thank you for reply but goal is to use several external high quality stereo DACs.
Alternative is to use Lynx AES16 card but i heard in several places USB converters works better..
The problem with using multiple USB stereo DACs is that it's very challenging to keep them in sync. DACs won't generally stay synced unless they have a way of accepting an external clock (SPDIF, etc.). Most USB DACs are either asynchronous (meaning they use their own clock and ignore timing information from outside) or use an adaptive timing interface which only loosely couples the DACs output to the USB clock to reduce jitter. In either of those two cases, two DACs will not sync up, and in my own experiments with two identical DACs, they will tend to slowly drift apart while music is playing.
If you want to use two or more external DACs, you need to make sure that they have hardware support to sync all of them to each other (master slave) or the PC (either through SPDIF, or word clock, or something else). In my experience, many DACs do not support external syncing, or if they do, they do so only through a SPDIF input, which would make it hard to "daisy chain" more than one additional stereo DAC unless you have lots of SPDIF outputs. There may be a software solution at some point, but I'm unaware of anyone who managed to successfully do this with more than one USB interface without finding a hardware level solution to syncing the cards (i.e. feeding the second card off of an SPDIF output of the first card, rather than USB, etc.).
See this thread for a more detailed discussion:
http://yabb.jriver.com/interact/index.php?topic=79067.0
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Topic: using several USB DACs (Read 8537 times)