No. The Blustream ADC11AU does not have a volume control, and varying the level of the analogue signal going into it does not provide a volume-control function on the Toslink output in the way a volume-controlled DAC or digital processor would. If a variable analogue input signal goes into it, the output is the same. You should be mindful of exceeding the ADC's maximum input level to avoid clipping and adjust the variable level accordingly. Normal line-level signals should be fine.