ADAU1761 output noise
Thread Summary
The user measures a 97 dB(A) dynamic range with a digital sine wave generator (0 dBFS peak) and MX5G3 and LOUTVOL at 0 dB, but the datasheet specifies 101 dB(A). Increasing MX5G3 to +6 dB and LOUTVOL to +2 dB achieves the 101 dB(A) dynamic range. The support engineer suggests that the initial measurement may be limited by the sine wave generator's interpolation noise, and recommends bypassing the DSP for accurate analog noise measurement.AI Generated Content
If I create a digital sine wave generator in the DSP (0 dBFS peak), and measure at the output with MX5G3 at 0 dB and LOUTVOL at 0 dB, I get 97 dB(A) dynamic range turning the generator on and off, while the datasheet says 101 dB(A). If I raise MX5G3 to +6 dB, and LOUTVOL to +2 dB (right before clipping), I get 101 dB(A) dynamic range. Are these the conditions you measured at? Should I leave it at these gains for production to get the best noise floor, or will it vary significantly from unit to unit?
When the button says "Line Out", does that mean "currently in Line Out mode" or does it mean "press to switch to Line Out mode"?
Audio Signal Processors
noise_floor
noise
SigmaDSP Audio Processors
adau1761
dac
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Hi J3627
Please be aware that you might be getting into the limitations for the digital sine wave generator and not the DAC. It's implementation (for instruction minimization purposes) was done using interpolation of a sine tone built on ROM and therefore the noise that you might be measuring may be caused by this interpolation. To measure Analog Noise, it is better to bypass the DSP.
Regards
Miguel
Well I'm measuring the noise with the sine wave generator turned off, so hopefully it's just generating zeros at that point. (For the record, the THD+N of the sine wave at full scale was -82.8 dB = 0.007%, with the "G3" algorithm.)
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EZ Admin
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