Archive for March 24th, 2016
Bose QC20 Noise-cancelling Headphone Signals
Posted by Ed in Electronics Workbench on 2016-03-24
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
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:
- Volume + = 220 Ω
- Answer/End = 56 Ω
- Volume – = 520 Ω
Now, if only I had a device that would do something with those signals …
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