Before ditching an audio effects unit Boss DD6 ( main 100 pin BOSS chip failed) I wanted to see if the DAC was still working . I cut data-in line, pin 4 of DAC AK4352VT from the main Boss chip and connected , via 1K, to pin 9 , data out of the ADC AK5353VT.
Feeding sine in the datastream varies on frequency. No data into the DAC then nothing out. Connect datastream and there is 2V peak limited white noise on the analogue outputs, left and right channels. Varying sine input or even disconnecting makes no observable difference to the noise output. Scope shows no obvious periodicity 100Hz to 100KHz, and sounds like white noise. Other select lines are still connected but what , in principle, is occuring ?