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ADC filter response at 16000

The ADC filter response is important when acquiring sample data from an audio device.  It determines the flatness of the frequency pass-band and the amount of aliasing distortion.  The quality of a device's LPF and sample rate converter can be summarized in a single spectrum image.

The methods used to create the spectral plots below are described in the Swept Sine vs. WGN application note.  The orange curve represents the pass-band frequency response which from 0 Hz (DC) to the Nyquist frequency.  The cyan curve is folded frequency which represent alias rejection past the Nyquist point.  The purple curve is the noise floor.  The occasional green curve is a pure sine wave that is used for distortion measurements.

This gallery is part of the Full Duplex DAQ comparison survey. 

Cirrus Logic CS4236B Sound Blaster Vibra16X

Sound Blaster 16 PCI Sound Blaster 128 Sound Blaster Live!

VIA 8235 SiS 7012 ESS Maestro 2E

Griffin iMic v0.06 Griffin iMic v3.00

Some devices such as the VIA 8235, SiS 7012, and the ESS Maestro 2E have nonexistent anti-alias filters (flat folded cyan curves).  Both the VIA and the SiS products use a Realtek codec but it is not sure that the decimation stage is being processed there..

The Sound Blaster 16 PCI and 128 which are both based on Creative's ES1371 chipset have identical looking spectral plots.  The folded cyan curves show fairly shallow anti-alias roll off.

The Sound Blaster Live! and both revisions of the Griffin iMic have very sharp anti-alias roll offs.  The two iMics have the most attenuation (-80 dB with v0.06) and the sharpest roll off (v3.00).

Out of the above bunch of cards, the only ones recommended to record at the 16000 sample rate are the CS4236B, SB Vibra16X, SB Live!, and both iMics.

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