Normally-Closed 3.5mm jack acts incorrectly

Hi! So, I just bought myself 6 Normally-Closed 3.5mm jacks and they seem to have a bit of an issue on my PC: they reverse the connected/disconnected functionality (when I physically connect headphones, they show up in Windows as disconnected and when I physically disconnect them, they show up as connected).

Now, all my cases have 3.5mm jacks that correctly work with my PC, so they are alright.

What can be the cause of this issue? All my cases (3 cases) have Normally-Open jacks or could I have soldered the jack wrong?

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In your post

You mention NC and NO jacks. NC, NO = normally closed and normally open.

Since these are opposite in their effect and your complaint is they are opposite as to Windows, maybe you need the NO jacks in this system.

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Well, probably

But this just blows my mind: it's standard for the 3.5mm jacks to be NC. Since when have we been using NO jacks on our cases? Because my Front Panel PCB is only connecting the pins from the HD AUDIO plug to the jack.

So, if I need NO jacks, it's because most SoundCards (integrated and dedicated) are designed to work with NO jacks? But the standard is NC?

If this is the case, I have no idea where I could find these NO jacks in Europe.

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I haven't seen a schematic on this area

In years. But your symptom does tell us a story. As to the EU I'm not good on sources. Here in the USA we have Amazon and other parts supply outlets (Radio Shack is long gone.)

We have Mouser in the USA and I see they are in the EU at

You can test if this is needed by adding a switch to your wiring as a test. I take it you are an electronics tech due to what you wrote so far or better.

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PS. It appears there are other ideas on this.
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That link is for Realtek sound systems

I have a Soundblaster Audigy FX, which automatically switches the audio output to the front audio when available. So, I really don't think I can fix it in the drivers. This is for sure going to need some circuitry done to it to reverse that switch behaviour. If you have any idea regarding a circuit that reverses the behaviour, it would be welcome.

Also, that link you sent me only fixes an annoyance on Realtek HD Audio software.

I got these 3.5mm jacks from I have seen that Mouser site, but it seems like it has less products that TME.

I am not an electronics tech, I just deal with electronics as a passion.

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We can do that.

You'll have to take off the wire that is going to the switch and connect it to a relay. Since my bet is +5V is available on the sound board, USB and more then think about this switch in that jack that in 99.99% of the systems connects to ground when NO or NC.


The jack's switch is ground or not. ANY jack's switch now goes to a relay GROUND power pin and the other relay power pin goes to USB +5V or similar.

Now this relay will change state as you plug and unplug your jack.

We're halfway done.

Relays are available with SPDT so we can put ground on the relay center pin and the NC or NO pin goes to the sound card.

Relays that look suitable are at

Post was last edited on September 23, 2019 12:04 AM PDT

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What you're saying is I should disconnect the pins that make the switch in the 3.5mm jack and connect one of them to a relay. To the relay I also have to connect 5V DC.

I have two questions: is this relay good? I would prefer to aquire a relay from TME, as I have a local importer that can order from TME and not charge me delivery.
Second question: how does that relay change state when I plug the headphones in the jack?

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I can't tell what price that is.

But it is the common 5V (coil voltage) with SPDT contacts.

Second answer. Because your headphone (NO or NC DOES NOT MATTER) jack's detect switch switches from open to ground or ground to open, this provides a current return path or not to the relay coil. So now you have a relay that changes state when you plug in the headphone.

Again. The ground pin of the relay's coil goes to the detect connection of the jack (does not matter if NO or NC!)

AND the +5V of the realy's coil goes to some +5V source like USB or other place in the PC.

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Now I understand

For your answer to my first question: it's $3.84 for less than 50 pieces.

For your answer to my second question: that actually makes sense now. Thanks for explaining. As soon as I can get my hands on that relay, I'll wire it.

I checked a schematic for the pin configuration on a relay and now I have another question. A relay (the one I sent you a link to included) has 2 pins for switching: a NC one and a NO one. When should I connect the jack switch cable to the NC pin on the relay and when on the NO pin?

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As to when.

When it works OPPOSITE of how you desire you swap from NC to NO or vice versa.

I'm sorry that I didn't offer a MUCH SIMPLER SOLUTION and could be something you have laying around. Ready? (forget much of the above.)

For the sense input, run that to one side of a SPST (single pole single throw) toggle switch. The other side runs to a ground of the same area.

This won't make it automatic but is the simplest "fix" that I should have mentioned but my mind was going in how to make it automatic if you couldn't find a jack with the opposite NC/NO scheme.

This also can have another nice side effect which in some situations gives you an instant MUTE switch.

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I'll choose the first fix. A bit of documentation on my side won't hurt, as this is a domain I'd like to start learning well into. What I don't understand is which pin does what on a 5 pin relay and that's why I keep asking things. Otherwise, I somewhat understand the circuit I have to make.

Post was last edited on September 23, 2019 12:27 PM PDT

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Kudos to that!

This is a very nice entry level design to learn about relays and things you can do with them.

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After a lecture on those pin configuratons

I only now see one big issue: where can I get a safe ground connection from within my computer for the COM pin on the relay? I don't want to use the ground pin from my jack, as I need the connection between my jack and my headphones to be grounded, so what are my options for a safe ground connection?

Post was last edited on September 23, 2019 12:36 PM PDT

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Ground is ground.

You can use the ground on the audio jack for more than one use. Or you can use a ground from some USB port or on most motherboards you find the owner didn't use all the internal USB ports which gives us a way to make or use a plug for picking off the USB +5V and USB Ground. I like the USB +5V since it is current limited and avoids tapping into a PSU +5V which can be awful if you have a short circuit. USB +5V is your safe supply for DIY work.

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Grounding on unused USB would be a good solution indeed

I didn't think of that. Thanks!

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A truly simple method

That image describes all I have to do. After doing some digging up, I found out that HD AUDIO front panels use proprietary NO 3.5mm jacks and older style AC'97 use the NC 3.5mm jacks. All I have to do is rewire my HD AUDIO cable and I have audio trough the new jacks, even if the connected/disconnected functionality will be gone.

Post was last edited on October 7, 2019 7:20 AM PDT

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The simplest method.

I admit I didn't go there because the clients I've worked with on this DEMANDED it work as intended. I apologize that I didn't cover that method here.

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Normally-Closed 3.5mm jack acts incorrectly

Hey, thanks for sharing I always look forward to reading your posts one of the few blogs I still follow....

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Probably wrong thread

Look out when replying to threads, make sure you don't click on the wrong one.

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