Hi @SLO hombre,
Welcome to the Sonos community and thanks for letting us know about your concern. Let me share some information to help you out.
The Sonos Port has a built-in DAC, which you can connect to your existing setup for playback. You can adjust the settings in the Sonos app or on your Yamaha RX-A740 home theatre receiver. In the Sonos app, you can adjust the bass, treble, balance, and loudness and change the way you control the volume of your Port using the Line-Out Level settings on one of the options.
- Fixed - Set Port’s line-out level to Fixed if you want to control the volume exclusively from your amplifier or receiver. You won’t be able to use the Sonos app to adjust the volume or equalization settings.
- Variable - When Port’s line-out level is set to Variable, you can use the Sonos app to adjust the volume.
- Pass-Through - When Port’s line-out level is set to Pass-Through, Port stays at a fixed volume and sends volume commands to amplifiers that support pass-through. You can control volume using the Sonos app, a universal remote, or your voice if you have a voice assistant enabled.
You can try to set the Line-Out setting as Fixed to control the volume on your Yamaha RX-A740 and change the sound settings if you can get Dolby Pro. We can also wait for suggestions and feedback from our Sonos community members, they might have inputs about this.
If you need help with any other information, please be sure to let us know.