@debjit_g Very interesting. Assuming you have atx board, why don't you try Pink Faun I2S board to compare with Jcat usb?
Having mentioned many times throughout this thread my curiosity and assumption atx board servers may be SOTA, perhaps I should mention I do in fact have relatively high end diy custom atx motherboard computer in house. I built this five or six years ago, relatively high level AMD processor, liquid cooling, gamer motherboard, high end graphics, improved motherboard audio all in giant case. This was real exercise in excess, built for the fun of it. I've thought about converting to music server only duty from time to time, but power supply mods ($2-5K), cards themselves (each one $400-2.5K) and time and effort to install hardware, optimize software, OS may not be worth it for build that started as general service computer. The AMD processor may be overkill, no dsp for me, and faster processors make more noise, liquid cooling inferior to passive air for audio duty because of noise and power supply demands, also, the motherboard isn't inherently best for music server duty. So, bottom line, I'd be able to try great rendering with Pink Faun and JCAT cards, but within context of less than SOTA atx build.
Hearing your less than satisfactory results using external DDC kind of confirms my presumption Singxer SU6 would be inferior to my usb setup. This was initially confirmed to some extent by observation of some modifying the SU6 with external power supplies, this despite having supercap PS which Alan at Vinshine claimed didn't benefit from lps. I also saw further mods to, can't recall if it was voltage regulator, caps? All this confirmed inherent issues with even higher grade DDC, they need to be top grade to optimize I2S.
@melm I totally agree with you, between the engineering of that board, and sound quality, both initially, and continuing, I should have absolutely no motivation to even try the I2S scheme. But then would I really be an audiophile if I wasn't at least curious! And this the reason for all my atx server curiosity.
I suppose all my streaming upgrade plans are based on wanting to hear full resolving capabilities of 005. This damn dac just wants to lead me down this path where everything feeding it needs to be SOTA. I've never had a source like this prior to 005, prior vinyl and digital source resolving limitations have been exposed for perhaps last ten years or so by the rest of my system or systems.