Digital clock - any recommendations?

For that unit you'll need a clock that outputs 44.1, 88.2, and 176.4. Try an Antelope LiveClock and upgrade its wall wart to a good LPS.  If you want to go further, the LiveClock may in turn be synchronized to a 10mhz atomic clock like Mutec, Cybershaft, or Stanford Research System.   

The most affordable
https://www.m2techusa.com/collections/frontpage/products/evo-clock-precision-clock-generator
you must buy an highend  BNC cable
 How cost the Esoteric  compare to your Marantz ?
May be with Marantz , the difference will be subtile

This difference may:
1- not be better2- is very DAC dependent.
From an electrical engineering point of view, you want the clock as physically close to the DAC for the best signal and lowest jitter.

I prefer to get a DAC with a great internal clock, Mytek. Anything outside the case is going to be worse just due to the distance involved.


I suggest you audition your DAC and keep an open mind as to which version sounds better.


Best,

E

How much are you willing to spend?

Any excellent DAC will not benefit from an external clock. The good ones, like the Benchmark DAC3 reclock S/PDIF themselves, so the only jitter is internal.

Why buy a $700 reclocker when you can get $700 or cheaper DAC with external jitter reduction?

For instance, the Schiit Modi 2 showed improvement when the Empirical Audio $700 reclocker was added, but pretty much no difference when used with the Topping DX7s ($500 DAC+headphone amp).

Going digital out of your Marantz to say the SMSL SU-8 would give you similar results to using an external reclocker, in that the jitter from both would be well below audible levels.

Any excellent DAC will not benefit from an external clock.

Did you not read the OP? Presumably Esoteric make good DACs with good clocks? dCS also have an adequate reputation yet my Vivaldi stack improved significantly with the addition of the Mutec 10MHz clock.

Besides the performance of the clock having a separate and dedicated power supply and greater isolation from vibration can all help - in my experience in addition to care in choice of the BNC one also should pay attention to footers, power cord and grounding