I used 5751s in my system to great satisfaction when I was using monitor speakers. I later moved to full size speakers and the system sounded flat. For the larger speakers I went back to the 12AX7 tube and it provided significantly more dynamic performance.
Jolida jd-502p
Anyone using 5751 tube to replace 12ax7's in a Jolida. I have read that it may not work well with some circuit designs. Also curious about what other Jolida users are using?