The SPD-SX PRO features a function (called "Rec Auto Trigger") that automatically starts sampling when an input signal is detected. When recording a sample using the Rec Auto Trigger function, the sample's sound may not start exactly as intended.
If the sample doesn't start playing when it should, adjust the waveform start point on the WAVE EDIT screen and then save the sample. For details on how to use this function, refer to “Editing and Saving a Sampled Waveform (WAVE EDIT)”.