It is a fancy word for volume control. 
Volume control is tyically done in the amplifier and not in the player. This yamaha supports volume control also using a remote and through app. You can just connect power speakers and control volume from yamaha rather than running to the speakers every time.

Volume control is tyically done in the amplifier and not in the player. This yamaha supports volume control also using a remote and through app. You can just connect power speakers and control volume from yamaha rather than running to the speakers every time.
Hi blasto , I dont know what is preamp and how is it used , will be glad if can do or post a link to the guide on how to use it.