"SQ" I think we've been using on this thread to mean "sound quality."

I have a hard time figuring out what the Grid Mod does to the sound as I don't have a control for comparison. I have two Torris with the mod, and two other EL34 amps (Integrated and SE34 Monoblocks) without them. They sound different, but then two are Push Pull and two are Single Ended as well, so many variables.

Still seems to me that the mod is an amazing improvement that makes a big difference. But like will, I hear clear differences in the "signature" of power tubes in the Torii.  I've been very familiar with Winged Cs, and when I've had "Svetlana" tubes in it clearly has a different sound, and when I have had cryo'd Tungsol reissue tubes in they also sound differently. (I use the Tungsol reissues in my Torii Mk II predominantly; I prefer the Winged Cs in my Mk III.)

I have the impression that tube changes have an even bigger effect in the Integrated. When I change any tubes there, input, output, rectifier, there is a strong influence on the total sound output. I use cryo'd Mullard reissue output tubes there, I really like those; at some point I may try a quartet in the Mk III. Not sure if that is because there is no Grid Mod, or the fact that it's an even simpler circuit, or just my imagination. Anyway, I'm really enjoying the Integrated currently in my second system, where I don't need the power of the Torii amp. There's something about the SET "sound". . . not as precise as the Torii, but with just a touch of romance.

Hmmm. . . probably serves me better then without the Mod; I actually think it works very well with most recordings this way. Especially those my girlfriend loves to listen to, I've learned to like the music, but not the more mainstream pop production and recorded sound. Still, the Integrated manages to bring out a lot from Marc Anthony and Andres Bocelli cds.