Replacing 12AX7 to 5751 for pre-amp

Be aware that you could raise distortion issues with certain circuits by this 12AX7 / 5751 substution. While electrically it may be benign, it is no assurance of optimum sonics. This info courtesy of circuit designer Ron Cornelius via Audio Classics concerning research on my Mac C-22. Good Luck

I'm not sure but, I believe that if you swap 12ax7's out and put in 5751's in a "phono" preamp that it will change the RIAA curve. If someone knows for sure I would like to know.

Thanks for your information. From my taste, 5751 is my choice than 12AX7. For AU7 or AT7, I want to try but I need more advice on my PAS 3. I do not want to get risky on my preamp. Anyone already tried AU7 or AT7 for 12AX7, let me know the sound

Like everyone else on this string;I too have been to "Joe's Tube Lore" on asylum. That said,
I replaced the line stage Telefunken 12ax7s in my Dynaco Pas preamp with Sylvania grey plates and it was a revelation.The sound was much more focused and nuanced.Lower sound floor and much greater mid to high definition.
There is quite of bit of Dynaco Pas info about using 5751s.
One of the things that some have said is that you don't want to use them in the phono stage,but I have to try it too! The amazing focus and definition alone make it worth trying. any body have more info on this?

great thread

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