1/4″ Phone Jacks and Plugs

by gaussmarkov

Custom gaussmarkov mojo cables kick off this post about 1/4″ phone jacks commonly used in stompboxes. 😉 This tutorial supplements a recent post on wiring up a stompbox with off-board components.

Mono and Stereo Phone Plugs


Here are two artifically coloured 1/4″ phone plugs, mono above and stereo below. The green part is called the sleeve and the red part is called the tip. The stereo plug has an additional part (silver in this figure) called the ring. The tip, ring, and sleeve are all insulated from each other and can be used for different purposes. Stereo plugs are sometimes labeled TRS, the initials of Tip, Ring, and Sleeve.

Guitar cables generally have mono plugs where the tip carries the audio signal and the sleeve connects to ground. Stereo plugs appear on headphone cables. If you put a mono plug into a stereo headphone jack, the silver part is replaced by the grounded sleeve and one channel is grounded and, hence, silent. Because the Ring usually carries the Right channel, the right channel is typically silenced.

Mono, Stereo, and NC Jacks


These colourful images represent three panel mount Switchcraft jacks:

  • mono (Switchcraft no. 11 on the left),
  • stereo (Switchcraft no. 12B in the middle), and
  • mono with NC (or normally closed) switch (Switchcraft 12A on the right).

Following the colour scheme above, I have made the sleeve connection green and the tip connection red.

The role of the silver part in this figure depends on the jack. For the (middle) stereo jack, the ring connection is silver. For the (right-hand) mono with NC switch, the shunt for the switch is silver.

Each part of the jack has a solder lug where wires are usually connected. The tip lug is not always located in the same place. Other manufacturers than Switchcraft may use a completely different configuration of the solder lugs for each of these jacks. You can use the contintuity test of your DMM to figure out which lug goes with each plug connector. Alternatively, you can figure this out visually.

Jack Layers

These jacks are constructed in layers, with a single piece of metal comprising the lugs and the plug connectors. I have never taken one apart, but there must be some sort of insulation that separates these metal layers from the barrel that contacts the sleeve. So you can just look from the side and see which lugs and connectors are paired.

Jack Schematic Symbols

Schematic symbols for these three jacks often look like these. Layout symbols are similar.

Mono, Stereo, and NC Jacks


Often mono plugs are mated to mono jacks and stereo plugs are mated to stereo jacks as shown above. Notice the position of the tip connection. The “click” that you feel when you plug into your guitar, stompbox, or amp is the (red) metal tab that contacts the tip snapping into the groove around the tip. This holds the plug firmly in place until you pull it out. After repeated use, jacks must be replaced when metal fatigue occurs and the jack no longer grips the tip tightly.

Also, compare the mono and stereo arrangements and you will see how a separate connection is made by the ring of the stereo plug touching only the silver metal tab of the stereo jack. Below we will discuss a case where such a separate connection is not desired.

When inserting a 1/4″ phone plug into these jacks, the tip first contacts the grounded socket before reaching the tip connection at the end of its travel. The sleeve connection comes later. This initial contact between tip and ground without a grounded sleeve causes the pops and hum one hears as a cable connected to an on-line amp is plugged into a guitar.

Mono, Stereo, and NC Jacks

The figure above shows how the mono jack with NC switch has a tip connection that is closed without a plug and open when a plug is inserted. This is useful in stompboxes like Sean MacLennan’s B Blender. His circuit provides an “effects loop” that is blended with the input signal. By using mono jacks with NC switches for the effects loop, a default connection is possible through the shunt lugs when nothing is plugged into the loop jacks.

Mono, Stereo, and NC Jacks

This figure illustrates how a stereo jack is used as the input jack for a stompbox to switch the ground connection of a battery. The plug is, of course, a mono plug. The ring part of the jack touches the sleeve of the mono plug. If the sleeve part of the jack is grounded as usual, then the mono plug grounds the ring connection. Without a plug, the ring connection is floating.

So the battery’s negative terminal is wired to the ring solder lug of the stereo jack. When there is a mono plug in the jack, the negative battery terminal is grounded and electrons flow. Without the plug, the ground connection is broken. In this way, the battery is disconnected whenever the stompbox is not in use.

Other Jacks

There are more elaborate jacks than these three. There are jacks with more rings, with more NC switches, and also with NO (normally open) switches. For examples, see the Switchcraft link listed below. Although these exotic jacks do not usually find their way into stompboxes, you will certainly encounter them in guitar amplifiers.

The illustrations above picture “open frame” metal jacks.  There are also panel mount jacks that enclose the plug connections inside a plastic box. For example, see these Switchcraft jacks.  Such jacks are often used to insulate the sleeve connection from the enclosure. This can also be accomplished with open frame metal jacks using nylon washers.

PCB mount jacks offer another possibility. These are also enclosed and quite compact. For an example of their application, see the design described in A Nice Design for 1590B Enclosures.

References and Additional Resources

  1. Neutrik Jacks
  2. Switchcraft Phone Jacks
  3. Wikipedia: TRS Connector

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24 Responses to “1/4″ Phone Jacks and Plugs”

  1. gaussmarkov: diy fx » Wiring Up a 1590B said:

    […] 12B. The output jack is a mono Switchcraft called the 11. You can read a post about these jacks in 1/4″ Phone Jacks and Plugs. The switch is a 3PDT Taiwan Blue. The picture […]

    Posted 02.06.2008 at 7:02 pm

  2. suprleed said:

    Whatever you used to render the graphics in this article is awesome! Great work.

