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Old 13 January 2021, 23:03   #64
buggs
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Join Date: May 2016
Location: Rostock/Germany
Posts: 107
Paula's capabilities wrt. actually achievable bit depth in the 14 Bit mode are in the ballpark of 10-11 bit with ECS Paula, depending on the Amiga model. Two major factors contribute to the observed limitations:
a) DAC output levels are not linear with respect to the intended 8 bit source amplitudes
b) the low volume channel is not synchronized in time and actual frequency to the high volume channel due to Paula's implicit resampling at volumes <64

What I disagree with are the estimated noise figures that started this thread. An SNR of 30dB corresponds an effective resolution of less than 5 bits.

My own measurements return different results, consistent with theoretical expectations and existing publications. My baseline measurement in classic 8 Bit resolution landed at 45.8 dB (theoretical optimum: 49.9 dB, old papers around 42 dB). I observed up to 59.6 dB in calibrated 14 Bit mode (A4000) which amounts to a sad hard number of 10 Bit resolution.

With some leniency towards correlated components of the noise figure (i.e. jitter in the low channel), generous rounding and a comparison of the noise floor with 11 bit ideal quantizers, one might be inclined to call it close to 11 bit.

I've updated my Paula writeup with Details to these measurements. The PDF can be found here

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