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I have a Samsung NOTE 8 (SM-N9500 Android 9).

I have recently tried the Cyrus Soundkey USB DAC/AMP with it and it is excellent for music. However, with phone calls, the Note 8 sends the audio to its built-in speaker/earpiece instead of sending it to the Soundkey. I even tried to force output to USB DAC with 'lesser audioswitch' with no success (see video).

In contrast, the Samsung Note 8 comes with USB-C earphones which can handle both music and calls. I am guessing that these earphones work in 'Audio Accessory Mode' ie. analogue audio straight through USB.

If my assumption is correct :

  1. Why does the Note 8 need to even use analogue output for phone calls when it can output digital audio via USB? Can't the phone call just be routed via a digital path?
  2. Is there a way to disable 'Audio Accessory Mode' and force the Note 8 to use pure digital output for everything including phone calls?
  3. Is there a device that can handle concurrently 'Audio Accessory Mode' and also be a DAC/AMP?

UPDATE #1

I also tried a phone call with the Cyrus Soundkey and a Galaxy A53 (Android 12) phone and it works perfectly! The audio is routed to the DAC and the mic used is the built-in mic inside the phone. So Soundkey is NOT the problem... it must be the android device.

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  • Perhaps its because you are not supposed to record phone calls, which you could do with high fidelity, if it did what you want. Commented Jan 21 at 8:53
  • The Note 8 already has a 3.5mm audio socket, which can be used to record. The 'Audio Accessory Mode' via USB outputs the exact same analogue signal as 3.5mm. If your hypothesis had any truth in it, the phone would also stop me from using my 3.5mm socket.
    – conanDrum
    Commented Jan 21 at 12:12

1 Answer 1

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Devices sold with Google Play Services only need to comply with the version of the Android Compatibility Definition Document (CDD) at the point of initial release rather than any subsequent OS version updates.

So based on GSM Arena's entry on Samsung Note 8 the device was originally sold in 2017 with Android 7.1.1 Nougat. Checking the CDD for Android 7.1 audio output section shows a limited number of requirements.

Now compared with Samsung Galaxy A53 which was released in 2022 with Android 12. Checking the CDD for Android 12 there is a specific section for Digital Audio Ports which may explain the higher compatibility with third party USB digital audio devices.

TLDR: While USB-C audio support started to appear on Android devices before 2017 manufacturers were not obligated until Android 10 CDD, Section 7.8.2.2. Digital Audio Ports regarding compatibility with USB headset interfaces. Sadly older devices probably will not gain compatibility as effort and expense would need to be made by the manufacturer for appropriate audio channel routing.

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  • I read you. However, my main question revolves around comparing and contrasting the behavior of the Note 8 phone calls with a DAC vs USB-C headphones supplied with the Note 8.
    – conanDrum
    Commented Jan 22 at 11:48
  • 'Audio Adapter Accessory Mode' appears in A8 section 7.7.2. USB host mode "STRONGLY RECOMMENDED to NOT support Audio Adapter Accessory Mode as described in the Appendix A of the USB Type-C Cable and Connector Specification Revision 1.2." This suggests that Note 8 does support AAAM. So my questions still stand... 1. Why phone calls use AAAM but music uses DAC, 2. Can we force calls to use DAC, 3. Is there a DAC that handles AAAM?
    – conanDrum
    Commented Jan 22 at 13:37
  • The 1.2 USBC spec mikrocontroller.net/attachment/322860/…, says "Analog audio headsets are supported by multiplexing four analog audio signals onto pins on the USB Type-C™ connector when in the Audio Adapter Accessory Mode.". Further "The analog audio adapter shall identify itself..." and the device's DFP port should detect it. So again, 1. Why phone calls can only use AAAM but music can also use DAC? 2 Can we force calls to use DAC? 3. Is there a DAC that can also handle AAAM?
    – conanDrum
    Commented Jan 22 at 14:05
  • @conanDrum Sadly there have been reports about USB-C headphone incompatibility in the early years,: reddit.com/r/GalaxyNote8/comments/9y5b81/… and in one of the comments a link to a YouTube video describing the issue: youtu.be/Ly-bSBHOSIo with different devices. Presenter did mention the need to enable USB power, I don't know if that is an option or not. Commented Jan 22 at 19:45
  • Thanks for spending the time Morrison. However, please remember that I have an analogue USBC headset that works (music & calls) and a USBC DAC with earphones that also work (but not with calls). Having said that, it looks to be the case that only the manufacturer knows how they executed their implementation. What I would really like to know is why calls do not go to the DAC? Is it because the DAC does not provide a mic? Is it because the phone call encoding is not compatible? what is it? That's what I wanna know. :)
    – conanDrum
    Commented Jan 23 at 0:04

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