12BZ7/12AX7 vs. 5751

Not getting the "whole tube rolling deal" is like "not getting the whole appreciating differences between things deal." Also, I'm a believer in 7025s as a 12AX7 swap, although results may vary. Is an accurate and full range tube tone a "SS" sound? This term is bandied about by term bandiers suffering from adjective deprivation. I prefer my music to sound tonally correct using my extremely refined ear, impeccable taste, serious demeanor, and finger burning tubes glowing for my amusement and aesthetic needs. Both ears actually, especially when they're clean-ish.

I can't comment on whether 12bz7 is a substitute for 12ax7/5751 however if it is my advice would be take advice only from those who have experience of your amp or go out and listen for yourself.

For me Sylvania 5751 are excellent, better than any 12ax7 I've tried but in another implementation they may not work at all.

Can be good fun exploring different tubes though expensive and a good measure of frustrating

Hi Grimace

I have been swapping 12AX7 tubes with 5751 type tubes in a Jolida Glass FX tube DAC. The RCA Grey Plate 12AX7 tubes from the 70s I had in the DAC made the music very forward and cymbals and highs really had some sizzle to them. Music was borderline unnatural sounding. I rolled in some JAN GE 5751 type tubes from the late 80s and it made the music less in your face and calmed down the highs by wide margin.

I'm going to try to find Sylvania 5751s at a good price but they seem to be getting scarce. There are a lot of GE 5751 tubes out there for you to choose from. Lastly some tube sellers have low gain options for 12AX7 tubes BUT from what I've seen these are for newer issued tubes. E.g. Sovtek, JJ, Tung Sol. I don't know if that could be another solution for you.

Good luck.