It's not easy to take such a review of the SP11 vs Ref1 very serious based on my ownership of some ARC preamps over the last 15 years. I owned an SP10 Mk II for 8 years and just loved it. It had poor frequency extreme extension on both ends, it had mediocre resolution due to noise and it had a terrible line stage for CD playback. But for LP playback, it had a most incredible musical presentation of midrange bloom and 3D that no other preamp at the time could match.
With all the faults, the SP10 was a musical product. I did hear the SP11, and yes it had some refinements over the comments above, but the SP10 was preferable to me for sheer musical involvement.
After listening to numerous preamps during that time, I finally heard the LS5/PH2 combination. For the first time ever, an ARC preamp came along that brought back all the SP10's magic but with a new level of refinements that finally made it clear how dated the SP10 had become. The SP10's ambience and bloom was there and so was a wealth of information never heard before on my LPs...both in the bass and treble. And gone was that very high noise floor.
I have since heard the later versions of the LS5 and the Ref1 (I prefer the LS5) but still I know the Ref1 is miles ahead of the SP10 as a line stage. I have a hard time believing the SP11 trounced the Ref1 in all areas. Any time I compare two products, it is very rare that one product takes the show from another in all categories. The Ref1 like the LS5 and later preamps has far more resolution than the older SP series could ever have.
If the rest of the system is not up to the latest preamps, then its strengths would probably not be very obvious. Without knowing the context of the rest of the system for which these 2 preamps were compared, the blanket statement, "the ARC SP-11 MkII outperformed the ARC Ref. 1 in every ways." has very little meaning to the readers of this forum. What was the source?....what was the interconnect from preamp to amp, what was the amp.....etc?
I do agree that the LS1, LS2, LS3, LS15, LS22, do not have the SP10 or SP11 magic. And yes the SP10 and SP11 were phenomenol products at their time, but today, they are simply no match to some of the later preamps such as the LS5 & Ref1. I can only assume the LS25 and Ref2 MK II versions go yet another level.