Burning in anything in the phono stage is tough. I bought this inverse RIAA circuit http://www.hagtech.com/iriaa.html from Hagerman Technology which really speeded up the process. It's really hard to know what's going on 'til you've gotten everything burned in and it's easy to put on a couple of hundred hours in just over a week with the Hagerman.
You do need to be certain that your arm damping fluid is at the correct level. Either too little or too much can impact bass response.
Dave
You do need to be certain that your arm damping fluid is at the correct level. Either too little or too much can impact bass response.
Dave