On the most recent USB port it is possible to transfer DSD digital audio data. DSD is the digital audio coding used for the SACD format. On a USB we can transfer DSD, DSDx2, DSDx4 so data at a speed like the one of a SACD but also at two or four times fast so with higher resolution. There are two ways to transfer DSD, DoP and Native.
The USB port itself can’ t recognize if a data packet is DSD without a dedicated driver. Without a driver all the digital audio data on the USB port are seen as PCM data. So a way to trasmit DSD data on a USB connection without a driver is to package the DSD data in PCM form. Be clear: this is NOT a data conversion from DSD to PCM. The data are unchanged. But in this way the USB port can’ t understand that this is a DSD stream. To solve this problem it is necessary to add at the DSD data a particular code. When the DSD data incapsulated in a PCM format arrive at the USB receiver, the port itself recognize the code, understand that the data are DSD and discard the code from the incoming data. In this way the DSD data is reconstructed perfectly at the USB receiver. The only disadvantage is to double the data rate since we need to transmit continuosly also the particular code. So for this reason the DoP on our implementation is limited to DSDx2 (5,6Mbit/s).
The DSD native transmission need an ASIO driver that communicate the start of a DSD stream. In this way is not more necessary to add a code and it is possible to push at DSDx4 (11,2Mbit/s) the DSD data rate.
So is not a question of quality. The DoP have the big advantage to use the PCM transmission so don’ t need driver oa a OSx or Linux computer. The limit is the maximum transmission speed. On the other hand the native DSD transmission push the speed beyondbut need a driver.