Looking for help understanding clock usage in my system

I suspect that by using USB into your DAC, the DAC is now in charge of the clocking.

Generally with AES (or coax)  connection from streamer to DAC the streamer is controlling the clocking.  With USB into the DAC the DAC is holding the clocking.  So in your description, I do not know if all that pre DAC clocking is as helpful as using the clock on a DAC that accepts a clock cable.  Of course an external clock may or may not be as good or better than an internal clock, but has the advantages of a separate housing and separate power supply.

@fastfreight To clarify, the OP uses USB into the DDC and I2S from DDC into the DAC, and therefore all clocking duties are performed by the DDC. I think the way it was worded may have been just a little confusing perhaps.

@sls883  According to Gustard, the X30’s external clock input is active only when the DAC is receiving a signal via USB or LAN. For all other inputs (I2S, SPDIF, AES EBU), the X30 has a PLL that reclocks the data using its own internal clocks. The only time the PLL is disabled is when using NOS PCM or direct DSD. If you are not using either NOS mode or direct DSD, you should find the connection between clock and DAC superfluous. Of course, with the X30’s PLL reclocking incoming data, it remains in question that a DDC (and external clock) provides any clocking benefit at all. Gustard’s customer service admits this. In that case, the primary advantage of the DDC would be galvanic USB isolation.

The OCK-2 is a nice unit for the money, and I had the upgraded OCK-2S until recently. It has been pointed out elsewhere that the square wave converter in these clocks is a primitive circuit and not on par with more expensive studio clocks (e.g. Mutec). I see you prefer that setting, but most find it sounding "edgy" as compared to sine wave (just FYI).

Thanks for clarifying @ted_b !  

Truly, I don't get the purpose / benefits of a DDC.  Please explain if you will!

Truly, I don’t get the purpose / benefits of a DDC.  Please explain if you will!

@fastfreight The purpose of a DDC like the Gustard U26 is to effectively elevate digital signal quality/integrity by isolating, regenerating, and clocking the digital signal. To achieve this, better DDCs have their own low-noise power supply, isolation circuit, digital converter, and low phase noise clocking platform. 

Removing galvanic source noise and converting the signal to a synchronous digital format that is locally clocked by the DDC minimizes the influence of both source and DAC on signal quality. As such, a good DDC can effectively improve the perceived performance of various source components and DACs.

@fastfreight @ted_b Thank you for the responses!

I'm inclined to try the U26 without the external clock.  It is a considerable step up from the U18.  Maybe the clock is of no benefit with it.

I simply hooked the ock-2 clock to everything with a clock input with the notion that everything should be clocked the same.  Just because I don't understand it.  As you mentioned, the clock to dac is not doing anything with i2S (I didn't know this). 

I had read that the square wave output of the ock-2 was edgy sounding to some people, but I didn't think so. 

Would there be any benefit to hooking the ock-2 to the N18 Pro ethernet switch if I'm not using the ock-2 for anything else? 

Sorry for all of the stupid questions.