PCM1808 ADC frequency response not flat

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elskardio

Well-known member
Joined
Sep 29, 2010
Messages
562
Location
Montreal - Canada
Hi Guys,

I'm presently experimenting with the PCM1808 ADC. The schematic is identical to the Datasheet.

The frequency response is far from flat in the top end. (please see the attached image, captured at 48KHz)

Looking at the curve, it's almost like there's a LPF with a -3dB point at 44Khz.

Should i be able to get a flat response from this ADC or it has limitations?

Thanks for your input

PCM1808-freq.jpg
 
Id been meaning to buy in a couple of those boards for testing myself . Theres also a PCM1802 board for a few euros on ebay which I think has slightly better noise/thd specs than the 1808.
So thats interesting you have level frequency response to around 22khz @48khz FS.
Could you repeat your tests at 96khz ?
PCM1802 quotes SNR as 105db , parraleling the inputs might get you 3db better and perhaps a balanced input using both channels push/pull might improve performance by another small but usefull margin.
Keep up the good work . 



 

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