- Joined
- Jan 22, 2014
- Messages
- 373
- Motherboard
- Gigabyte GA-Z87N-WIFI
- CPU
- i7-4770
- Graphics
- MSI GTX 760 ITX
- Mac
- Classic Mac
- Mobile Phone
I was on a quest for weeks to find panel mount jacks that conformed to the Intel HD audio spec. It requires a 3.5mm (1/8") stereo jack with an isolated switch to tell the motherboard a plug has been inserted. These jacks are hard enough to find as circuit board mount, but impossible to find as threaded panel mount. Here is the typical Intel front panel HD audio circuit (Pulled from here)
After digging into the Intel HD audio spec, I found that all the jack switches do is insert a fixed resistance value between the Sense_Send pin and ground. Each jack is assigned 1 of 4 resistance values, but each manufacturer may use these values for different jacks. Here is the basic idea:
So, with this in mind, I came up with an idea to cheat and use TRRS (Tip, Ring, Ring, Sleeve) jacks that are much more common. They are available in threaded panel mount, as well as circuit board mount. The idea is, you figure out what values your mobo uses for pin 6 to ground and pin 10 to ground when no audio cables are plugged in. Unplug the front panel from the mobo, as well as any cables you might have plugged into the rear panel, just to be safe. Then you can measure the resistance with a multimeter to figure out what values to use. They should be one of the 4 values above.
Now you can use a circuit like this:
It should work because regular computer headphones/mics use TRS connectors (just one ring) and when you plug them into a TRRS jack, it will short the first ring to ground along with the sleeve. That puts the resistor into the sense_send circuit and tells the motherboard what jack is now occupied.
There is a bonus too: If you use a 4 conductor TRRS extension cable plugged into this front panel, it won't tell the mobo you have something plugged in until you plug into the far end of the extension cable. This allows you to have a remote headphone jack!
The down side is you can't plug TRRS earbuds (like those used on phones) directly into the jack. If you really want to use those, you would need a TRRS to headphone/mic splitter cable.
----------------------------
Ignore the part below unless you are on the prowl for the Intel spec HD audio jacks. I put this here just for those on google hunts for 3.5mm front panel HD audio jack with isolated switch:
http://www.ab.auone-net.jp/~est/pdf/3.5.pdf (MJ-3335-5)
http://www.temple-star.com/2.5mm_3.5mm_6.4mm_azalia_hd_audio_SMT_Earphone_Jack.htm (The ones marked "HD")
http://www.cui.com/product/resource/sj-3506-smt.pdf
After digging into the Intel HD audio spec, I found that all the jack switches do is insert a fixed resistance value between the Sense_Send pin and ground. Each jack is assigned 1 of 4 resistance values, but each manufacturer may use these values for different jacks. Here is the basic idea:
So, with this in mind, I came up with an idea to cheat and use TRRS (Tip, Ring, Ring, Sleeve) jacks that are much more common. They are available in threaded panel mount, as well as circuit board mount. The idea is, you figure out what values your mobo uses for pin 6 to ground and pin 10 to ground when no audio cables are plugged in. Unplug the front panel from the mobo, as well as any cables you might have plugged into the rear panel, just to be safe. Then you can measure the resistance with a multimeter to figure out what values to use. They should be one of the 4 values above.
Now you can use a circuit like this:
It should work because regular computer headphones/mics use TRS connectors (just one ring) and when you plug them into a TRRS jack, it will short the first ring to ground along with the sleeve. That puts the resistor into the sense_send circuit and tells the motherboard what jack is now occupied.
There is a bonus too: If you use a 4 conductor TRRS extension cable plugged into this front panel, it won't tell the mobo you have something plugged in until you plug into the far end of the extension cable. This allows you to have a remote headphone jack!
The down side is you can't plug TRRS earbuds (like those used on phones) directly into the jack. If you really want to use those, you would need a TRRS to headphone/mic splitter cable.
----------------------------
Ignore the part below unless you are on the prowl for the Intel spec HD audio jacks. I put this here just for those on google hunts for 3.5mm front panel HD audio jack with isolated switch:
http://www.ab.auone-net.jp/~est/pdf/3.5.pdf (MJ-3335-5)
http://www.temple-star.com/2.5mm_3.5mm_6.4mm_azalia_hd_audio_SMT_Earphone_Jack.htm (The ones marked "HD")
http://www.cui.com/product/resource/sj-3506-smt.pdf