According to a Wolfson Engineer,

OSR, it's the DAC-to-input-rate-ratio. We want that to be high to have the DAC run fast, but not too fast to introduce timing related mayhem. You can't set this ratio directly but only indirectly through R7.Thus the OSR bits in the DAC controls the Internal upsampling of the DAC.

When you setlow ratewhat you tell the DSP ishigh OSR. It means we use the maximum amount of upsampling since we know the input rate is low enough such that the resulting DAC frequency lies in the sweet spot of performance: high to run the sigma/delta with loads of headroom, not too high so as to introduce analogue problems.

For medium and high rates, the actual upsamplingratioreduces such that with the higher input rates we end up with the same actual DACfrequency.

- Low rate means "apply highest internal upsampling"
- Medium rate means "apply medium internal upsampling"
- High rate means "do not apply any internal upsampling"

- If you input sample frequency to the DAC is 44.1 KHz, you can select any one of the 3 settings. With Low Rate, maximum internal upsampling is applied, with High Rate, no internal upsampling will be applied.
- If your input sample frequency to the DAC is 192 KHz, then you can only select High Rate, meaning that no internal upsampling can be applied because the input data is at high rate or has been upsampled outside of the DAC

## 4 comments:

Very interesting! I am implementing the arduino into my Opus setup much the same way you have done. You and your blog has been very helpful.

Daniel,

Thanks. Please share your implementation, and let me know of any improvements you make...

Yes of course. I'll get back to you when i'm ready.

What an interesting blog.

I am curious if it is possible to set the SRC to "unused"

with your software as listed above.

Post a Comment