Simple Audio Player_Using only DAC0 or DAC1

Hello Everyone,

I am using Simple Audio player for Arduino Due with LM4875 amplifier, I want to use DAC0 as a Audio channel and DAC1 to control gain of the amplifier. During playing with 44100 Sample rate MONO, I checked both channels by oscilloscope and I can see the sound in both channels.

Could you please help me, how to use DAC1 to control the gain of the amplifier.

Thank You,