I know it's not as easy to do this, but I think if you precisely level-matched the playback and cut back and forth between the DDC and non-DDC passages it would reveal more (if anything) about the differences. You're getting into subtle territory with a reclocker when you're already using a DAC with a quality clock.
I felt like WITH DDC was quieter. I felt like WITHOUT DDC the music was popping through some barrier or film. I think it is very high frequency electronic noise from the macbook, but i could be wrong.
I am in no way an expert. However, I will say that with the DDC, it had a smoother, cleaner, more detailed sound. Maybe a bit warmer too? Without the DDC, the sound seemed to be a bit harsh and grainy. I could tell a difference and I preferred with the DDC.
You might also compare (1) HDD -> Streamer -> DAC with (2) HDD -> laptop -> DDC -> DAC. One of the reviewer did report that they are quite even in sound quality. Also, did you use I2S connection in (2)?
I could hear no difference... And, I have the Iris DDC and the Ares II, new Node as a source, I don't know if it really makes a difference. I do know this, I cannot tell the difference between my CD transport and Node with the Ares II. Tracks from both streamer and CD, both sound identical. And I have tried this with multiple CDs and streams. I have the Denafrips Hades pre, Thallo amp, KLH Model 5 speakers. The CD transport is the Oppo BDP-83 using the GeerFab digital breakout box to pull the highest resolution possible out of the Oppo via HDMI, coax out to the Ares II.
I highly recommend the Pd Creative with lps upgrade on the node. I did it to mine and the improvement was significant. Bigger sound stage, tighter bass, more clarity.
Better without the DDC........sorry.......I have read the comments below........seems about 50/50 prefer/don't prefer the DDC. I downloaded the video to eliminate the pesky RU-vid compression and listened to the video over and over and over again trying to pick out detail on instruments and vocals. Listening on a $60K home system.......ProAc speakers, Mark Levinson amps, Lexicon environment surround, Acoustat and upscale B&W environmental speakers, from a Mac USB going through a Pontus II. Personally it is impossible for me to evaluate the male lead vocalist as his voice is so breathy it sounds like he's trying to have oral sex with the microphone. Finally I focused on the percussion in the background......almost hidden.....and the attack of the snare drum and the brush of the Hi-hat cymbal are much more precise without the DDC. Sorry.....no offense.