I have a full blown Android 13 car head unit - EX-ALS215 (Snapdragon 662). Audio is output from a 3.5mm jack socket on the unit's harness (audio-out socket). I have then connected a Cyrus Soundkey DAC/AMP to one of the USB sockets of the head unit. All audio is now output via the DAC except phone calls and the audio from the AV-IN. (AV-IN is part of the unit's harness and is where I plug my TV tuner as input [Video/L/R]) So, voice calls and AV-IN persist in coming out of the 'audio-out' socket on the harness.

Why is this happening and how can all audio be routed to USB?

Clue#1: I have tested the Cyrus Soundkey with a Samsung Galaxy A53 and when making a phone call the audio from the call was correctly routed to the earphones plugged into the DAC. The microphone used during the call was the one built into the A53. I am at a loss as to what is happening.

UPDATE#1 (01 Feb 2024): I used adb to investigate why this is happening. Can you see anything obvious in the text files? or Would you like me to try something else?


  1. I am no expert, but is dumpsys audio showing the "Cyrus Soundkey" (usb_headset(4000000)) being the default for voice calls? post.com/forums/attachment.php?attachmentid=3377686&d=1706801391

  2. dumpsys media_session: shows the com.wits.ksw.bt application (the KSW BT dialer) making a voice call? Does this mean that kswBt tries to output to the Soundkey and it fails, defaulting back to the builtin speakerphone (as seen in practice)? UPDATE: This entry does NOT represent a phone call. Instead it represents BT audio played on my phone via this BT app which is also responsible for voice calls. Indeed BT audio from my phone played using this app, does go through the USB DAC.


  1. Is it possible that the Soundkey is being rejected due to an audio incompatibility with the telephony audio (24bit vs 16bit or something)?
  2. Someone suggested that A FiiO Q3 DAC would work with voice calls because it supports USB Audio Class 1.0. Others have said that a FiiO K3 DAC which also supports USB Audio Class 1.0 exhibited the same problem with voice calls. (FYI. The former has a unit from same manufacturer as mine, bought 2 years ago and upgraded to A13 & current firmware. The latter was from same manufacturer in 2020 A10.)

LINKS TO FILES: dumpsys audio, media.audio_policy, dumpsys media_session, media.audio_flinger.

  • Be aware that 'Android car head unit' can mean slightly different things, see androidpolice.com/… for an explanation of differences. Commented Jan 25 at 3:20
  • Please clarify. The statements are contradictory about phone calls and audio In. Please explain what a head unit is. Commented Jan 25 at 10:59
  • I have added a link and some more details in my question above. If you need more info, tell me. I have hardware screenshots etc. Anything you want tell me.
    – conanDrum
    Commented Jan 25 at 11:50

1 Answer 1


It looks like after more than a week and 77 views and a bounty of 50, there has been no response.

Today I received the FiiO Q3 which someone claimed would work with voice calls because it supports USB Audio Class 1.0 {16bit} (press 'Gain' button while connecting it to USB). I tried it both in default mode {32bit} and UAC1.0 mode {16bit} and nothing changed. ie. Whatever the behavior of the Cyrus Soundkey was, the Q3 replicated it exactly. No magical improvement in the audio routing.

The voice calls were still routed to the harness, instead of to the DAC. Same thing with DTV audio - still routed to the harness, instead of to the DAC.

My conclusion is that the com.wits.ksw.bt application (the KSW BT dialer) and the DTV application are both hardcoded to specifically use the internal speaker output disregarding any other output. I suppose that person that claimed that the FiiO Q3 was able to overcome this problem was either totally mistaken or his android HU was substantially different (e.g. mine is CCC while his is CCI).

Further detailed info can be found in this thread between these 2 posts: https://f30.bimmerpost.com/forums/showthread.php?p=30805968 https://f30.bimmerpost.com/forums/showthread.php?p=30891352

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