AD1940,ADAU1446 - Output noise
Sirs
Testing the AD1940 and ADAU1446 Evaluations Boards, with a simple circuit (in directly to out), just using one channel (mono), I put a 1Khz sinus at input, and check the output test pin (with no loads). Let's see the signal. I've noted a noise over output signal at 45 Khz (AD1940) and 22 Khz (ADAU1446). Both running at 48 Khz (sampling rate). So I need a help if is normal, and how to avoid this.
Regards
Jean Fernandes
ad1940
Audio Signal Processors
adau1446
SigmaDSP Audio Processors
Hi Jean,
This is due to the digital interpolation filter in the DAC. It is part of a tradeoff between die area, power, group delay, and performance. Note that this is well above the audio frequency range and it is about -75 dB relative to the operating level of the system; therefore, it is inaudible. If you want to remove this component, then use a steeper analog filter after the DAC output.
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Thank you,
EZ Admin
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