mono jack and the screen and cold core are wired to another.

The principle of operation is that each of the two cable cores carries one unbalanced signal, one from the mixer insert point to the external device, and one from the external device back to the mixer. Which way round the two connectors go depends on how the mixer manufacturer wires their insert points -- tip (tip of the jack plug) send or tip return. Check your mixer manual to find out, and then label the two mono plugs accordingly. If you don't enjoy soldering, some companies make off-the-shelf 'Y' cables.

Thanks to Canford Audio (www.canfordaudio.com) for supplying many of the cables used to illustrate this article.

Thankfully, hooking up audio and AV systems is much more straightforward than it used to be. For most people, home entertainment systems no longer consist of large racks of individual components hiding a rat’s nest of wires and connectors, and we’re better off for it. But there are still times you need to connect audio hardware devices, and if you need to source cables (cords), connectors, or adapters, knowing the specific names of each type is necessary. Let’s go over the ones you’re most likely to encounter.

Editor’s note: This post was updated on July 7, 2023, to account for changes in our house style and formatting standards.

How do I connect my headphones?

The two most common sizes of TRS jack connectors.

Wired headphones connect to a playback device’s analog headphone socket using a jack plug. Suppose they’re standard stereo headphones with no microphone. In that case, it’s a three-terminal tip-ring-sleeve (TRS) connector, easily identified by the two insulating bands (usually black) on the barrel of the jack. These are commonly found in two sizes. The smaller size found on portable devices is referred to as a minijack, or by its diameter, 3.5mm. It’s sometimes called a 1/8-inch jack in the US, though that’s an approximation. The larger size of headphone jack you’ll find is commonly known as a 1/4 inch (or 6.3mm) jack plug. Adapters are easy to find to change one size jack plug to the other.

This earphone’s cable terminates into a 90-degree TRRS jack.

Wired headphones with a microphone built-in use a modified version of the same-sized minijack plug but with an additional electrical terminal (to carry the mic signal) in the form of an extra ring, making it a tip-ring-ring-sleeve (TRRS) connector, which has three insulating bands visible on the barrel.

How do I connect my headphones when there’s no jack socket?

These end in a 3.5mm connector, so you’ll need to use a stupid dongle on new phones.

Since smartphones have abandoned the headphone jack, you have three options. If you already have wired headphones you want to use; you’ll need a special adapter (a dongle) to connect to the phone’s system connector (a Lightning connector on iPhones or USB-C for basically everything else) and provide you with the analog 3.5mm headphone socket you need to plug in your headphones. These are also referred to as digital-to-analog converters (DACs).

If you want to stick with wired (for reasons) and don’t want to deal with dongles, you can get a set of wired USB headphones to plug directly into your phone. If you prefer to avoid dealing with dongles or wires, you can also go down the wireless, Bluetooth route.

What are the other types of headphone connectors called?

The Drop+Ether CX closed-back headphones come wired with a four-pin XLR for differential drive.

You may have run into premium headphones with other jack sizes, different pin configurations (4.4mm Pentaconn), or larger XLR-type connectors. These are required to run your headphones in a balanced or differential drive configuration.

What connectors are used at the headphone end of the cable?

The cable plugs into the bottom of each ear cup via 2.5mm jacks.

When the cable is removable, the plugs used at the headphone end vary quite a bit, and we won’t cover them all here. 3.5mm jacks with a twist-to-lock system are relatively common. You’ll also find 2.5mm TRS jack plugs on some headphones (Bose, for example), while others have 2.5mm TS jack inputs at the bottom of each ear cup for the wires to connect to (the Monoprice Monolith M1060, for example). Premium headphones can use mini XLR connectors; some use propriety connectors like Sennheiser‘s two-pin push-fit connector.

The MMCX connectors are gold-plated and fit snugly into the SE215 female input.

Many in-ear monitor (IEM) headphones employ micro-miniature coaxial (MMCX) connectors. As the name implies, this connection standard is small enough to fit into a pair of in-ear monitors easily. These are used mainly for better-engineered in-ear monitors, where having a replaceable cable means the headset doesn’t become trash if the cable fails. Plus, the connection itself locks into place and allows for 360 degrees of rotation, so not only does it make the cable easier to replace, but it also makes it harder to break in the first place.

What else are jack plugs used for?

