The preamp is in the cabinet under the main TV in the living room.
Using the knob, you can switch between the following audio inputs:
Sat - use this input for watching the TV
BD - use this input for connecting a source via Bluetooth
Aux2 - use this source to ask Alexa to play music. There are high quality B&W speakers in most of the rooms in the upstairs portion of the house and a manual volume control knob on the wall. Alexa is connected to a subscription of Napster.