Jack plug
From Wikipedia, the free encyclopedia
A jack plug (UK) is a common audio connector. The terms phone plug (U.S.), and phone jack for the corresponding socket or jack, are also used for these connectors, especially for the original 1/4" size. Note that this is in contrast to the terms phono plug and phono jack which normally refer to RCA connectors. Phone plugs were originally used in telephone switchboards and should not be confused with the registered jack-series plugs used to connect telephones to wall outlets.
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[edit] Modern jack plugs
Modern jack plugs are available in three standard sizes. The original 1/4" (6.35 mm) version dates from 1878, for use in manual telephone exchanges—making it possibly the oldest electrical connector standard still in use. The 3.5 mm or miniature and 2.5 mm or subminiature sizes were originally designed as two-conductor connectors for earpieces on transistor radios. The 3.5 mm and 2.5 mm sizes are also referred to as 1/8" and 3/32" respectively in the United States, though those dimensions are only approximations. All three sizes are now readily available in two-conductor (mono) and three-conductor (stereo or tip ring sleeve) versions.
Four and five conductor versions of the 3.5 mm plug are used for certain applications. A four conductor version is becoming a de facto standard output connector for compact camcorders, providing stereo sound plus a video signal. This interface is also seen on some laptop computers. Proprietary interfaces using both four and five conductor versions exist, such as the audio connector on the first four generations of iPod MP3 players (the 5th generation player now uses a standard 3 conductor cable), where the extra conductors were used to supply power for accessories. There is also an optical connector used for TOSLINK (mainly on things like portable equipment, hi-fi separates and similar tend to use the standard square connector) that is the same size as a 3.5 mm jack. Sockets exist that can make either an optical connection to such a plug or an electrical connection to a stereo jack plug.
Both two-conductor and three-conductor versions of the three standard sizes are readily available in male (plug) and female (socket or simply "jack") line versions, and panel-mounting female versions. Panel-mounting male versions of these also exist but are rare, as they are vulnerable to mechanical damage and therefore unreliable. Female line versions are also notoriously unreliable and are avoided by many users.
The most common arrangement remains to have the male plug on the cable, and the female socket mounted in a piece of equipment, which was the original intention of the design. A considerable variety of line plugs and panel sockets is available, including plugs suiting various cable sizes, right angle plugs, and both plugs and sockets in a variety of price ranges and with current capacities up to about 15 amperes for the 1/4" version.
Non-standard sizes, both diameters and lengths, are also available from some manufacturers, and are used when it is desired to restrict the availability of matching connectors.
Several obsolete versions of the 1/4" jack plug exist, including:
- A two-pin version, consisting of two mono 6.3 mm jack plugs at a centre spacing of 1". The socket versions of these can be used with normal jack plugs provided the plug bodies are not too large, but the plug version will only mate with two jack sockets at 1" centre spacing, or with line sockets, again with sufficiently small bodies. These connectors were commonly used on early stereo tape recorders. A similar type of 3.5 mm connector is often used in the armrests of aircraft, as part of the on-board entertainment system. It is intended to frustrate flyers from using personal headphones on planes, and encourage rental of proprietary airline headphones (when rental is necessary). Plugging a stereo plug into one of the two mono jacks typically results in the audio coming into only one ear. Adaptors are available.
- A short-barrelled version, once used on high-impedance mono headphones, and in particular those used in World War Two aircraft. It is physically possible to use a normal plug in a short socket, but a short plug will neither lock into a normal socket nor complete the tip circuit. These are still manufactured but are now regarded as a non-standard size.
[edit] Mono and stereo compatibility
At the top is a three-conductor jack from the same era.
In the original application in manual telephone exchanges, many different configurations of 1/4" jack plug were used, some accommodating five or more conductors, with several tip profiles. Of these many varieties, only the two-conductor version with a rounded tip profile was compatible between different manufacturers, and this was the design that was at first adopted for use with microphones, electric guitars, headphones and many other items of audio equipment.
