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I had a chance to compare an RP7 to an ARC Ref 6, then I learned a little about the difference between the 6H30 and 12au7. The former is going to have higher transconductance - there’s supporting discussion on the technical side if you search it. I did feel that the Ref 6 resolved better, however in my system the RP7 sounded smoother in the highs - but not as resolving in the highs, and more fleshed out in the lower midrange and upper bass, but lacked the low bass power of the Ref 6 - the Ref 6, like the Ref 10 is much larger and packs beefier power supplies. Perhaps the Ref 6 was more accurate, but I preferred the RP7 overall. So if Rogue keeps the smooth character of the 7 in the probably more refined 9, it should be very competitive with more expensive options, but I wouldn’t expect the low end you get from the ARC models.
Talked to Mark the owner of Rogue Audio. He said the RP-9 is build for the Russian 6H30P tubes with some different, more expensive parts. He did not quantify the improvement over RP-7. You could upgrade RP-7 to RP-9 for about $3K (with a different circuit board etc.). The real questions for me are (1) how much improvement over RP-7 and (2) how it compares with other pre-amps of similar prices (say $7K-10K). In my experience, may not be worthwhile to upgrade (e.g., I upgraded Schiit Yggy DAC to Analog 2 - but sold it at a loss when I compared the upgraded DAC to Metrum Adagio - the latter is much better).