Aac transcoding

Didnt see a audio support so decided this would be the appropriate place.
I have Kodio 17.0 installed on a nvidia shield tv and im using a older harmon kardon avr1700 5.1 receiver….i have tried every way to transcode and use passthrough for my reciever to decode the 2.0 sound to get my rear speakers going, but havnt figured it out just yet…can someone tell me settings i need to set it on or at least tell me if it will work with the reciever i have… Thanks