Jack plugs are also used to connect audio signals at “line level” in several contexts. 3.5mm TRS minijacks are found at the ends of the standard auxiliary (“aux”) cable to connect your phone directly to a portable speaker or car stereo system. The larger 1/4-inch plugs are used in semi-professional applications to connect signals using TS plugs (unbalanced applications) or TRS plugs (balanced applications).

What are XLR connectors?

XLR cables are used for microphones and other pro audio applications.

XLR connectors carry the tiny electrical signals produced by microphones and in other instances where signal integrity is essential — typically professional audio environments. Microphones have male outputs, and mic preamps have female input connectors on the front; hence, the standard XLR cable has a female on one end and a male on the other. The locking connectors are relatively large and heavy, explicitly designed for carrying balanced signals and wired using balanced (microphone) cable. This cable type is well suited to longer cable runs, as they have better shielding and noise rejection abilities.

What are RCA connectors?

RCA-type plugs are usually color-coded red (right) and white (left) for stereo interconnection.

RCA (or phono) connectors are smaller cinch-type connectors used in interconnects for connecting “line level” audio signals in consumer products. You’ll likely recognize the red and white color-coded stereo cables from their use in connecting older hifi system components or the yellow plugs that carry analog video signals to TVs from old DVD players, VCRs, or video game consoles. Since they can only carry unbalanced signals, they’re only suitable for relatively short-distance transmission of audio and video signals. They are still reasonably common, particularly for connecting record player turntables to phono input stages or connecting home theater subwoofers. They are also used for coaxial, digital audio connections (see the section later on).

Unlike a lot of connectors, the RCA name isn’t derived from a particular physical aspect of the connection. It’s named after the Radio Corporation of America, which developed and introduced the standard in the 1930s.

What connectors are used for speaker cables?

Speaker wire comes in different gauges and can be terminated with bare connections or connectors like these gold-plated banana plugs.

Unless you’re hooking up a PA system, the primary connector you’ll likely need to connect your speakers is the banana plug, shown above on the right. Many speakers have binding posts or terminal clamps that will accept the bare ends of the speaker wire. If that’s the case, connecting the positive terminal at the source (amplifier) to the corresponding terminal on your speaker is essential to keep everything in phase. Most speaker wire has an identifying mark on one of the conductors to help you keep track of what’s what.  In some smaller powered speaker systems, the cable that connects the left and right speakers uses RCA (phono) connectors, as shown below.

Active loudspeakers have built-in amplifiers and require a power source.

How is speaker wire different from regular stereo wire?

Stereo interconnects, which usually have red and white (or red and black) labeled RCA connectors on the ends, are intended for low audio voltages (line level) with low current, and have a central insulated conductor surrounded by a shield (ground) for each channel (left and right).

Speaker cable, or speaker wire, consists of a pair of conductors surrounded by an insulating, flexible PVC or similar material that either has bare ends or banana plugs (see above) at the end. This cable should be specified to carry the power needed to drive loudspeakers to produce sound. Heavier gauge wire is required for higher power, and cables should always be kept as short as possible. As long as these basic requirements are met, there’s no point in spending a lot of money on cables, as this past experiment demonstrates.

How are digital connections different from analog ones?

Digital audio connections transfer signals between devices without converting them to analog and back again, which means the quality is preserved. Another bonus is that digital signals are less susceptible to sources of noise and interference, which makes cable quality even less of a concern than with analog.

What type of wire do I need for a digital audio connection?

HDMI cables carry up to 32 channels of digital audio.

Standard consumer-level wired stereo digital connections, often labeled “coax”(pronounced co-axe, not like the word coax), use the same RCA connectors we discussed previously, specifically with 75ohm coaxial cable. Home theater and AV systems are more likely to use high-definition multimedia interface (HDMI) cables, which also carry digital video signals. These allow eight or 32 audio channels (for HDMI version 2 and above) for surround systems, including Dolby ATMOS, and offer bidirectional capabilities in the form of HDMI ARC and eARC.

What are optical connections for?

An optical cable can transmit stereo digital audio signals.

Optical cables (also called TOSLINK) carry digital audio between devices in much the same way as a wired coax connection, using light to represent the binary data instead of electrical voltage levels. These are preferred in most applications for stereo as they provide electrical isolation between devices, and they can also carry up to eight audio channels in multichannel applications.

If you’re looking to transfer audio between devices, these are the most common ways, depending on the type and age of equipment you’re looking to connect. Hopefully, this has helped, and now whether you’re looking to listen to music wirelessly or hook up a state-of-the-art soundbar, you’ll know what you need to do it.