When a three-conductor version of the 1/4" jack was introduced for use with stereo headphones, it was given a sharper tip profile in order to make it possible to manufacture jacks (sockets) that would accept only stereo plugs, to avoid short-circuiting the right channel amplifier. This attempt has long been abandoned, and now the normal convention is that all plugs fit all sockets of the same size, regardless of whether they are mono or stereo. Most 1/4" plugs, mono or stereo, now have the profile of the original stereo plug, although a few rounded mono plugs are also still produced. The profiles of stereo miniature and subminiature plugs have always been identical to the mono plugs of the same size.
The results of this physical compatibility are:
- If a two-conductor plug of the same size is connected to a three-conductor socket, the result is that the ring (right channel) of the socket is grounded. This is deliberately used in several applications, see "tip ring sleeve", below. However it may also be dangerous to the equipment if the result is to ground (short circuit) the output of the right channel amplifier.
- If a three-conductor plug is connected to a two-conductor socket, normally the result is to leave the ring of the plug unconnected (open circuit). In the days of valves ("tubes" in the U.S.) this was also potentially dangerous to equipment but most solid state devices tolerate this condition well. A stereo socket could be wired as a mono socket but to ground the ring in this situation, but the more conventional wiring in this case is to leave the ring unconnected, exactly simulating a mono socket.
[edit] Uses
Some common uses of jack plugs and their matching jacks are:
- Headphone and earphone jacks on a wide range of equipment. 1/4 in. plugs are common on standalone equipment, while 3.5 mm plugs are nearly universal for portable audio equipment. 2.5 mm plugs are not as common, but are sometimes used on communication equipment such as two-way radios and mobile phones.
- Microphone inputs on tape and cassette recorders, sometimes with remote control switching on the ring.
- Patching points on a wide range of equipment.
- Personal computer sound cards. Stereo 3.5 mm jacks are used for:
- Line in (stereo)
- Line out (stereo)
- Headphones/loudspeaker out (stereo)
- Microphone input (mono, sometimes with 5v power available on the ring)
- Electric guitars. Almost all electric guitars use a 1/4 in mono jack (socket) as their output connector. Some makes (such as Shergold) use a stereo jack instead for stereo output, but more commonly a second mono jack is provided (as with Rickenbacker).
- Instrument amplifiers for guitars, basses and similar amplified musical instruments. 1/4 in jacks are overwhelmingly the most common connectors for:
- Inputs. A shielded cable with a mono ¼ in jack plug on each end is commonly called a guitar cord or a patching cord, the first name reflecting this usage, the second the history of the jack plug's development for use in manual telephone exchanges.
- Loudspeaker outputs, especially on low-end equipment. Speakon connectors are generally considered superior and so are usually preferred on higher-end equipment, although it is not uncommon common to find both provided for compatibility.
- Line outputs.
- Foot switches and effects pedals. Stereo plugs are used for double switches (for example by Fender). There is little compatibility between makers.
- Effects loops, which are normally wired as patch points.
- Electronic keyboards use jacks for a similar range of uses to guitars and amplifiers, and in addition
- Sustain pedals.
- Electronic drums use jacks to connect sensor pads to the synthesizer module or MIDI encoder. In this usage, a change in voltage on the wire indicates a drum stroke.
- Some compact and/or economy model audio mixing desks use stereo jacks for balanced microphone inputs.
- The majority of professional audio equipment uses mono jacks as the standard unbalanced input or output connector, often providing a ¼ in unbalanced line connector alongside (or in a few cases in the middle of!) and as an alternative to an XLR balanced line connector.
- ¼ in stereo connectors are used to connect external processing devices to mixing consoles' insert points (see Insert (effects processing)). An unbalanced signal can be both sent and recieved using a single connector.
- Some small electronic devices such as audio cassette players, especially in the cheaper price brackets, use a two-conductor 3.5 mm or 2.5 mm jack as a DC power connector.
