The original question was converting PCM to DSD. I do not believe Sox does that conversion. There is nothing in the Source Forge documentation to indicate it does PCM to DSD conversion. It is quite a different process than PCM upsampling and downsampling.
When converting from DSD to PCM, MC first converts to PCM with a sample rate 1/8 of the original (e.g. 2.822 Mhz becomes 352KHz PCM) using open source code and if that is downsampled to, for example, 176 KHz, then that downsamplng from 352 KHz to 176 KHz should be done using Sox, if the Sox option is checked. The only way to know for sure if Sox is being used in that second conversion is to have one of the developers verify it. One option would be to do a conversion from DSD to, for example, 172 KHz and time how long it takes, with Sox and with the original algorithm. If they are repeatedly different times, that would indicate that Sox is being used if the box it checked. You might need a large file, or a whole album, to see the timing differences.
