Does your DAC sound better through the S/PDIF or I2S inputs than through USB?

@rbstehno 

My server is an Aurender N100 and has only USB output. I’ve tried two different DDC’s in order to convert to I2S or SPDIF for my Gustard R26 DAC and the better one is the Gustard U18. (I haven't tried the Iris 12th or other DDCs so I'm not sure how the U18 compares.) I’ve tried the coaxial connection and the HDMI connection. Coaxial sounds best. The I2S through HDMI sounds a bit bright and more sterile.

My HDMI cable is a 0.75 M Audioquest Firebird, a $1600 new cable although it comes up frequently on US Audio Mart for much less than that. My coaxial cable is a custom silver, highly shielded cable made by Igor Kuznetsoff, which is likely better quality that my Firebird.

Most dacs these days are designed to be connected to a pc using the usb standard printer connection for it’s more robust and less likely to break. So if i2s and usb support the same format which usb use to be higher but on the smsl sux dac and the topping centerious they both sound good with usb or i2s, but I am using i2s and it sounds pretty decent, audio is best with xlr, usb, and i2s those should be the only connections available especially to bring prices down on overpriced audio equipment that doesn’t even measure well and ones that go beyond human hearing are nothing but a waste a few kilohertz higher sure but not double for there is no use for it 

my dac Ideon audio Ion sounds awsome   over USB.  They have killed usb hum , it is almost equal to I2S.

The salient point using I2S vs all the others is the ability to use a better clock via a DDC vs dac's internal clock. With superior clocking presentation can be greatly affected. Proper clocking means data packets more correctly timed which results in a much more analog like presentation. If you investigate most dac's internal clock you'll generally find Femto clocks with rather pedestrian power supplies to those clocks, one can do better in this case. Not sure I'd want to purchase any dac devoid of I2S input, minimally I'd want to compare my Denafrips Gaia with Tubulus Ximius I2S cable to the dac's internal I2S architecture and/or it's usb implementation. The only higher level dac I know of that incorporates I2S is the Mola Mola Tambaqui.

PS Audio also incorporates I2S inputs in their Stellar Gold and PureWave DACs.

I use the Tubulus Concentus I2S v.2 cable between my Jay's transport and PS Audio StellarGold DAC. Sublime!