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?
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!!