1/4 inch mono jack 3 pins

[RaymondM.]

This component is a mono jack but it has 3 pins. Can somebody please tell me what the purpose of the third pin. My knowledge of electronics is limited but from what I understand a mono phone plug has a tip and a sleeve, the tip is the signal and the sleeve is the ground but this jack has a third pin. Somebody else from Amazon told me that the first pin behind the jack hole is the ground but he didn't tell me which of the other two pins is the one I solder the signal to. There are a bunch of sellers on Ebay who carry this item but I can't get an answer from them either. Searching the web for pictures of schematic diagrams didn't reveal an answer, only pictures of panel mount jacks. Those have two pins. Clear as day which is which. But no diagrams of a pcb mount jacks like in my picture.

 

[Hopup]

Look at the datasheet for all the necessary information.

 

[RaymondM.]

Thanks for the reply which reminded me...There is no data sheet available, at least none that I can find. Other people who bought this component on Amazon have noted the absence of a data sheet as well. I bought mine from AliExpress. You can buy a bag of them for a couple of bucks and free shipping. The seller didn't have a data sheet.

 

[Hopup]

In that case you could plug connector with wire in one of the mono jacks and use multimeter.

 

[Harald Kapp]

It's possibly a mono jack with a built-in switch. When no plug is inserted, a spring contact is closed to allow current flow. When a plug is inserted, the spring contact is opened and current flows through the plug. You'll have to find the exact configuration of your jack by measurement.

Read here for more information.

 

[RaymondM.]

Thanks for your replies. I'm guessing when you say "measurement" this means a continuity check? That sounds good.

 

[BobK]

It's possibly a mono jack with a built-in switch.

Or a stereo jack.

Bob

 

[Audioguru]

When you buy cheap Chinese junk from Amazon, ebay or AliExpress then you usually receive cheap junk with no information about it. A Name-Brand part made by a real manufacturer will have a long lifetime and has a detailed datasheet.

 

[shrtrnd]

If anybody's taking a vote, here's my vote:
If you're SURE it's not a STEREO jack as offered by BobK, (I assume you know Mono (2-lead) vs Stereo (3-lead).
I'd tend to believe Harald Kapp's theory of a switched jack. Designed to send the audio signal to an amplifier, but when you plug in the headphone, an internal leaf spring disconnects the signal connection to the amplifier, and re-routes it to the headphone plug.
If you have a continuity checker, you can easily verify what you have.
Just as trivia, the only other time I've seen a mono jack in the housing you've shown in the pictures that wasn't actually a signal connection: the third lead was just molded into the housing for jack stability on the PCB.
Helps relieve some of the stress associated with inserting and removing the plug so the jack doesn't come loose
and break off (But THAT third pin was for mechanical purposes, and had no electrical connection to it).

 

[RaymondM.]

If anybody's taking a vote, here's my vote:
If you're SURE it's not a STEREO jack as offered by BobK, (I assume you know Mono (2-lead) vs Stereo (3-lead).
I'd tend to believe Harald Kapp's theory of a switched jack. Designed to send the audio signal to an amplifier, but when you plug in the headphone, an internal leaf spring disconnects the signal connection to the amplifier, and re-routes it to the headphone plug.
If you have a continuity checker, you can easily verify what you have.
Just as trivia, the only other time I've seen a mono jack in the housing you've shown in the pictures that wasn't actually a signal connection: the third lead was just molded into the housing for jack stability on the PCB.
Helps relieve some of the stress associated with inserting and removing the plug so the jack doesn't come loose
and break off (But THAT third pin was for mechanical purposes, and had no electrical connection to it).

Thanks. This is very informative. The description of the item was "Mono". That's what was confusing to me, the third pin. A switched jack or an extra pin for stability. Any advise on how to use the continuity checker to determine which it is?

 

[RaymondM.]

When you buy cheap Chinese junk from Amazon, ebay or AliExpress then you usually receive cheap junk with no information about it. A Name-Brand part made by a real manufacturer will have a long lifetime and has a detailed datasheet.

Lol. Just about Everything is made in China, even the brand name stuff. China even makes some components for our missiles. But at least you get a data sheet with your component when you buy from Switchcraft or whoever.

