I generally will always go with SOS and I agree here we are talking about the smallest of differences in possible sound quality. There are so many variables, it's not just external or not external clocking. And, it's not just the clock stage that influences what people and most engineers hear with higher end clocks (external or in their high end AD or AD/DA) it's the audio stages and how well those are designed which is not a function of price, but in some cases there are some really well regarded mixing engineers who are hearing something that is not something that is just altering the sound from neutral. Neutral or truth of what was intended originally recorded and hearing that (if you can - if you are in a room, with monitoring that allows such clarity) is the goal. It's commonly words like "opening" and getting ever closer to the holy grail of finally truly feeling like you are in the room with an artist or singer, they are with you right there. And in the production process not letting all the little bits along the way that can stamp that out. That's the difference between the numbers and testing and the process of creation. And why some guys are buying an Antelope 10m and after decades of thinking they were at the holy grail, they plug that into their rig, and it blows their minds. Again, in that neutral has truly begun to raise it's head lifting that last bit of darkness from the monitors you wouldn't have even known was there.
But, jitter I think once you are down to this spec:
"The reference clock of the Cranesong Solaris has less than 1ps (picosecond) jitter and employs a proprietary re-construction filter for accurate time domain response."
"The jitter measured for the clock, between our auditory spectrum of 10Hz - 20kHz, is typically around 0.045ps (44fs, femtoseconds)!"
Those quotes per Dave Hill at Cranesong with his evolution of his work with clocking is I think the most trustable from my standpoint around clocking and converters etc. And, the discussion isn't about anything with the clocking, it's what is surrounding it - design going in and coming out that truly is what people are hearing when they think they hear a difference.
I just got a Grace m900 for $499 and it uses a similar ADK chip as what Dave is using, I think those chips maybe are like $40-60 a piece - and in a $3000 converter or straight clock - that is hardly what makes the difference. These folks are incredible designers - the m900 to me I love because I know I can trust those Grace guys. And I know in both cases of these companies, they aren't mega corporations pushing next batch of new products to buy every year. Dave worked for decade(s) to get and refine his designs. And in pro audio I think that is what we want, to trust there isn't more to be gotten.
I am bias with Cranesong as I have Dave's amazing Hedd converter ((a $2000-3000 box) and the prior generation, just updated after years and years) which he would say, use it's clock, use it's converters, you don't need anything else. Yet, I still think no you need more gear, more-better expensive clocking etc. You need a Rubidium clock and an Antelope 10mx, but it gets to be basically a crazy pursuit. Again, I trust what some mixing guy is doing if he is putting out huge records like Havana and saying the secret to the warmth and mids is his 10mx. He is lucid, he is not on drugs. It's a tough call, but there is no way anyone or even the SOS article can just generalize.
I keep A/B'ing like the Grace m900 with it's ADK chip and Grace design standards to my 2005 Pioneer DV-563A for the DAC side of this equation, which has a Burr Brown DAC chip literally now well over a decade old. And on very basic average active monitors I can hear differences, but that Brown Burr chip and whatever Pioneer over spec'ed in these units that got discontinued because they had too much bang for the price of like $250, completely stands up and compares. Tiny bits of less mid-range smearing and just more of a FEELING of more power coming through and separation in the low end is what I hear with a modest but more modern DAC design, and not breaking the bank at all. And no clocking external wise at all in play.
The stuff really amazes me. Sorry, to dump like this
I was away for a bit and missed the tail end of this discussion.
Really glad you cited that SOS article though.
best,
Dayz