# Understanding Audio Jack Connection

I have circuit that has an audio connector that has the following diagram.

Audio connector is one that I am not familiar with. What I gather is that the rectangle on the left is the sleeve (entry point).

The tip    is pin 2.
The ring   is pin 3.
The sleeve is pin 1.


Is this correct or did I misunderstand how to read this symbol ?

Added:

Link to product page

Datasheet

• Do you have datasheet for the part? – Tom Carpenter Oct 28 '17 at 20:23
• Typically the box will be the sleeve and will usually have a connection coming from it. Pin 1 may be the second ring in a TRRS jack. – Tom Carpenter Oct 28 '17 at 20:25
• @TomCarpenter Added product page and datasheet. – efox29 Oct 28 '17 at 20:29
• As a bonus, with a generic stereo audio connection, you should remember the 'three Rs' which are Red Right Ring, the right channel is on the ring of a TRS, and uses the red wire. With a mic connection, there are several standards, check! – Neil_UK Oct 29 '17 at 5:37

## 2 Answers

TL;DR; You are correct in your determination of how the contacts will make connections to a TRS jack (see diagram below).

Based on the datasheet, the jack is indeed designed for 3-pole TRS jacks. However on examination we can see that the shell of the connector is plastic. We can also deduce from the measurements that the contact for pin 1 is not technically the sleeve contact.

Instead pin 1 is equivalent to the second ring contact on a 4-pole TRRS socket. This explains why in the connector symbol they show pin 1 connected as a third arrow as opposed to a wire joining to the sleeve (the rectangle). From the diagram below of a TRRS jack, each of the arrows on the symbol corresponds to one of the Tip, Ring 1, and Ring 2. The box corresponds to the sleeve.

If we examine the difference between the various types of jack (specifically TRS and TRRS ones), it can be seen that the connector will still work fine for a TRS jack. This is because the contact at the second ring position will in fact contact the sleeve on the TRS jack.

Note:

This type of connector could be used fine in audio for headphones that use a TRS jack - i.e. just headphones, and no microphone.

The connector could also be used with TRRS jacks using the AHJ or CTIA standard where the ground is located at the second ring.

You could not use this connector for TRRS jacks wired for the OMTP standard where the ground connection is the sleeve, because pin 1 would not make contact.

• I checked the datasheet. There is no solder pin for the TRRS sleeve on the datasheet drawing. It's very unclear. My answer is a muddle now! – Transistor Oct 28 '17 at 21:23
• I was just about to write - even asking simple questions, you can learn alot! But now I'm all over the place because everyone else is over the place. But this is still good information (for me at least). – efox29 Oct 28 '17 at 21:24
• @efox29 I think the simplest thing is to look at the diagram in the answer. It should make it clear how the connections will form when using that connector. – Tom Carpenter Oct 28 '17 at 21:25
• Understood. The diagram helped understand but also the additional tidbits of information. – efox29 Oct 28 '17 at 21:27
• Interestingly, if you compare the picture to the 1503 13, you can see that the 4-pole version has a metal tab just inside the opening of the connector which forms the TRRS sleeve contact, whereas the 3-pole version doesn't have that metal tab. – Tom Carpenter Oct 28 '17 at 21:36

"The great thing about standards is that there are so many to choose from!"

Your diagnosis may not be correct.

Figure 1. Standard 3.5 mm jack pinouts. Source: Prohardver.

... for a four-pin version you might use the rectangle as a fourth pin.

The four-pin plugs are known as TRRS (tip, ring, ring, sleeve) and the pins named as T, R1, R2 and S.

Update after datasheet link added.

The datasheet states that it's a 3-pole stereo jack socket - for the first plug in Figure 1.

Figure 2. Photo of the socket from the product page. Note that the sleeve contact forms a strap across the socket holding it firmly to the PCB. There are two terminals marked '2'. See Figure 3.

Figure 2. PCB pinout from datasheet.

The datasheet shows that two is connected twice and that it's closest to the connector entry point. Again, your interpretation is correct.

Figure 4. The rectangle is probably a hangover from the days of the open-jack. These are commonly found on guitars and amplifiers. The pin contact diagram is incorrect in that case as it shows pin 2 furthest from the jack entry point.

The circled region in Figure 4 was the contact for the sleeve. It appears that the modern diagrams are leaving the rectangle there but not showing a connection to it as the barrel is plastic.

The diagrams are not clear. I think you need to test it when you receive the part!

• The rectangle symbol would indicate a connection though right ? Or is it known that the rectangle always has a connection ? – efox29 Oct 28 '17 at 20:35
• From the picture on the datasheet, the body of the jack,, including the entry hole, is plastic, so there would be no "automatic" connection to the plug sleeve, so contact 1 was added to make contact with the sleeve. If the rectangle was metal, and used as a connection, it should have a line going to the right, and a terminal number. – Peter Bennett Oct 28 '17 at 20:47
• See Figure 3, etc. – Transistor Oct 28 '17 at 20:48
• By the diagrams of dimensions and the picture, it is effectively a 4-pole socket with the sleeve removed. Pin 1 would still make contact with the sleeve of a standard 3-pole TRS jack. However for a TRRS jack it would contact the second ring, not the sleeve. Hence I the choice of symbol. – Tom Carpenter Oct 28 '17 at 21:03
• Man, I'm all mixed up. My mind was somewhere else. I'll sort it out in a while. – Transistor Oct 28 '17 at 21:05