Looking for help understanding clock usage in my system

@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. 

@sls883  These are very good questions, and you’re far from the first to run into them. I found an instance where Gustard customer service provided clarification to this question, which was published in a Facebook post in a Gustard group. Relatively few DACs have a PLL, and some like the Holo Audio May enable this feature to be toggled on or off by the user, but not in your case.

This is not like in a recording studio, where everything is synchronized to the same clock. Assuming Gustard’s clarification is correct, it seems the only place in this system where the OCK-2 would be the master clock is with the N18 Pro. As for the U26, the OCK-2 should make no difference, but it’s free to try.