Much less so than with a master clock using a faster acting PLL. It is my understanding that phase noise will skew the transient of the clock signal (the nice clean edge of the square wave) in the time domain, essentially meaning that phase noise causes jitter. As the phase noise, by definition, is random, it means that it will over time average out. Thus, the jitter introduced by the phase noise will average out.
Given that a dCS Master Clock has a slow acting PLL, it means the immediate short term variations in the incoming reference clock signal do not get passed on down the chain and affect the DAC as they would with a fast acting PLL. Furthermore, as the jitter from the reference clock is averaged out over time it doesn’t cause any longer term issues for the Master Clock (such as the DACs buffer overflowing or emptying causing a dropout in the audio).
If you had a fast acting PLL in the Master Clock, a reference clock with a phase noise of -115dB/Hz would cause less jitter in the Master Clock’s output than a reference clock with a phase noise of -110. In the case of feeding a reference clock into a dCS Master Clock however, the more important factors to look at will be absolute accuracy (jitter performance) of the reference clock.
It stands to show that for use in an audio system, a 10MHz clock will face challenges in terms of accuracy that a clock running at 22.5792MHz / 24.576MHz will not. It would seem counterintuitive to feed a Master Clock with a reference which is less accurate than the one in the Master Clock itself, as it will not be bringing anything to the table.
My suggestion is to look at the absolute accuracy of a clock to make a judgement on its suitability, and that inserting a 10MHz reference clock into a Vivaldi Clock simply because the input is available will not necessarily yield any benefits if the reference clock is not more accurate than that of the Vivaldi Clock (such as, as has been mentioned elsewhere on the forum, the much lower price point 10MHz clocks that tend to get a lot of traction on audiophile forums). Clocks with this level of accuracy do exist, but usually in satellite systems, telecoms and the like, typically with far more controlled environments than our listening rooms.