Add this 'AIM Option 4 - AI16' to your Symphony chassis to get 16 Analog IN + 16 Optical OUT (16 channels of Analog INPUT and up to 16 channels of Digital OUTPUT simultaneously). The I/O Modules are the sound and soul of Symphony I/O, and represent 25 years of Apogee R&D and design excellence. These powerful Modules deliver Apogee's core competency, superior sounding digital audio recording. With 5 available I/O Modules, you can choose from standard configurations or customize the following: channel count, analog to digital input, digital to analog output, mic preamps and digital I/O. You compose your Symphony I/O.