In general burn in will take the edges off. However the sound after about 10 to 20 hours is going to represent the end product to a great extent.
Your pre may not have a circuit they will work in as mentioned above. A CD player I bought early in the hobby just made a GAWD awful shriek of painful protest when I subbed them.
I recognize that many will argue that a tube fleshes out with time and it's true, but that takes place gradually over a long period. In the interim, however, the tube will show what it is going to be.
To me immediate burn in has almost always been a smothing up with some getting significantly fuller tones. However Flat earth to halographic soundstage is not what I have experienced.
It really sounds like a really bad pair of 5751s.
When they do work out, they function beautifully as a stage expanders with halographic imagery. I started with Jans and they sent me sliding down the slippery collecting slope.
Your pre may not have a circuit they will work in as mentioned above. A CD player I bought early in the hobby just made a GAWD awful shriek of painful protest when I subbed them.
I recognize that many will argue that a tube fleshes out with time and it's true, but that takes place gradually over a long period. In the interim, however, the tube will show what it is going to be.
To me immediate burn in has almost always been a smothing up with some getting significantly fuller tones. However Flat earth to halographic soundstage is not what I have experienced.
It really sounds like a really bad pair of 5751s.
When they do work out, they function beautifully as a stage expanders with halographic imagery. I started with Jans and they sent me sliding down the slippery collecting slope.