Initially, noise from the headphone cable needs to be suppressed. The PCB’s GND is first connected to the metal case, and then EMI filters are installed. If radiated noise cannot be suppressed using these methods, additional measures must be taken.

If the problem appears to be noise generated from the CD-ROM drive, the source of the noise must be suppressed. The first potential noise sources are the clock and bus lines. Note that noise generated around the oscillator frequently can also cause problems. When noise generated around the D/A converter causes a problem, the point where the analog and digital GNDs are connected must be carefully considered. In many cases, improving this connection often suppresses the noise.

If noise generated from the PC is causing a problem, EMI filters need to be installed on the cable between the PC and CD-ROM drive. Note that the CD-ROM drive may not operate on some computers if large-capacitance or large-inductance EMI filters are used.