Assuming you want to play the Audya using the SD7's speakers ....

Connect Left Main output of Audya to Guitar in (Mic2) in on SD7. On SD7, go to Mic2/Guit IN (press and hold for 2 seconds) and make sure input is set to GUITAR and NOT mic. Turn up gain about 70%. Turn up Audya volume to max 50%!!!

Now play your Audya, and it will be heard through the internal speakers of the SD7 and any amplification connected to the SD7. That should do it.

Thanks,