“Q: Does the device support MQA over the coaxial or optical input?
A: No, in order to enable MQA playback via S/PDIF a hardware change would be necessary, this would cause the price to go much higher. MQA hardware decoding is only possible via the asynchronuous USB input of Pre Box S2 Digital. ”
http://www.box-designs.com/main.php?prod=preboxs2digital&cat=default&lang=en