It's thread resurrection time! I had not been happy with the tone of my amph for a little while so I decided to pull out the 5751 and replace it with the extra 12AX7 I bought at the time. I like it better now, although I can't necessarily quantify why. I went back and forth between the two with my two guitars at various levels of gain. The 12AX7 just sounded better to me. I'll keep the 5751 around for future reference.

One of the reasons that I wanted to try the 5751 was to see if it would give the amph more clean headroom. Surprisingly, it didn't. Where it was noticeable was on the high end of the gain scale. Completely diming the preamp gain ("9" is the highest on these Jet Citys, unlike the actual Soldanos that really do go up to 11) was about the same as it was on 6-7 with a 12AX7, which would make sense since the 5751 is supposed to have 30% less gain.