Abstract: In a phase synchronizing loop apparatus for digital audio signals, a clock operation is controlled in accordance with a plurality of audio data formats, allowing a data transmission clock to be generated using a phase synchronizing loop. The apparatus includes an edge detector for detecting an edge of applied data, a clock generator for retaining the signal from the edge detector for a predetermined period of time to generate a clock signal, first and second phase synchronizing loops for detecting a phase difference between the clock signal and the oscillation output of a voltage controlled oscillator, a controller for generating a control signal in accordance with the audio data formats, and a display for discriminating a synchronization state and displaying an indication thereof.