Mic & Headset Splitter for Smartphones and Tablets

Hi everyone,

since I released the new spectrum/waterfall features, I’ve been asked how to get audio in the android device.

Most of the devices have a mic embedded in the earphones jack. Not all but many.

Personally I have a Nexus 7 2013 that has and a Motorola Moto G that (unfortunately) doesn’t.

When you have a device like the Nexus 7 2013, the solution is very simple and cheap.

Here’s a schematic I’ve found showing the pinout (it is the same for iPhones and iPads).



You can find various commercial solution costing around $4-$6 like this one:


Or build a cable yourself:


Before that, please check:

  • your device had an audio in “hidden” in the earphones jack
  • the pinout of your audio jack as in some devices the pinout can be different

If your device DOESN’T have a mic port embedded in the earphones jack, there another solution: using an external USB Sound card.

If you are already using the microUSB port to connect the device to the KX3 via OTG-USB Serial cables, you need a small USB hub so that you can attach more USB tools to your device.

Again, I personally use an Axus Xonar U3 USB sound card that is a very good one with very low noise and perfect for radio uses. Not a cheap solution but not expensive if compared to other quality USB sound card with the same features.

If you’re going to use the an external USB sound card make sure that it supports 48 Khz – 16 bit sampling rate as that is the settings I’m using for the actual versions of the KX3 Companion. In the future I’ll add options to change them manually if you need.

If you have more solutions let me know 😉

Enjoy the spectrum/waterfall with touch QSY!

72/73, Andrea IU4APC


10 thoughts on “Mic & Headset Splitter for Smartphones and Tablets

  1. Pingback: KX3 Companion | Future Development

  2. Did this work with your nexus 7? I have a nexus 7 and the same sonar USB card. I can only get apps specifically written to use USB audio to use the device. I cannot get apps to use the xonar by default.

    • You can’t use the Xonar USB card with it now.
      But you can use the “splitter” cable with the Nexus 7 2013 so that you have both audio in and out.
      73 Andrea IU4APC

  3. Thanks. From playing with devices this morning and lots of trial and error, I realize Android support is spotty! On my MotoX, the Xonar output works, but not the input with most stock apps.

    Unfortunately I own a 2012 Nexus 7, which has no audio input. I think I’ll have to buy another one on eBay …

    On a related note, since upgrading to Lollipop a lot of my apps were slow and sometimes not responsive, including KX3 Companion. It would often lock up after 5-15 minutes after the Lollipop upgrade. Other apps using devices sometimes did this too.

    I downgraded my Nexus to an older more minimal setup (CM 10.2, Android 4.3) and your app works great. Lollipop made my Nexus barely usable …

    • Nexus 7 2012 doesn’t have the audio in in the earphones port I know (I know both the 2013 and 2012 version).
      I still have to work on the USB audio in support. There are not many info our there but I’do in the future. Can’t tell you when 🙂

  4. Unfortunately I own a 2012 Nexus which has a microphone but no audio input on the audio jack. Why they did this, I do not know! I may just buy another on eBay …

  5. Andrea, thank you for the great app KX3 Companion. I have a question. I am building a cable that would connect KX3’s audio output to the audio input of Nexus 7 2013. On the picture of your radio setup (https://kx3companion.files.wordpress.com/2014/03/banner-large.jpg) there are two audio cables connecting from KX3’s I/Q and MIC to the Y-split cable connecting to the 4-pin plug on the tablet.

    Question 1: Why do you need to connect to the MIC input of the KX3 radio?

    Question 2: Did you connect one of the quadrature I/Q outputs of KX3 to the microphone input of the tablet? Nexus 7 2013 has a mono microphone. Is connecting just one of the quadrature signal pair enough for proper operation of the waterfall display? You mentioned somewhere on this website that I/Q output should be used for wider spectrum settings of waterfall display.

    Also, just a small comment, I noticed that you put an RF choke on the serial cable at KX3’s ACC1 input – this is a good idea as the USB/Serial adapter generates RFI on multiple amateur bands.

    Thank you for your support,

    Leo, KZ8E

    • Ciao Leo,
      here are my answers:

      1) Because I also use other apps to send signals like my WSPR Beacon app 😉

      2) For now we have to go with mono. But with Android 5 we are supposed to be able to use external USB audio cards. But I haven’t tested them extensively so to integrate the support of the full I/Q in the app yet.

      About the RF Choke (with ferrite) you’re right. It helps “cleaning” things a little 😉

      72/73 Andrea IU4APC

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s