    Love your website, I refer to it constantly.

    Posted 09.06.2008 at 10:59 am

  3. gaussmarkov said:

    the 3d software i used is called POV-Ray. you can get it at http://povray.org/.

    and thanks for the feedback. i’m pleased, of course, to hear that this website is useful. 😎

    Posted 10.06.2008 at 5:29 am

  4. Anonymous said:

    thanks for the diagrams greatly appreciated as there is no other site that simplifys these schematics so well.

    Posted 02.03.2009 at 12:24 am

  5. cesar said:

    gaussmarkov can please include the code in the povray of yours images to fit eagle3d
    thank you very much

    Posted 17.03.2009 at 8:04 am

  6. Red Eagle said:

    Finally, a simple genius. Thanks for creating a foolproof scenario for wiring, Be well, Red.

    Posted 21.05.2009 at 3:09 pm

  7. Brian Lemin said:

    I am electronically ignorant. Your diagrams have been a great help. Many thanks.

    I go to a shop and ask for a component and take what they give me!

    The gave me a female 1/4 jack plug for my little 9v amp (CHAMP) that has 6 (!) tags on the bottom and one at the top near the input (earth I presume?) I am using a mono amp and have a mono jack.

    Can you tell me how to wire this up please?

    Posted 05.06.2009 at 8:58 pm

  8. bill cino said:

    Great illustrations! Thanks for ending my long search for clear info. I CAN USE A STEREO CORD IN A MONO PLUG !!!

    SIMPLE BEAUTY: a BARITONE UKE with all strings tuned to the same note. Can be a 100 dollar cheapo ,still sounds profoundly sweet. Slide sounds great too. Must be BARITONE!

    Posted 06.06.2009 at 10:35 am

  9. Steve said:

    Great coverage of the shunt jack! I had been reading some schematics elsewhere on the shunt type of mono jack and your diagrams proved my understanding was correct.

    Posted 23.06.2009 at 8:31 am

  10. Flavio (from Brazil) said:

    Man, you can’t imagine how I’m thankful to you for that great class. Answered all my questions about jack wiring at once for all
    Thank you very much!

    Posted 02.10.2009 at 1:28 am

  11. Rob said:

    I have inadvertantly bought some mono jacks with nc switch, and have been confused about them for a while. There isn’t much info on them on the web, so thank you for explaining them so well with great graphics.

    Posted 17.11.2009 at 10:13 pm

  12. gaussmarkov said:

    everyone: cool. it’s a pleasure!

    Posted 18.11.2009 at 1:02 pm

  13. walker said:

    Thanks for this Paul! I spent weeks trying to debug my homemade ‘beavisboard’/breakout box’. I stumbled on your site and I love these graphics! They are completely idiot proof, which is great because I’m a complete idiot. : )

    It turned out I mixed up the tip and sleeves in my box. Now I’ve got that working, and put a few successful circuits on the breadboard. Thanks again!

    Posted 24.02.2010 at 12:38 am

  14. Ed Moore II said:

    I searched all over to find the pinout for a mono jack and your site is the best. All the other sites I found drove me nuts. This site made sense.

    Posted 16.04.2010 at 11:08 am

  15. Eldergeek AKA Don Crowder said:

    I want to publish the construction plans for an impedance matching patch box, for speaker cabinets, on my website and your colored phone jack would be useful. May I use it? I’ll link to this page if you like or give you credit for the image. Whichever you prefer. Thanks.

    Posted 09.05.2010 at 9:55 pm

  16. gaussmarkov said:

    Dear Don,

    Yes (thanks for asking), you are welcome to use the images. Linking the images back here would be great.

    Cheers, Paul

    Posted 14.05.2010 at 10:28 am

  17. Lionel Kaliko Fase said:

    i love this site it helped me soo much!! but im having trouble with connecting a dc power jack, im completely stumped. do you have any suggestions or links to diagrams or anything for wiring a dc power input jack?

    Posted 06.07.2010 at 12:45 am

  18. winson said:

    sorry maybe this is a stupid question but i really want to understand,
    if i use mono plugs into stereo jacks is it will spoil the guitar or my mixer?

    mono plugs => stereo jacks
    stereo plugs => mono jacks

    Posted 09.11.2010 at 6:36 am

  19. ConnectorsUSA said:

    Thanks for the great info and diagrams.

    Posted 16.11.2010 at 3:27 pm

  20. Rami939 said:

    Excellent diagrams.
    You Rock my friend !!!

    Posted 03.09.2011 at 4:14 pm

  21. Po said:

    Every time I wire up with this schematic: I find that if using an external dc source, the led will cut out if the internal battery clip (negative terminal) makes contact with the case. How can I avoid this?

    Posted 12.02.2012 at 6:54 pm

  22. Pedro said:

    Hello, I’want know if you have the Eagle cad library for switchcraft phone jacks and the neutrick jacks for instrument? And where I can foud that?


    Posted 28.03.2012 at 5:59 pm

  23. Who Calls Me said:

    I do not even know how I ended up here, but
    I thought this post was good. I do not know who you are but certainly you’re going to a famous blogger if you aren’t already 😉 Cheers!

    Posted 13.05.2012 at 11:06 am

  24. Bill said:

    How can I wire a 1 4 mono female to recharge a 6 volt battery?

    Posted 01.06.2012 at 4:59 pm