Audio Connectors, Cables, and Signal Formats

Different audio connectors and cables are suited for different purposes. They are available for professional and consumer audio equipment, at a range of prices and levels of quality. Audio connectors are often indicative of the kind of signal they transmit. However, there are enough exceptions that it’s important to know what kind of audio signal you are connecting, in addition to the connector type. An important distinction is whether an audio connector carries a balanced or an unbalanced signal. When connecting microphones and musical instruments to an audio interface or a mixer, make sure the interface has the proper input jacks for the type of connectors and cables you plan to use.

Analog Audio Connectors, Cables, and Signal Formats

The following is a cross-section of available industry-standard analog audio connectors, cables, and signal formats.

1/8" Mini Connectors

These are very small, unbalanced audio connectors. Many computers have 1/8" mini inputs and outputs at -10 dBV line level, and many portable audio devices such as CD players, iPod digital music players, and MP3 players use these connectors for headphone outputs. Portable MiniDisc and DAT recorders often use 1/8" mini connectors for connecting microphones.

Figure. Illustrations showing mono and stereo miniplug connectors.

Note: Some Macintosh computers and portable audio recorders also use a connector that combines both a stereo miniplug and a 1/8" optical digital connection (see the information about S/PDIF in Digital Audio Connectors, Cables, and Signal Formats) in a single jack.

RCA Connectors

Most consumer equipment uses RCA connectors, which are unbalanced connectors that usually handle –10 dbV (consumer) line levels. RCA connectors are used on consumer audio equipment such as home stereo systems and videocassette recorders.

Figure. Illustration showing RCA connector.

1/4" Audio Connectors

1/4" connectors (sometimes called phone plugs) are used on a wide variety of professional and consumer musical equipment, including musical instruments and amplifiers, speakers, and external effects devices.

1/4" Tip-Sleeve Connectors

1/4" tip-sleeve (TS) connectors with a tip and a sleeve are unbalanced connectors often used for musical instruments like electric guitars, keyboards, amplifiers, and so on.

Figure. Illustration showing 1/4" tip-sleeve connector.

1/4" Tip-Ring-Sleeve Connectors

Professional equipment often uses 1/4" tip-ring-sleeve (TRS) audio connectors with +4 dBu line level. 1/4" TRS connectors connect to three wires in an audio cable—hot, neutral, and ground—and usually carry a balanced audio signal. In some situations, the three wires may be used to send left and right (stereo) signals, making the signals unbalanced.

Figure. Illustration showing 1/4" tip-ring-sleeve connector.

Note: Tip-sleeve and tip-ring-sleeve connectors look almost identical. Some audio devices (especially mixers) accept a TS connector in a TRS jack, but you should always check the equipment documentation to be sure. Remember that most 1/4" TS connectors connect to –10 dBV line level equipment, whereas 1/4" TRS connectors usually expect a +4 dBu line level.

XLR Connectors

These are the most common professional audio connectors. They almost always carry a balanced signal. Many cables use an XLR connector on one end and a 1/4" TRS connector on the other. The signal may be microphone level (when using a microphone) or +4 dBu/dBm (professional) line level.

Figure. Illustration showing an XLR connector.

Digital Audio Connectors, Cables, and Signal Formats

Although digital audio signals are completely different from analog signals, the same connectors are often used for convenience. For example, an XLR connector can be used to carry an analog audio signal or an AES/EBU digital audio signal. The following is a cross-section of available industry-standard digital audio connectors, cables, and signal formats.

S/PDIF

Sony/Philips Digital Interface Format (S/PDIF) is a consumer-level variation of the AES/EBU digital audio protocol. S/PDIF audio data can be transmitted several ways, including:

  • Via coaxial cables with an RCA connector

  • Via optical TOSLINK

Connectors for S/PDIF signals are found on most consumer digital equipment, such as DAT recorders, CD players, DVD players, MiniDisc equipment, and some audio interfaces.

Figure. Illustration showing an S/PIDF optical digital connector.

TOSLINK Optical and ADAT Lightpipe

TOSLINK is a connector for optical digital signals. TOSLINK is used for several digital signal formats, although most devices support only one of these formats:

  • S/PDIF (stereo digital)

  • AC-3 and DTS (5.1-channel surround)

  • ADAT Lightpipe (an 8-channel digital signal)

Some Macintosh computers have a single interface that combines a TOSLINK connector with an analog stereo miniplug.

Figure. Illustration showing a TOSLINK connector.

ADAT Lightpipe is an eight-channel digital audio format developed by Alesis. This signal format uses TOSLINK optical connectors. Eight channels are supported at sample rates of 44.1 and 48 kHz using 24 bits per sample. Higher sample rates are available by pairing channels (this format is sometimes called sample multiplexing, or S/MUX). For example, a sample rate of 192 kHz is possible, but the number of channels is reduced to two. However, not all equipment supports channel pairing and increased sample rates.

AES/EBU

The AES/EBU (Audio Engineering Society/European Broadcasting Union) standard for transferring digital audio typically uses XLR connectors in professional studio environments. The data protocol is essentially identical to S/PDIF.

Figure. Illustration showing an XLR connector.

TDIF Connectors

Tascam Digital Interface (TDIF) is a signal format for transferring digital audio between Tascam digital multitrack recorders or digital mixers. Connections are made via a 25-pin D-subminiature connector and data is carried on shielded cable. Eight channels are supported at sample rates of 44.1 and 48 kHz using 24 bits per sample. Higher sample rates are available by pairing channels. The TDIF standard is currently one of two major formats (the other being ADAT optical) widely used in professional products for digital transfer of more than two tracks of audio simultaneously using only one cable.

Figure. Illustration showing a TDIF connector.

About Microphone, Instrument, and Line Level

Audio equipment can output line level at –10 dBV (consumer level), +4 dBm/dBu (professional level), or microphone level, which is around 50 or 60 dB less than line level. When you use a microphone, the level is very low, requiring a preamplifier to raise the signal to line level before it can be recorded or processed. Most audio mixers, cameras, and professional portable recording devices have built-in preamplifiers.

Instrument level is between microphone and line level, around –20 dBV or so. Guitars and keyboards usually output at instrument level.

Signal Differences Between Pro and Consumer Equipment

Professional audio equipment typically uses higher voltage levels than consumer equipment, and it also measures audio on a different scale.

  • Professional analog devices measure audio using dBu (or dBm in older equipment). 0 dB on the audio meter is usually set to +4 dBu, which means optimal levels are 4 dB greater than 0 dBu (.775 V), or 1.23 V.

  • Consumer audio equipment measures audio using dBV. The optimal recording level on a consumer device is –10 dBV, which means the levels are 10 dB less than 0 dBV (1 V), or 0.316 V.

Therefore, the difference between an optimal professional level (+4 dBu) and consumer level (–10 dBV) is not 14 dB, because they are referencing different signals. This is not necessarily a problem, but you need to be aware of these level differences when connecting consumer and professional audio equipment together.