ADAU1701 2nd order noise
Hello
When I generated 2nd order high pass filter in SigmaStudio , the “Read back function block” showed output signal of RMS very huge. and I used a Audio Analyzer, output noise still very huge around 400~600uV, (normal noise showed around 12~14uV). Seems only 2nd order high pass filter abnormal.
Can you help?
There is my testing results in SigmaStudio:
Bypass mode: Okay.
1st order High pass filter Okay.
2nd order High pass filter : NG, noise value showed 400~600uV.
1st order Low pass filter: Okay.
2nd order Low pass filter: Okay.
Test equipments:
Hardware : EVAL-ADAU1701 Rev.A ( Silicon Rev. ADAU1701 XSTZ#0605E)
Audio analyzer. (enable 20KHz LPF)
Software: SigmaStudio rev.3.1 build 9.
Ray.W
Audio Signal Processors
SigmaDSP Audio Processors
adau1701
Hello Ray,
I'm going to guess that you're using single precision filters to do these tests. At low corner frequencies, the performance of single precision filters will be worse than that of double precision filters. I think that you'll probably see an improvement in the noise performance of your 2nd order high pass filter if you make that block double precision, instead of single precision. In the SigmaStudio library, the double precision filters are just another branch under the Filters section of the library.
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