DACs, external clocks, and what's what

@phusis I don't doubt for a minute that your external clock has resulted in improvement-its foolish to question what someone else hears. That's not really the question that is at the crux of the debate that interests me. I think the designers like Meitner and the MSB guys-certainly well credentialed-would say that IF the internal clock is designed and built to a certain standard the external clock is unnecessary. In fact, I think Meitner has suggested the external clocks are "stupid." Of course, the opposite is true if the internal clock is not optimized.

On the other hand, equally well credentialed designers such as dcs, Wadax and others take a completely different view. So, the fundamental difference in design philosophy is not whether an external clock makes a difference in a particular application, but whether buying that extra box can be made unnecessary by designing the internal clock to a higher standard, which, of course, is less costly than putting the clock in an extra box.  As I said, I don't know who is right but simple logic dictates that both sides can't be right. That is uncomfortable for some, but an important question for dac shoppers.

The dac market is interesting. You have this choice, the topology choices-chip, R2R, etc, then the NOS/filterless trend-its confusing. And it seems that new dacs are hitting the market every day. Sounds like your solution works well for you which is really all that matters.

Engineering expertise ≠ unbiased opinion.
Both sides have valid advantages and disadvantages. While there are advantages to design a one box A-Z solution, there are also advantages to building separate components to optimize/update each separately to plug into a digital solution. There is no right or wrong, only the engineer’s design preference. 

There is only 1 truth is false. There is a substantial market for both.

If having “options” make you “feel” like there’s something missing or that your DAC is somehow “feeling subpar”, then it’s you, not the DAC. Usually options vs none is considered good - having additional opportunities to upgrade Sonics is better than none. If you cannot get past this emotional baggage, maybe options is not a good choice for you.

@kerrybh  I think the designers like Meitner and the MSB guys-certainly well credentialed-would say that IF the internal clock is designed and built to a certain standard the external clock is unnecessary.

This is correct in principle, but achieving "a certain standard" in practice and replicating that within the confines of a DAC can be challenging depending upon one's definition of "a certain standard." It's not a matter of who's right or wrong, but what degree of clock performance one determines to be good enough.

@kerrybh ...but whether buying that extra box can be made unnecessary by designing the internal clock to a higher standard...

Clock platforms are highly sensitive to various electronic and environmental disturbances. If we consider an external clock with extremely good phase noise performance (e.g. MUTEC Ref10), it achieves this in part by having its own isolated power supply, regulation, electronic architecture, and chassis that it shares with nothing else. Attempting to fit this standalone unit into the confines of a DAC while maintaining the same level of performance would be challenging, not unlike attempting to squeeze an upmarket standalone DAC into the confines of an integrated amplifier while maintaining its expected performance. 

What degree of audible difference (if any) an external clock may bring is dependent upon a host of variables and the perceived audible difference is subjective. What isn't subjective however, is reputable clock producers will provide actual phase noise measurements taken at the output, and phase noise @ 1-10 Hz is a direct indicator of clock quality and precision regardless of all else (including price). 

@OP. Designers have different approaches and philosophies so wondering about "if one is right then the other must be wrong" is a fruitless task. External clocking largely arose for two reasons: it originated in studios which needed to synchronise a disparate set of digital outboard to a common clock (as you reference in your post). In domestic hi fi, the need was driven by ensuring that transports and DACs were clocked to one another as accurately as possible. However, that is not to negate the philosophy of using as accurate and low phase noise a clock as possible as a reference for the PLL - as per the Grimm paper. Also, as you rightly say, the Wadax Studio Player sounds really excellent without an external clock, indicating that it's internal clocking design is of high quality. I have yet to test the player with the Wadax clock, which by the way, uses a different schema to DCS's or the various 10 Mhz clocks on the market. However, from experience with Esoteric equipment, I can hear clear improvements from using a high quality clock. But I have also auditioned some of the cheaper clocks and found them to either make no improvement or even disimprove the sound. 

An external clock may change the sound, but "better" is arguable.  The physical distance from the DAC chip increases jitter.  Ideally, the best jitter performance would be with a clock chip physically adjacent to the DAC chip itself.  

It's worth pointing out that in the 21st century, affordable clock chips with vanishingly low errors became common.  Also, an atomic style clock may have very good long term stability (great for a wall clock in space) but poor sample to sample error.