Using Gustard C18 master clock into RS130 via 50 ohm square wave connection with good results.
On good recordings the leading edges of notes, space and depth are superior to onboard clock to my ears. The midrange also seems more transparent highlighting more detail. The downside on poorer recordings it shows warts and all. The joy is with a button flick I can return to onboard clock or for a warmer presentation flick to the USB output and let the DAC to its asynchronous role bypassing both clocks. The joy of choice