Well, I have some listening time in with the ARC LS26 and M1's, and it is a great sounding combo! This particular LS26 has the BAT tubes installed, nearly new. The LS26 and VTSP-1a/166 actually are pretty similar in terms of presentation, with the LS26 maybe just a little more forward and with a brighter presentation. The LS26 definitely has more background detail on complex recordings (orchestra) but for vocals and jazz, they were very similar sounding. Even hearing very familiar recordings (such as Kind of Blue) I had trouble really distinguishing them. The LS26 seems to be quite neutral, and really lets the instrument come through naturally. Separation between instruments is excellent, tonally they seem very natural, pace is great, and the LS26 really controls bass well. The best pre I have heard in my system.
Overall, in comparison to the Herron 1a/166, the LS26 has more background detail, and perhaps more detail is heard in the recording. The Herron seems a tad more natural, the LS26 a tad more forward (maybe some instruments come across as slightly hi-fi). Mainly, the increase in background detail is the big difference, with perhaps a bit more air under more complex passages, and slightly better separation. They are very close in terms of performance though: more than you would expect, considering that the LS26 is 2x the price (used) of the Herron. If the LS26 is a $4000 unit, then the Herron sounds like a $3000 unit: the differences are there, but they aren't huge. Considering the LS26 is a current unit and the 1a/166 a 7-year old model, then the newest VTSP-3 is likely superb. After auditioning the LS26, I will hold off and wait for a VTSP-2 or 3.
