What is the main purpose of having an A-D converter in a sound card?

The main purpose of having an A-D converter in a sound card is to convert analog signals into digital data. Sound is typically captured in an analog form, such as when recording vocal or instrumental sounds through a microphone. The A-D converter processes these analog signals, translating them into a digital format that a computer can understand and manipulate. This conversion is crucial for audio processing, storage, and playback in digital environments.

The other choices reflect functions related to sound management but do not capture the primary function of the A-D converter. Balancing sound levels pertains to mixing and adjusting audio signals rather than conversion. Facilitating sound recording is a broader task that encompasses various processes, but the crucial step of converting the sound from analog to digital is specifically the role of the A-D converter. Switching between different sound outputs involves managing the routing of audio signals rather than conversion, which is a distinct process facilitated by the A-D converter.