PC audio cabling: In a classic desktop PC, the analog CD-ROM audio cable should be connected to which internal component to route CD audio to speakers?

Introduction / Context:
Older PCs used an internal analog audio cable from the optical drive to the system’s audio subsystem for CD playback. Although modern systems stream audio digitally over SATA or the data bus, understanding legacy connections remains important for maintaining and restoring older machines.

Given Data / Assumptions:

• Scenario involves a system with an optical drive and discrete or integrated audio.
• We refer to the small 3- or 4-pin internal analog cable historically used for CD audio.
• Goal: identify the correct termination point inside the PC.

Concept / Approach:

The analog audio output of the CD-ROM connects to the audio input header on the sound card or, for motherboards with integrated audio, to the board’s CD-IN header. This routes analog audio to the DAC/output stage feeding speakers or line out.

Step-by-Step Solution:

Verification / Alternative check:

Playing an audio CD should produce sound through the PC’s speakers when the mixer input is enabled. If using digital extraction in modern OSs, the analog cable may be unnecessary, but historically this connection was required.

Why Other Options Are Wrong:

• Power supply: provides power, not audio signal routing.
• Speaker directly: internal speaker headers are not designed for CD audio input.
• Hard drive: unrelated to audio signal paths.
• BIOS: firmware configuration area; no physical audio input.

Common Pitfalls:

Connecting to the wrong motherboard header (e.g., front-panel audio vs. CD-IN) or forgetting to unmute the CD audio channel in software.

Final Answer:

Sound card (or the motherboard’s audio header if integrated)