In re to MikeB’s and other comments:
Amplifiers I have used in the last 20 yers or so with Sound Labs M-2 and M-1/M-1PX speakers: Balanced Audio Technology (BAT) VK-1000 monoblocks did not have enough power to drive speakers. Pass Labs X600.5 mono block amps were ideal. Sanders Magtech Stereo Amp was also very good but not as smooth as the Pass amps. Finally, replaced with Pass Labs X600.8 and Atma-Sphere MA-1 monoblocks – both sounded beautiful and had plenty of power with headroom to drive Sound Labs speakers.
Pre-Amplifiers I have used in the last 20 yers or so with Sound Labs M-2 and M-1/M-1PX speakers: Pass Labs XO.2 and Pass Labs XP-30, both sounded very neutral without coloration, however, both were very bland (blah … the music lacked authority and excitement, i.e., almost boring). Meitner/EMM preamp PRE-2 and Atma-Sphere preamp MP-1 were excellent and enjoyable replacements.
In these set-ups, I always had stereo REL subwoofers of various types over the years, all of which added to the soundstage.
I upgraded in 2017 to the Sound Lab Ultimates U1-PX (Ultimate 745) and have the updated backplates. These have been excellent with SS (preamps PRE-2 or PRE by Meitner/EMM and PassLabs X600.8 monoblocks) or Tubes (Atma-Sphere preamp MP-1 and Atma-Sphere MA-1 pair of monoblocks) in conjunction with stereo REL G-1 subwoofers.
Sources are either Basis 2001 Signature Series Turntable (via Atma-Sphere MP-1), SACD/CD player TX2 by EMM, DA-2 DAC by EMM, or digital files on a Mac Mini using Audirvana software.
In reply to MikeB’s specific question: I do not do A-B comparisons, song by song, track by track as it is cumbersome (a fragmented back-and-forth mental and audiovisual exercise). However, every 4 weeks or so I switch between the SS and Tube components while continuing to hear varied music I was into the prior 4 weeks or so in order to have a concentrated and wide comparison. There is no clear winner in this type of “back-to-back” contest – both are very revealing, the SS is slightly better in this aspect. However, as is well known, the Tubes sound warmer and more bass heavy than SS; thus I have to reduce the bass setting on the backplate by 1 when I listen to Tubes.
All I can say is music seems “New” or “Have I even heard that song that way before” when switching from SS to Tubes or vice versa. Bulls-eyes are hit on slightly different targets by both, so there is no clear winner. Hats-Off to the individuals and companies that provide such products.