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

The overall tone of this thread reads like a warning to me. The OP is trying out a second unit because the first sounded dark and broken. Now the second unit the  imaging collapses and the highest octave is soft. I also read several other posters have added modifications to their R26s from clocks to cables in order to achieve the desired performance level. Clocks can add $750 up to $5500 to a $1700 component. I wish you luck in this pursuit. I also believe you and others will be successful due to your knowledge and dedication and obvious discerning audio talent. This one is not for me, my budget is more like spend $1700 but don't take chances @jolywins 

After having issues with the second unit if it was me I’d absolutely cut bait and move on as there are so many other excellent DACs out there.  The Denafrips Pontus jumps to mind, and adding their Iris DDC at some point will give you the ability to take advantage of its i2S connection and get a significant performance boost for not much more $$$ especially if you buy used (that’s what I did).  Just my $0.02 FWIW.

Found the best solution for my R26 was Gustard C-18 clock output to U18 DDC (set to Ext. Reference). Use good quality coax cable here. Experiment with square wave vs sine wave clock output. Sine wave output is less sensitive to cable impedance (U18 clock input is 50 ohm - make sure to use equivalent impedance cable if using square wave output). 

U18 is fed USB from server (in my case Antipodes K30). R26 gets the I2S output from U18 (make sure R26 is set to Int. Ref for clock). I2S cable supplies data and 10M externally referenced clock signal from U18. Once again -  a high quality !2S cable is important (Tubulus for me).

Sounds great to me. In this setup I believe the overall quality of the server is of greater importance and contributes more to the sound quality than the dac. I'm feeding the U18 with upsampled PCM (via PGGB - files served from internal SSD on the K30) at 705/768 kHz/32 bit. The R26 is set to NOS mode.

Dave

For the sake of argument, since I basically have a similar system as dspringham in above post, but unlike him I keep the dac on ext clock which provides a wider more expanded sound than using the int clock. I am of the school that thinks the entire chain gains from being on the same master clock, even I2s. At least it is true to my ears in this system.

For the sake of argument, since I basically have a similar system as dspringham in above post, but unlike him I keep the dac on ext clock which provides a wider more expanded sound than using the int clock. I am of the school that thinks the entire chain gains from being on the same master clock, even I2s. At least it is true to my ears in this system.

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.