Four-Conductor, Headphone + Mic Jacks
-
- KVRAF
- 2285 posts since 20 Dec, 2002 from The Benighted States of Trumpistan
Tech question here. My laptop and iPad have those shitty headphone/mic combo jacks, and I'd like to screw around playing guitar whilst watching videos. (Call it modern ADHD.) I have a decent audio interface, but I don't feel like lugging it around everywhere I go. So, how do you get them to actually work? I got myself a cable that joins an 1/8" stereo and 1/8" mono jacks into a single four-conductor plug, but it works on neither my iPad nor laptop (IIRC there are competing standards for the third and fourth conductor). I can't get either device to even recognize there's more than headphones present. What am I missing?
Wait... loot _then_ burn? D'oh!
-
- KVRAF
- 16826 posts since 8 Mar, 2005 from Utrecht, Holland
We call these connectors TRRS - Tip-Ring-Ring-Sleeve.
Just got out my multimeter to figure out the pinout. Using a Samsung set of earbuds with mic, and they work OK on my MacBookPro and obviously Samsung phones. Never tried them on an iPhone or iPad or other laptop than MBP.
The ring closest to sleeve seems to be the common ground, I measure 60 Ω between that ring and the tip or first ring. So these are the left & right signals for the headphones. That leaves sleeve with second ring being the mike, I measured 1.6 kΩ which is normal for a dynamic mic. So it seems these buds are of the CTIA standard pinout, quick google indicates that's also the iPad pinout.
What I think is happening, is that your guitar has not the right impedance for your device to sense a mike is present. Usually electric guitars (passive pickups, no active battery-driven electronics) have a high impedance of around 1 MΩ.
The device should be backwards compatible with standard TRS headphones. One way to sense that is to measure resistance over the sleeve and last ring. When that is zero, then there is no mike. Perhaps you have a fault in the soldering and made short-circuit between sleeve and the last ring. Easy to check if you have a multimeter.
Another theory is that the impedance is too high. The mic-sensing circuit may measure a too low voltage and concludes the cable to the mic is broken. You can test this theory by mounting a 1.6 kΩ resistor on the mic connections.
Did you buy them or made it yourself?Jafo wrote: Fri Jun 04, 2021 1:19 am I got myself a cable that joins an 1/8" stereo and 1/8" mono jacks into a single four-conductor plug
Just got out my multimeter to figure out the pinout. Using a Samsung set of earbuds with mic, and they work OK on my MacBookPro and obviously Samsung phones. Never tried them on an iPhone or iPad or other laptop than MBP.
The ring closest to sleeve seems to be the common ground, I measure 60 Ω between that ring and the tip or first ring. So these are the left & right signals for the headphones. That leaves sleeve with second ring being the mike, I measured 1.6 kΩ which is normal for a dynamic mic. So it seems these buds are of the CTIA standard pinout, quick google indicates that's also the iPad pinout.
What I think is happening, is that your guitar has not the right impedance for your device to sense a mike is present. Usually electric guitars (passive pickups, no active battery-driven electronics) have a high impedance of around 1 MΩ.
The device should be backwards compatible with standard TRS headphones. One way to sense that is to measure resistance over the sleeve and last ring. When that is zero, then there is no mike. Perhaps you have a fault in the soldering and made short-circuit between sleeve and the last ring. Easy to check if you have a multimeter.
Another theory is that the impedance is too high. The mic-sensing circuit may measure a too low voltage and concludes the cable to the mic is broken. You can test this theory by mounting a 1.6 kΩ resistor on the mic connections.
We are the KVR collective. Resistance is futile. You will be assimilated. 
My MusicCalc is served over https!!
My MusicCalc is served over https!!
-
- KVRAF
- Topic Starter
- 2285 posts since 20 Dec, 2002 from The Benighted States of Trumpistan
Hello. Wasted money on a Dukabel premade; it has two jacks, one marked for headphones and the other for a mic. Impedance seemed promising, but I get the same (lack of) result even with a direct box or a preamp, so drat. Followed your example more closely, and found that they switched conductors on the mic input. Unfortunate, but that's why soldering irons exist. Should be workable. Thanks for the advice!
Wait... loot _then_ burn? D'oh!