- Some photographic studio strobe lights have ¼ in or 3.5 mm jacks for the flash synchronization input. A camera's electrical flash output (PC socket or hot shoe adapter) is cabled to the strobe light's sync input jacks. Some examples: Calumet Travelite, and Speedotron use a ¼ in mono jack as the sync input; White Lightning uses ¼ in stereo jacks; Pocket Wizard (radio trigger) and Alien Bees use 3.5mm mono jacks.
- Several types of graphing calculators use the 2.5 mm jack as a serial port.
[edit] Switch contacts
Panel-mounting jacks are often provided with switch contacts. Most commonly, a mono jack is provided with a single normally closed (NC) contact, which is connected to the tip (live) connection when no plug is in the socket, and disconnected when a plug is inserted. Stereo sockets commonly provide two such NC contacts, one for the tip (left channel live) and one for the ring or collar (right channel live). Some designs of jack also have such a connection on the sleeve, as this contact is usually ground it is not much use for signal switching but could be used to indicate to electronic circuitry that the socket was in use.
Less commonly, some jacks are provided with normally open (NO) or change-over contacts, and/or the switch contacts may be isolated from the connector.
The original purpose of these contacts was for switching in telephone exchanges, for which there were many patterns. Two sets of change-over contacts, isolated from the connector contacts, were common. The more recent pattern of one NC contact for each signal path, internally attached to the connector contact, stems from their use as headphone jacks. In many amplifiers and equipment containing them, such as electronic organs, a headphone jack is provided that disconnects the loudspeakers when in use. This is done by means of these switch contacts. In other equipment, a dummy load is provided when the headphones are not connected. This is also easily provided by means of these NC contacts.
Other uses for these contacts have been found. One is to interrupt a signal path to enable other circuitry to be inserted. This is done by using one NC contact of a stereo jack to connect the tip and ring together when no plug is inserted. The tip is then made the output, and the ring the input, thus forming a patch point.
Another use is to provide alternative mono or stereo output facilities on some guitars and electronic organs. This is achieved by using two mono jacks, one for left channel and one for right, and wiring the NC contact on the right channel jack to connect the two connector tips together when the right channel output is not in use. This then mixes the signals so that the left channel jack doubles as a mono output.
Where a 3.5 mm or 2.5 mm jack is used as a DC power inlet connector, a switch contact may be used to disconnect an internal battery whenever an external power supply is connected, to prevent incorrect recharging of the battery. On some DI units and guitar effects units, a normally open switch contact on one of the signal connectors is used to connect an internal battery whenever a cord is connected. The desired effect is to switch the unit off whenever the cord is removed. A side effect is to discharge the battery if it is not removed, for example if equipment is left connected overnight.
If it is desired to activate the switch contacts without actually inserting a plug in a 1/4 inch jack socket, a rod of the construction toy K'NEX can be used. However care should be taken to use a rod long enough that it can be pulled back out.
[edit] Tip Ring Sleeve
Tip Ring Sleeve (TRS) connectors are three-conductor jack plugs and the corresponding sockets, used in many stereophonic and other audio applications.
[edit] Terminology
The term is associated with telephone usage. In twisted pair wiring to this day, the non-inverting and/or "live" wire of each pair is known as the ring, while the inverting and/or "earthy" wire is known as the tip. If the pair is shielded, or if the pair is accompanied by a dedicated earth wire, this third conductor is known as the sleeve. This usage corresponds to the connection to a three-connector jack plug in a manual telephone exchange. This appears to have originated with the use of TRS jacks by switchboard operators with the tip and ring wires attached to the corresponding parts of the jack. Originally, the hot and ground were reversed, but often the metallic desktops of the switch boards were scarred by the discharge from the tips and the system was reversed to the present usage.
