With the latest firmware update for Spark 2, you can now adjust the line-out behavior directly in the Spark app! Follow these steps:
1. Update the Spark app to the latest version
2. Connect your Spark 2 to the Spark app.
3. Go to the Menu tab and tap on the product card.
4. Turn off the "Line Out Mute Behavior".
*On is muted, off is unmuted.