@timothy468 DDC's potential advantage comes from clocking and power supply to that clock in DDC vs internal clock and power supply in dac. In comparing clocks, general hierarchy is OXCO best, followed by TXCO, then Femto. And then we have to consider power supplies to those clocks, this extremely important as well, with superior power supply it may be possible for Femto clock with very nice power supply to outperform OXCO clock with lesser power supply. Also, not all clocks created equal, therefore, they all vary in quality. Finally, length of I2S cable needs to be shortest possible, 1/2M at most, I2S clocks provide highest performance when located closest to data path in dac, having to travel along cables messes with timing to some extent.
Input quality also variable with DDC, do your research prior to purchase. The quality/optimization of this interface also important, when thinking about streaming one has to consider entire chain.
So, I have Harmony dac, use Denafrips Gaia, chose this for it's extremely high quality OXCO clock and power supply, also very nice input design. This relatively high price for ddc, I chose this since I wanted to hear full potential of going I2S, same reasoning for choice of Tubulus I2S cable.
Since your looking for a streamer I can see the sense of going with streamer with I2S output. Still need to research quality of that output, you could avoid need for DDC altogether if quality high, otherwise not worth limiting your choice of streamers to those with I2S output. As for my particular setup with Harmony, I2S superior vs my optimized usb, the usb board in Harmony is pedestrian, nothing special, high quality I2S setup should sound best vs usb in this dac.