The term tip ring sleeve is more common in some English-speaking countries than others. Outside of the USA the term stereo jack plug is probably more common, even for connectors not used for stereo. The modern profile three-conductor jack plug was originally designed for stereo signal connections, with left channel on the tip, right on the ring and common return on the body or sleeve. The term TRS is particularly appropriate to distinguish these three-conductor (stereo) plugs used in other than stereo applications.
2. Ring: Right-hand channel for stereo signals, negative phase for balanced mono signals, power supply for power-requiring mono signal sources
3. Tip: Left-hand channel for stereo signals, positive phase for balanced mono signals, signal line for unbalanced mono signals
4. Insulating rings
| Unbalanced | Balanced | Stereo | |
|---|---|---|---|
| Tip | Signal | Positive/"Hot" | Left channel |
| Ring | Not present | Negative/"Cold" | Right channel |
| Sleeve | Ground/Return | Ground | Ground |
[edit] Usage
[edit] Audio
When a TRS is used to make a balanced connection, the two active conductors are both used for a monaural signal. The ring, used for the right channel in stereo systems, is used instead for the inverting input. This is a common use in small audio mixing desks, where space is a premium and they offer a more compact alternative to XLR connectors. Another advantage offered by TRS connectors used for balanced microphone inputs is that a standard unbalanced signal lead using a mono jack plug can simply be plugged into such as input. The ring (right channel) contact then makes contact with the plug body, correctly grounding the inverting input.
The disadvantage of using TRS jacks for balanced audio connections is that the ground mates last and the socket grounds the plug tip and ring when inserting or pulling out the plug. This causes bursts of hum, cracks and pops and may stress some outputs as they will be short circuited briefly, or longer if the plug is left half in. Professional audio equipment uses XLR connectors which mate the ground signal on pin 1 first.
TRS connectors are also commonly used as audio patch points (or insert points, or simply inserts), with the output on the tip (left channel) and the input on the ring (right channel). This is often expressed as "tip send, ring return." One advantage of this system is that the switch contact in the panel socket, originally designed for other purposes, can be used to make the circuit when the patch point is not in use. Another is that if the patch point is used as an output only, use of a mono jack plug correctly grounds the input. Use of 6.5 mm TRS connectors in this way is seen in almost all professional and semi-professional audio mixing desks.
In some, the concept is extended by using specially designed TRS jacks that will accept a mono jack plug partly inserted ("to the first click") and will then reliably connect the tip to the signal path without breaking it. Most standard TRS jacks can also be used in this way with varying success, but neither the switch contact nor the tip contact can be relied upon.
At one stage some mixing desk manufacturers, notably Soundcraft, standardized on the opposite configuration for patch points/inserts: output on the ring, input on the tip. This allowed for the insert jack to serve as a standard-wired mono line input that would bypass the mic preamp (and likely a resistive pad, as well as other circuitry, depending on the design), and thus improve sound quality. However tip send has become the generally accepted standard; Soundcraft changed their practice in the early-to-mid 1990s.
In some very compact equipment, 3.5 mm TRS jacks are used as patch points.
Some sound recording devices use a TRS as a mono microphone input, using the tip as the signal path and the ring to connect a standby switch on the microphone.
[edit] Computer sound
Personal computer sound cards from Creative Labs, Sound Blaster or compatible to these use a 3.5 mm TRS as a mono microphone input, and deliver a 5 V polarising voltage on the ring to power electret microphones from the card manufacturer. Sometimes called phantom power, this is not a suitable power source for microphones designed for true phantom power and is better called bias voltage. Compatibility between different manufacturers is unreliable.
Normally, 3.5mm 3-conductor sockets are used in computer soundcards for stereo output. Thus, for a soundcard with 5.1 output, there will be 3 sockets to accommodate 6 channels - front left & right, rear left & right, and center & subwoofer. But the 6.1 and 7.1 channel soundcards from Creative Labs are equipped with 1 and 2 sockets of 3.5mm 4-conductor sockets respectively. This is to accommodate rear-center (6.1) or side left & right (7.1) channels without additional sockets on the sound card. But speaker have normal 3-conductor sockets. In Creative's documentation, the word "pole" is used instead of "conductor".
