I own a B7 with the R2R PCM board upgrades, but not the superclocks. And a friend has the SS Atlantic and brought it over once about a year ago. Here was the system configuration during that comparison:
microRendu > Uptone hard USB adapter > Big7 w/VC > Tortuga passive VC, Hattor passive VC > Line Magnetic 518 amp > Daedalus DA-RMa V2 speakers
This was only a few months after my moving to a new house with a VERY different listening room than before, though. And I hadn't dialed in the system fully yet, especially regarding tube synergies. My highest quality tubes for the Lampi are the Takatsuki 300B's, but I've played with Psvane WE101D's, and KR/Lampi Aniversary 45's too. And a few rectifier options too. The Line Magnetic amp has Psvane WE845's, 1957 metal base 5AR4 recti, and vintage EI 12ax7's, new production Gold Lion KT88's.
Ok, we were all very curious about this comparison with Atlantic. Basically, they were very very close. The linearity of the Atlantic was most excellent - very balanced all the way around - warm, but also dynamic. Really nice DAC. The Big 7 with the Tak 300B's was sounding too dense/lush to the point of being a bit tubby in comparison. I swapped in the Psvane WE101D's, and got a very similar linear sound signature compared with the Atlantic, and we all liked this config. HOWEVER (WARNING) I screwed up and had the 101D's playing in the wrong setting - the one for 300B's! So it was being way overheated. I only realized this a day later. And when I put it back to correct setting - sound became much thinner and not a good synergy anymore.
But, during the audition, I think we were able to find some tracks where the Big7 pulled ahead, but it took careful listening and the right quality recordings.
That said, I have since been able to dial the system in a LOT more substantially, and the 300B's are no longer tubby. Main contributions are really stepping up refinement through power supply improvements in the digital supply chain. But also adding active tube preamp into the system rather than the passive options from before. I now have a Don Sachs pre with all the latest upgrades as well, Michael.
With these refinements and perceived SQ improvements over the past year, I'd really like to do the comparison again. It's possible they'd hang together again, but it's also possible that the more refined source would allow the Big7 to pull substantially ahead. I hope to try it again someday.