Quote:
Originally Posted by DuraMorte
Try your old 8kHz test at 40Hz, and see what happens. But don't just look at the frequency graph; also check the waveforms.
A 40Hz sine wave gained up to -.1dBFS at the input could saturate the input and cause sagging, flatlined garbage... and the clip LED will never light up.
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Here is the 40Hz recorded at -0.2dBFS (as close as I could get without occasional clipping):
Here is the 40Hz recorded at -18 (peaks, so maybe -21 RMS):
...looks like the -18 signal resulted in a distortion spike at roughly 520Hz and just a bit more noise in the high frequencies. The distortion spike is in line with what Jim Williams said about most converters having less THD at hotter levels (see post #41).
The waveforms look identical (this is a representative slice):