The Apple PlainTalk microphone jack used on some Macintosh systems is designed to accept an extended 3.5mm TRS; in this case, the tip carries power for a preamplifier inside the microphone. If a PlainTalk-compatible microphone is not available, the jack can accept a line-level sound input, though it cannot accept a standard microphone without a preamp.
Plug-in power ( from: http://www.epanorama.net/circuits/microphone_powering.html )
[edit] Recording equipment
Many small video cameras, laptops, Minidisc recoders and other consumer devices use a 3.5 mm microphone connector for attaching a (mono/stereo) microphone to the system. These fall into three categories:
- Devices (usually of the "toy" variety), which use a un-powered microphone: usually a cheap dynamic or piezo microphone. The microphone generates its own voltage, and does not require power.
- Devices (usually very expensive recorders, for hi-fi or broadcast use) which use a self-powered microphone: usually an expensive dynamic microphone with internal battery-powered amplifier.
- Devices (most consumer equipment) which use a "plug-in powered" microphone: an electret microphone containing an internal FET amplifier. These provide a good quality signal, in a very small microphone. However, the internal FET requires a DC power supply, which is provided as a bias voltage.
Plug-in power is supplied on the same line as the audio signal, using an RC filter. The DC bias voltage supplies the FET amplifier (at a low current), while the capacitor decouples the DC supply from the AC input to the recorder. Typically, V=1.5 V, R=1 kΩ, C=47 µF.
If a recorder provides plug-in power, and the microphone does not need it, everything will usually work ok, although the sound quality may be lower than expected. In the converse case (recorder provides no power; microphone requires power), no sound will be recorded. Neither misconfiguration will damage consumer hardware, but it could destroy a broadcast-type microphone.
[edit] Amateur Radio / Two-Way Radio Programming
This particular type of jack is also used in the Icom IC-91AD for connecting to the Data Port allowing for either programming of the radios configuration information or connection of a GPS Receiver to the HT.
The IC-91AD uses a x.ymm version of this TRS Jack with a DB-9 on the other end. Wiring diagrams will be posted soon.
[edit] Configurations and schematic symbols
These examples are meant to illustrate each possible component of such jacks, but many other configurations using these basic components are available.
A. A simple two-conductor jack. The connection to the sleeve is the rectangle towards the right, and the connection to the tip is the line with the notch. Wiring connections are illustrated as white circles.
B. A three-conductor, or TRS, jack. The upper connector is the tip, as it is farther away from the sleeve. The sleeve is shown connected directly to the chassis, a very common configuration. This is the typical configuration for a balanced connection. Some jacks have metal mounting connections (which would make this connection) and some have plastic, to isolate the sleeve from the chassis, and provide a separate sleeve connection point, as in A.
C. This three-conductor jack has two isolated SPDT switches. They are activated by a plug going into the jack, which disconnects one throw and connects the other. The white arrowheads indicate a mechanical connection, while the black arrowheads indicate an electrical connection. This would be useful for a device that turns on when a plug is inserted, and off otherwise, with the power routed through the switches.
D. This three-conductor jack has two normally closed switches connected to the contacts themselves. This would be useful for a patch point, for instance, or for allowing another signal to feed the line until a plug is inserted. The switches open when a plug is inserted.
[edit] See also
| Audio and video connectors |
|---|
| Single conductor: Binding post | Banana plug | Fahnestock clip |
| Audio: RCA | Jack plug | XLR | DIN / Mini-DIN | BNC | DB25 | Speakon | TosLink |
| Video: DVI / Mini-DVI / UDI | RCA | VGA / Mini-VGA | DFP | P&D | BNC | DIN / Mini-DIN | 13W3 | D4 | DisplayPort |
| Multi: ADC | HDMI | TRS | SCART | F | Belling-Lee | DisplayPort |
