In Praise of the Quarter-Inch Phone Jack

I am blessed/cursed with a mind that tend to see things a bit differently. A good friend of mine who is a famous rock journalist (Hi Alan!) says that he can always count on me for an alternative, usually contrarian viewpoint. One of the ways my contrarian-ism manifests itself is with a fascination with things that many others find trivial or dull, musicologically speaking.

Like the ¼ inch phone jack:

The humble 1/4 inch phone jack; often seen, never thought about.

Connecting cables using the ¼ inch phone jack are ubiquitous; if you have ever seen any type of electrified music performed live, you've seen one. If you've plugged an electric guitar/electric bass, electric keyboard or anything else into an amplifier, you've used a quarter-inch phone jack cable. Pretty much every music store I've ever been in, except for those that specialise in antique instruments, sell them. Even if an electric guitar player is playing wirelessly, the transmitter still is connected to the guitar, and the receiver is connected to the amplifier, by ¼ inch jacks.

The design and nomenclature of the ¼ inch phone is mostly self-explanatory; “quarter inch” is the diameter (roughly) of the business end of the male connector and the hole it fits into. The term “¼ inch” is typically used the to differentiate the quarter-inch phone jack from other similar connectors of different sizes, such as the mini phone plug. “Phone” refers to the fact that these connectors were originally designed to connect phone calls on old-fashioned manual telephone switchboards. The term “jack” is a little bit more obscure; one of the early types of electrical switches was the bladed throw switch, in which a hinged metal blade with a handle at the end would complete an electrical circuit when pushed into a metal receiving clip. If you have seen old Frankenstein movies, you have seen the good doctor use these at the dramatic moment when he brings his monster to life (although in this case, they are double throw switches with a single handle). The old name for these switches was “jack-knife switch”, since the pivoting blade resembled the blade on a jack-knife. From there, temporary electrical connectors of any sort became known as “jacks”. The proper old-school name for the ¼ inch phone jack is TS (Tip, Sleeve) connector; the tip of the jack is the contact point for the hot (positive) lead, while the sleeve and casing is the (negative) ground. Stereo quarter inch phone jacks – typically used for stereo headphones – are known as TRS (Tip, Ring, Sleeve) connectors; a ring on the shaft of the jack between the tip and the sleeve is the contact for the second hot lead, allowing a stereo connection.

Phone jacks were invented in the late 19^th century and changed little since then. The most commonly known variety of ¼ inch phone jack is the one designed and marketed by the Switchcraft company in 1946 (shown above). Considering how ubiquitous they are as musical connectors today, it’s strange to consider that phone jacks were just one of many options available for connecting nascent electronic musical devices to amplifiers. The 1929 Stromberg-Voisinet Electro guitar and its associated variants (the first amplified instruments with a pickup to be marketed) used so-called “banana plug” connectors – which are smaller and somewhat less robust than phone plugs, as well as being generally un-banana like – in which each end of the connecting cable ended in two individual plugs, one for hot and one for ground. Lloyd Loar’s ViViTone instruments of the mid 1930s also use these connectors. The wood-bodied prototype of the Rickenbacker frying pan – the first electric guitar – used a screw-down bare-wire connector, of the type that radio hobbyists often employed. However, the aluminium-bodied production version of the Rickenbacker frying pan used quarter inch phone jacks up to connect the instrument to the amplifier. And with very few exceptions (Russian electric guitars made during the Soviet era used a five wire jack similar to a modern 7 pin MIDI connector – possibly to assure non-compatibility with western instruments), every electric guitar, everywhere, since that time has done the same.

Yet there is no particular reason that this should be – there are lots of ways of connecting electronic wires to electronic devices and few modern electronic devices use the same connectors they did in the 1930s. Yet for instrument-to-amplifier connections, the quarter inch phone jack has reigned supreme since 1932. If it seems not strange to you that it is possible to plug an electric guitar from 1932 into an amplifier made over 80 years later, consider the difficulties you would have in trying to charge your mobile phone with any other charger other than that provided by the manufacturer, in spite of the fact that all phone-chargers essentially function in the same way; Apple, for example, seems to make non-inter-functionality of its iPhone accessories inherent in the design. And speaking of power supplies, even mains-power (plug-into-the-wall type for my American readers) has changed greatly over the past 80 years in both the United States and United Kingdom. The US has gone from a two-pin socket (which back in the day would allow certain types of two-pin plugs to be connected in such a way as to reverse the electric device's polarity – which sometimes had dangerous results) to the modern three-pin grounded-type. Although uncommon now, you can still sometimes see the obsolete two-pin type in older houses. Up until the late 1960s, the UK had several competing electrical connection systems; it was common for electrical appliances to actually be sold without the wall plugs – after you purchased your device, you would then have to install the correct plug for use in your house. (A slight digression here, I have seen some of these older-type sockets in homes built in the 1920s and 30s, and for some reason, the sockets are located at waist height, rather than near the floor. The light switches in these houses were also mounted at the same height, which seems rather low to modern eyes.)

And the ¼ inch phone jack wasn’t just the standard for connecting instruments to amplifiers; synthesizers of the 1960s and 70s which used a patch bay-type system to enable signal circuitry (modern modular analog synthesizers use the same system), use these quarter-inch cables in a manner very reminiscent of their original function: directing signals in a telephone switchboard. However, it's not clear if their 1960s and 70s use was due to the telephone switchboard connection or the quarter-inch jack's by-then ubiquity in electric music.

Now I understand my obsession with quarter-inch phone jack cables may be a little strange. As an undergraduate I composed an art-music piece for six amplified quarter-inch phone jack cables; the musicians played the cables by touching the live tips of the phone jacks, producing the buzzing 50 cycle hum (which would be 60 cycle hum in the US) that’s familiar to any musician who was plugged something into an amplifier. By judiciously selecting the amplifiers used for the performance by the quality of their earthing ("grounding" in the US), it was possible to create a quite varied sound-world.

So why, has the quarter-inch phone jack remained the go-to connector for electric musical instruments for over 80 years? There are actually two ways to answer that question. The first is with reasons; phone jacks were easily available, they were robust, and they did the job in a simple and elegant fashion. There was no need to invent something else. The second reason is… no reason at all; they probably remain the standard, not because of a conscious decision made by a person or organisation, but the lack of a decision to change to something else – since it worked, no one thought about it, so there was no reason to change it. Although common and unpretentious, the quarter-inch phone jack still bears thinking about; it’s hard to overstate how vital ¼ inch phone jacks are as tools of the contemporary musician.

If electricity is the blood that drives modern music, quarter-inch phone jack cables are the veins that keep that music flowing.