The CTRL pin is typically connected to the Bluetooth MUTE pin to enable mute control from the host or Bluetooth module. This arrangement simplifies mute management in Bluetooth audio applications and helps ensure quiet operation when needed. The power amplifier board ships in ACF1 mode by default, providing standard operation out of the box. If you plan to use the CTRL mode setting, remove (desolder) resistor R5 to switch from the default ACF1 configuration to CTRL mode. Key attributes Function: CTRL to MUTE connection enables mute control for Bluetooth audio. Compatibility: Designed to work with Bluetooth mute signaling through the CTRL/MUTE interface. Configuration: Default is ACF1 mode; CTRL mode requires removing R5. Setup: Straightforward change to enable CTRL mode with a simple resistor removal. Use scenarios Home audio systems: Integrate with a Bluetooth receiver or speaker to mute the amplifier when needed, such as during Bluetooth pairing or when playback starts and stops. Soundbars and portable speakers: Enable external mute control from a TV or control unit by configuring CTRL mode. AV installations and displays: Use CTRL to mute the amplifier during system announcements or source changes, ensuring clear audio transitions.