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Replacing 12AX7 to 5751 for pre-amp

Does anyone try NOS Sylvania 5751 replacing 12AX7 for preamp? My friend convinced me trying 5751. I did try them for Dynaco PAS 3 and woo sound is warmer, treble is softer special with vocal. Bass is more tighten than before. I want to try more AU7 or AT7. Do they ok to try? I know that we can replace any 12AX7 with other lower current.
sanjose_audio_guy
racamuti's avatar
racamuti
362 posts
 
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.
sanjose_audio_guy OP
28 posts
 
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
emorrisiv
313 posts
 
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

e
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