fantastic dac and fantastic review. I love that test with sin wave at noise floor for 16bit. Why though 997hz?
Got my answer from GPT.
Choosing 997 Hz instead of a round 1,000 Hz for test signals is a practice that stems from the early days of audio engineering. This specific frequency can help avoid synchronization issues with test equipment that might be operating on cycles synchronized to a 1 kHz tone, which is a multiple of power line frequencies in many countries (like 50 Hz or 60 Hz). By using a frequency like 997 Hz, which is prime and not harmonically related to power line frequencies, it reduces the chance of interference in the measurements from external sources.
The specific level of -90.31 dBFS instead of a round -90 dBFS might be used for several reasons:
1. **Precision**: -90.31 dB could be the result of a specific test setup where the output level happens to be -90.31 dB, and the testers are reporting the exact figure for accuracy.
2. **Standardized Test Levels**: It could also be a standardized level from a specific testing methodology or protocol that aims to challenge the DAC with a very precise and potentially non-standard level to check its performance under more unique conditions.
3. **Reference Recordings**: Some test tones or reference recordings come at preset levels, and the tester might have used one such tone that is calibrated at -90.31 dBFS.
The reason for such precision is to ensure consistency and repeatability in testing. When comparing multiple devices or conducting multiple tests over time, having exact figures allows testers to notice the smallest differences or changes in performance.
