PCM5121: Biquad high frequency EQ point issue

Anderson Cheng

Part Number: PCM5121

Hi Expert,

when I use the PCM5121 GDE GUI to configure the Biquad, I found strange issue when I add high frequency EQ point.

1. EQ setting 1000Hz,10dB,Q=2, I can get the expected Graph as below.

2. when change the EQ frequency to 10Khz or even higher , the full band gain is dropped, this is not expected. and customer's test data is matching the PPS Graph showed result. but why?

Please help me to fix this or explain the reason.

thanks.

Anderson

over 2 years ago

0 Arthur Brown over 2 years ago

TI__Mastermind 19585 points

Hi Anderson,

I found this E2E thread which is discussing a similar issue. https://e2e.ti.com/support/audio-group/audio/f/audio-forum/968024/tlv320aic3206-overflow-in-biquads-in-tlv320aic3206

can you share the filter coefficients for both of the filters you have shown here? I think that the filter design tool is normalizing the coefficients such that no coef' exceeds 1, (or 0x7fffff)

You should be able to achieve 0dB in the flat region by adjusting the scale factor in the right column.

From the thread I linked it you should set the scale factor as 1/.6489 = 1.5410

Regards,

Arthur

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PCM5121: Biquad high frequency EQ point issue