If you ever experience warbles and/or pops when CD Scratch is playing you may need to calibrate your soundcard.
Note: The audio output device calibration settings only apply to true WDM drivers.
Click the button in the CD Scratch window. This will open the Output Configuration dialog box.
Click the Cal button for the "ON AIR" output device.
In the Optimize Buffering section you will need to adjust the Optimize buffering slider to suit your system.
The idea is to lower latency, but without getting any cracks and pops. Position the slider after (to the right of) the region that causes the cracks and pops. Since this function is circular in how it works internally, the optimum position may actually be near the left of the slider (if the region of cracks and pops is to the far right).
Be sure to test your chosen setting under heavy system load, as some positions may seem fine until your system is loaded. Leaving a space of about 20 percentage points between the end of the region of cracks and pops and the position of the slider is usually optimum.
If your soundcard appears in the Output device list as a Legacy type, then you will normally be better off using it via the Legacy means, rather than the WDM.
How to set up your soundcard (main channel)
Output Configuration dialog box
Audio output FAQ