The MAX98089 uses the SPKVDD voltage internally to generate reference levels. As a result, most signal path configurations will not work as expected without it, however I2C communication and some analog to analog configurations will work without it. As an example, the following oscilloscope screenshots were captured with a setup that routes the analog inputs via the ADC and loop though the DAC to the headphone outputs. One image shows the EVkit with a SPKVDD = 3.7V and the other one with SPKVDD = 0V. The Images have the input signal (CH2) at the top and the output signal (CH1) at the bottom. SPKVDD = 3.7V SPKVDD = 0V