Questions: Analog-to-Digital Conversion in Audio

Question 1

What is the purpose of the anti-aliasing filter in an ADC?

• A. To boost the signal before sampling
• B. To remove frequencies above the Nyquist limit before the signal is sampled
• C. To add harmonic warmth to the digital signal
• D. To convert the sample rate to a standard value

Answer: (B)

Without anti-aliasing filtering, frequencies above Nyquist would fold back into the audible range as aliasing artifacts. The low-pass filter prevents this before sampling occurs.

Question 2

True or false: Jitter in the sample clock primarily affects low-frequency content.

• T. True
• F. False

Answer: False

Jitter causes timing errors in the sampling process, which manifest as sidebands around high-frequency tones. High frequencies are most sensitive because small timing errors represent a larger phase error at higher frequencies.

Question 3

What does dynamic range mean in the context of an audio converter, and how does bit depth affect it?

Model answer: Dynamic range is the ratio between the loudest undistorted signal and the noise floor, measured in dB. Each bit of depth adds approximately 6 dB of dynamic range — so 24-bit achieves about 144 dB versus 96 dB for 16-bit.

Greater dynamic range means the converter can handle both very quiet and very loud signals within a single recording, which is critical for sources with wide dynamic variation like acoustic instruments.

Question 4

A studio records at 24-bit/96 kHz using multiple converters. What synchronization measure prevents audible timing artifacts?

• A. Using identical cable lengths on all inputs
• B. Recording each converter in a separate session
• C. Slaving all converters to a single master word clock
• D. Enabling oversampling in the DAW

Answer: (C)

Multiple converters running on independent internal clocks drift relative to each other, causing inter-channel jitter and timing offsets. A master word clock synchronizes all converters to a common timing source.