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Old 14 January 2021, 00:48   #66
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Join Date: May 2016
Location: Rostock/Germany
Posts: 107
Originally Posted by chb View Post
I do not think that pre-emphasis would have any effect on a 441 Hz signal, as it is well below the LPF frequency. But his improved calibration may.

True, any frequency well below the 3dB cutoff is unimpeded.

The pre-emphasis has to compensate for 15 dB attenuation around 18 kHz (A500/2000/4000), 12 dB for A3000 and 4 dB for A1200. The latter is hardly of consequence, ofc. But this process involves a trade-off between the dynamic range of the output signal and filter headroom. A near flat frequency response out of an Amiga is nice but won't help wrt. SNR. That's why I left it out of my experiments.

Concerning the calibration update: I don't expect a large impact on measurements with sine tones at 0 dBFS. I've only noticed (and disliked) the quantization table issue with signals of low amplitudes.
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