Expander on FDSP of 1787, SigmaStudio
Thread Summary
The user inquired about the operation of the expander with external detect for the ADAU1787 FDSP, noting a lack of documentation. The support engineer provided the limiter documentation, suggesting the expander functions similarly but applies gain changes below the threshold. The accompanying answer noted that the expander behaves more like a hysteresis gain and requested additional documentation on the SigmaStudio wiki page.AI Generated Content
SigmaStudio lists an expander for the 1787 FDSP, but I cannot find any documentation on how it operates. I am specifically interested in the expander with external detect. I have played with various inputs and parameter settings but in the end the block was not operating as expected. It would be very helpful to have some clear definition of the pin and parameter functions. Anyone at ADI can help with that?
Cheers.
software
ADAU1787
adau1772
1787
Integrated/Special Purpose A/D Converters
4.5
Audio CODECs
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Hello User2,
Thanks for pointing out the missing documentation. Back in 2020 we documented the limiter for the ADAU1787 and a few years before that I had documented the limiter for the ADAU1772. The expander is new with the ADAU1787. I will attach the document about how the limiter works. These basically are comparators to compare levels then apply a gain correction. I would expect the expander to be almost the same except the gain change would happen below the threshold instead of above.
Dave T
Here is the limiter documentation.
Could some documentation be added about the expander on the SigmaStudio wiki page/ documentation. We struggled for quite some time until we realized the expander functionned closer to some sort of hysteresis gain instead of an expander.
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