Hello. I owned an SP-10 for 9 years (mid 80s to mid 90s). This was an awesome preamp for phono reproduction. When I finally bought a CD player, Pioneer PD65, the sound was ok but overall not musical. Was it partly the phono vs CD wars or was it also partly due to the SP-10's line stage? The answer was both.
I felt it was time to look into upgrading the SP-10 but as I quickly learned, ARC preamps are hit and miss. It seems like one really stands out from the crowd every 2 or 3 generations of ARC preamps. This is strange as ARC amps are continuously excellent. The SP-11 and SP-15 with all the rave reviews never did it for me in terms of musical enjoyment. The LS2 was absolutely terrible....way too analytical. Only when I sold the SP-10 did I realize what a gem this unit was when I was looking to get another preamp. Finally, the ARC LS5 was what I was looking for. This is a highly underrated preamp. But it's also a pain for those with anything other than all balanced components. But what this unit does is along the SP-10 qualities. This with the ARC PH2, has all that magical bloom and musicality of the SP-10 but with so much more resolution and extension at the frequency extremes the SP-10 could barely even hint of.
The Ref1 came out a couple years later, and then the LS5 MK III, followed which was a rework based on the REF1. I heard the LS5 III vs my MK II. Sonically they were nearly exact but the MK III had a more natural tonal balance on the top and yet even more resolution in the mids. Otherwise, they were so very close. And to my ears, as was the case with the ARC dealer, the LS5 III was preferred over the Ref1. The LS5 seemed to have that little bit more of warmth and seductiveness over the Ref1. And the Ref1 had a little more resolution. But these two models definitely have a sonic similarity. I have heard this view from so many other LS5 owners as well.
And by the way, concerning CD playback, it was so much improved with the LS5 over the SP-10. The SP-10 was an awesome piece for phono, but a very very poor choice for line-level components in my view.
I can not speak for what a hot-rodded SP-10 would sound like with all the latest cap and wire, etc., changes would do, but the stock SP-10 II is no match to the LS5/PH2 nor the Ref1 in either LP or CD playback.
And if you might think of other ARC preamps here, the LS15 and LS22 were not at all in the same league as the LS5 or Ref1. If you want that magical bloom and midrange magic of the SP-10, you won't find it in the 15 nor 22. An audition of these vs the LS5 indicated the 15 and 22 were not in the same league. These were again disappointing to me. ARC preamps clearly do not have a consistent sonic character from model to model. I have not heard the LS25 nor Ref2.
So if you are looking stricly for a line-stage preamp, the SP-10 really makes little to no sense. It's true magic lies in its phono playback. And even then, phono stages have come a long way since then.
Hopes this helps.
John
