Rectifiers can definitely alter the sound, but as always, it's system and circuit dependent. I agree that the 12AT7s will have the most effect.
My 6SN7 preamp is also tube rectified, and a good NOS 5AR4 made a noticeable difference over the new production 5AR4s I tried.
David
My 6SN7 preamp is also tube rectified, and a good NOS 5AR4 made a noticeable difference over the new production 5AR4s I tried.
David