Adding TOSLINK / optical input to 1701 project?

I have an older design using an ADAU1701, and we'd like to upgrade it to include consumer-grade TOSLINK (optical input), but I don't want to add too much cost.  From my reading, this gets complicated, because the master clock for the ADAU won't be synchronized with the external source.  So I assume I'll need an ASRC.

I see a few options -

1.  Add a chip to convert S/PDIF to I2S as a slave to the source, then use an ASRC to sync the digital data into the ADAU1701.  This seems quite complicated, but maybe there's a cheap IC somewhere that does all this?

2.  Convert the S/PDIF into analog, which is mux'd or mixed to the ADAU analog input.  This probably requires a receiver + DAC, so $$.

3.  Switch to an ADAU1442 or similar (adds $5), which handles the digital side nicely, but requires a codec to retain my analog capability, so that's another $2 or so.  The extra processing is nice but I don't really need it.

Given that this type of input is so common in inexpensive consumer gear, I'm surprised it's turning out to be so expensive - easily $5 plus the connector in quantity.

Any other options I'm overlooking?

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  • 48kHz does the job almost 100% of the time. I have not come across a situation where I could not get audio with SPDIF set to 48kHz.

    Kindly note that this statement is not backed by document/ specification but based on my experience.

    Others can share their experience as well.

    In fact, I feel that AD should re-release ADAV4601 as is but with added SPDIF decoder. It enjoys full SigmaStudio library support even today so no ground work will be needed there! It WILL be a BIG HIT!!

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  • 48kHz does the job almost 100% of the time. I have not come across a situation where I could not get audio with SPDIF set to 48kHz.

    Kindly note that this statement is not backed by document/ specification but based on my experience.

    Others can share their experience as well.

    In fact, I feel that AD should re-release ADAV4601 as is but with added SPDIF decoder. It enjoys full SigmaStudio library support even today so no ground work will be needed there! It WILL be a BIG HIT!!

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