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I have a generic handheld dynamic microphone and I want to connect it to my laptop for voice chatting. Normally it should connect to an mic amp and then goes to soundcard's line-in jack.

But my laptop only have a mic jack. Also I've heard that there is a bias voltage around 5V in the mic jack, and the pin definition may vary for different soundcard. After sometime of research I come up with this convert cable. Will it work? If not, what should I do? Is mic amp a must?

Bence Kaulics
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whc2001
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  • an amp is a must, but a lot of soundcards have it built in. – PlasmaHH Dec 19 '17 at 13:55
  • An exact, one letter accurate type of your laptop would be useful. Without it all answers are guesses or have only general things. –  Dec 19 '17 at 13:55
  • @user287001 For my laptop (Lenovo T430s) it's ALC3202 made by Realtek. – whc2001 Dec 19 '17 at 13:57
  • @PlasmaHH Thanks. But how can I bypass the bias voltage? Since some soundcard have bias voltage on the tip of plug and some on the ring, I want to make it universal. – whc2001 Dec 19 '17 at 14:00
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    @whc2001: You don't seem to have any DC path through your microphone, so I don't see what you want to avoid. – PlasmaHH Dec 19 '17 at 14:28
  • @PlasmaHH The microphone 6.5mm jack which only have T and S will short circuit one of the pin in computer's mic jack to ground and cause problems. Finally I tried to create the circuit I sketched above and it seems like that it works. Anyhow, thanks for replying. – whc2001 Dec 19 '17 at 15:20
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    @whc2001: Since on insert the normal 3.5mm will short circuit stuff usually too I am sure whatever provides the bias voltage will be able to deal with that – PlasmaHH Dec 19 '17 at 15:33
  • I used to connet dynamic mic to PC souncard mic input by shorting both Left and Right pins together. AFAIK power output of mic connector has large resistance, so even connecting it to ground causes no trouble. Capacitors on your circuit - another good solution. Mic input has it's own mic amp. – Eugene K Dec 19 '17 at 15:34
  • @PlasmaHH It depends. For my workstation which also have Realtek soundcard, plugging a TS plug into the TRS mic jack have no problem. However on my laptop the chip strangely don't think I plugged anything. – whc2001 Dec 20 '17 at 16:12
  • @whc2001: plug in detection is independent from short circuit protection. – PlasmaHH Dec 20 '17 at 16:16

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Exact schematics are not generally available. I have instead tested other audio mic inputs. DC for mic exists. It is not disconnectable nor adjustable from the Windows Realtek HD Audio user interface. Probably it's adjustable and disconnectable with some utility software, but I haven't met such thing. The DC +3V was connected via at least 6kOhm resistors to tip and ring (=3 and 4) of the 3,5mm plug. There's no DC between 3 and 4. It's only 4 to 2 and 3 to 2.

This is a low voltage version of phantom mic supplying system. I am sure that max. possible 1 mA DC current through a dynamic mic do not cause harm, if you leave the capacitors out and connect one wire of your mic to tip and ring and the other wire to the ground (2). I have done it without realizing there's DC.

Your connection with capacitors should work. It makes sure that the mic does not get DC magnetization. Have high enough capacitances to avoid losing the bass. Remember the right polarity for electrolytics.

  • Thanks for the information and tip. I firstly used 104(0.1uF) ceramic disks and realized the sound quality is bad. After swapped to 10uF electrolytics it worked like a charm. – whc2001 Dec 20 '17 at 16:07