 

[Robert_fay]

This is not your switch, however easy to test. Continuity between the two post with no plug installed and open with plug installed or open then closed.

 

[RaymondM.]

Thanks Robert. Now I know which pin to solder the ground and signal from my project. Much appreciated. AND, it appears that this jack I have as a stereo and not a mono as described in the listing because when I put a stereo plug in both pins sound continuity. With a mono plug, just one pin. So, I guess you can't believe everything you read. It caused me confusion because a picture of a mono jack only had two pins (Radio Shack) and not three like mine.

 

[(*steve*)]

A mono signal from a microphone may use 3 leads. If the signal is balanced then there are two outputs with opposite phase and a shield.

The idea is that him is likely to be a common mode signal with respect to the shield, and that it will be largely rejected by a differential amplifier.

In this application it is not unusual to see stereo plugs used for mono signals.

However if it is indeed a socket which allows for only 2 electrical connections to the plug, then the likely options are that it is a switch contact (as mentioned above) or an additional connection point which provides mechanical stability. In the former case the continuity between some of the pins of the difference will change as a plug is inserted, in the latter it will remain regardless.

 

[RaymondM.]

Okayyyyy...(signifying growing perplexity)
With no plug the meter indicates no continuity between the ground pin and either of the two rearward pins. That makes sense to even a newb like me. Inserting a stereo plug the meter sounds off when either of the rearward pins are touched, along with the ground pin. Inserting a mono plug only one of the rearward pins sound off. The other remains silent. Does this mean that this "mono" labeled jack is actually a stereo jack or a switched jack? Doing a web search on a switched jack didn't reveal anything that I could understand. What IS the purpose of a switched mono jack? I know it's supposed to turn something on or off but what is it commonly used for in a mono jack to turn what on and off. Thanks for your input.

 

[BobK]

I cannot make sense of your tests. I don't see how inserting a stereo plug could short more of the pins together than inserting a mono plug.

When you insert a mono plug, it sounds like it is a switched plug that shorts the extra pin to ground when a plug is inserted, But inserting a stereo plug should either do the same or not short anything at all depending on where the contact is. How a stereo plug shorts all three pins together is beyond me.

Bob

 

[RaymondM.]

I cannot make sense of your tests. I don't see how inserting a stereo plug could short more of the pins together than inserting a mono plug.

When you insert a mono plug, it sounds like it is a switched plug that shorts the extra pin to ground when a plug is inserted, But inserting a stereo plug should either do the same or not short anything at all depending on where the contact is. How a stereo plug shorts all three pins together is beyond me.

Bob

You don't understand what I'm saying? I read it over again and it sounds like gobbledy gook to me too. So, I just went to online Radio Shack and bought a 1/4 inch mono jack with just TWO pins, one for ground and one for the signal. End of problem.

 

[KJ6EAD]

It might be helpful to start using some standard terminology in this discussion.

https://en.m.wikipedia.org/wiki/Phone_connector_(audio)

 

[(*steve*)]

I shudder when I see someone use the term "jack" because I have to try to read in context whether they mean the plug or the socket.

I know "jack" has a specific variable meaning (!) and I prefer not to jack people up by dropping jack into a conversation with some jack-of-all-trades who doesn't knows jack about the difference between a jack, a jack plug, and sometimes even a car jack.

In a similar note, is a plug male and a socket female? And if the male connector is changed for an RP version, is it now female (and if so, is it a socket), or is it better described as bisexual or transgender, or maybe just "gender challenged"?

 

[RaymondM.]

I apologize if I'm not using what you folks consider "standard" terminology. Perhaps you might direct me to to a dictionary of electronic component terminology accepted by this forum. My use of "1/4 inch mono jack" in a search returned results from all over the Web: Amazon, Ebay, Wikipedia, BG Micro Electronics, All Electronics, Switchcraft etc.,etc.. But hey, I'm just a guy who has no experience in this area, other than as a hobbyist 35 years ago, who recently saw a clever idea (guitar sustainer) and thought I'd give it a try building it because the commercial product is ridiculously overpriced, legacy technology. Again, sorry if I confused you. I'm a little confused myself at the moment.