What did a good 10 MHz clock do for your Gustard R26?

"When you run the clock cable to the DDC on Ext Ref and then I2S from DDC to DAC, the 10Mhz clock signal is supplied to the DAC via the I2S signal. There is no need to run another clock feed as external reference for the DAC. In this case, the DAC clock should be set to Internal. When used in this fashion with I2S It is redundant to run separate 10 Mhz clocks to both the DDC and the DAC. Saves the cost of an additional clock cable."

I'm not super knowledgeable about some of these connections and need a little help - I'm using a Gustard x26 Pro.  I began by using the USB input.  My first upgrade was to use a cheap Douk Audio DDC with a decent LPS so I could use the I2S input in the DAC.  This was an improvement for me.  My next upgrade was an Afterdark external clock.  This was another improvement.  Now I'm reading the above post and I'm looking at a Gustard U18 DDC.  Looking at the back panel of the U18 there is a BNC connector marked as an input "1OMCLK".  There is also a BNC output marked "WCK".  If I understand the post, I can use my Afterdark clock with the DDC and then simply use an HDMI connection to the DAC and I will get the benefit of using the external clock with the DAC as well.  Is this correct?  Thanks for any help.

@audphile1 

While I do recognize that my system might have some kind of "signature" as a whole that is obscuring these components, I've had a very good experience with Igor's mods. I started with just his power conditioning (but all stock components at the time). It made my system more extended on top and more musical by quite a lot. In particular it made things more extended by not brighter. Everything he's done since has built on that. I've carried some of his modified components to other people's systems and they bring similar qualities. Like, a long time ago when I still used CD I brought his modified PS Audio Lambda II to a friend's system and it improved the extension without making the system brighter. I've been in contact with folks in the New Jersey Audiophile Society who use his cables rather than the $5000 cables they could easily afford. He mainly takes moderate priced equipment and brings out the potential - so for instance my headphone amp is a Chinese 12AU7/FET zero-feedback design that comes with a SMPS ($100 new!). He replaced all the parts, added shielding through ERS fabric, added damping, and designed a LPS. Many people in the headphone community praise the concept of 12AY7/FET designs, so it's not surprising how good it is.

With the PS Audio DAC, I'm feeding that by a stock Aurender through Igor's USB cable. Tell you what, I'll replace that with a stock USB cable and test it. Then everything will be stock components except the headphone amp. I'll try it with several headphones through their stock cables. Let's see if it changes the tonal balance or component signature.

@magon actually not a bad idea! I always go back to stock cables to set a baseline for a component’s sound when evaluating it. Aurender includes a very nice usb cable if you still have it, worth a try. Or just use any basic usb and power cord. 
Awaiting your updates. 

Looking at the back panel of the U18 there is a BNC connector marked as an input "1OMCLK".  There is also a BNC output marked "WCK".  If I understand the post, I can use my Afterdark clock with the DDC and then simply use an HDMI connection to the DAC and I will get the benefit of using the external clock with the DAC as well.  Is this correct? 

Yes, correct - Just make sure the DDC is set to External Clock and the DAC clock reference is set to Internal when using the I2S input.

Thank you, dspringham