Bose QC20 Noise-cancelling Headphone Signals

Bose QuietComfort QC20 Noise Canceling headphones (they’re actually earbuds) come in Apple and Android versions that (probably) differ only in the connector pinout. Given that the connector has four conductors, I was surprised to find only half a dozen different possibilities, with only two for purely audio connectors.

These QC20 earbuds came in the Android flavor, also known as the CTIA/AHJ “standard”:

Bose QC20 Earphones

Bose QC20 Earphones

The 3.5 mm plug connections:

  • Tip = left audio
  • Ring 1 = right audio
  • Ring 2 = ground
  • Sleeve = microphone and button signals

The blue Mode button on the side of the splitter box switches the noise cancelling between “some” and “silent”. The latter works surprisingly well; it can knock our vacuum cleaner down to a bearable level.

The three black buttons place resistive loads on the otherwise open-circuit microphone connection:

  1. Volume + = 220 Ω
  2. Answer/End = 56 Ω
  3. Volume – = 520 Ω

Now, if only I had a device that would do something with those signals …

  1. #1 by Mike on 2016-03-24 - 14:34

    If you wanted to send them my way I’d be happy to use those buds on my phone….

    But actually I can see using one of the A-to-D inputs on a Raspberry Pi Zero ($5)
    in voltage-divider mode to determine which button was being pressed and take
    appropriate action.

    • #2 by Ed on 2016-03-24 - 15:59

      Hah! Not a chance!

      I’m considering a GNU Radio project for audio-frequency signal processing to boost my deflicted hearing, as opposed to dropping $5k on a pair of un-tinkerable ear beetles. I’m the type of guy who wouldn’t mind deploying a microphone array to hear with adaptive beam-forming…

      Mary says they remove surrounding bass and midrange to leave annoyingly audible treble. That’s not a problem for me.

      • #3 by eriklscott on 2016-03-24 - 17:30

        Adam Savage talks about his hearing aids, and they have an electronic beam former mode: . You may not need an actual microphone array.

        • #4 by Ed on 2016-03-24 - 20:21

          His rant toward the end is exactly my starting point …

          • #5 by david on 2016-03-25 - 10:33

            The irony of there being no transcript of that episodes is just about killing me. Sigh.

            • #6 by Ed on 2016-03-25 - 13:09

              Given all the gesturing and expostulating, there may be no words for that discussion: hand it to Google’s voice-to-text project and watch what emerges…

            • #7 by eriklscott on 2016-03-25 - 18:17

              At least it’s closed captioned (close captioned? usage?). Turn on captioning in YouTube (click the “gear” icon, hit the settings). I can’t remember if was one of the editors or one of the readers, but it went up a few days later. Not that I completely trust my memory, but it really seems like this one was done by hand and by ear. And as mentioned below, these podcasts benefit from being seen and not just heard.