? Tube Replacement Question ?

I would check with ARC but I believe it's every 5-6000 hrs. Distortion does go up as the tube ages and sometimes it happens so slowly you don't realize it until you replace them.

You might want to consider using tube dampers in the phono stage, at the very least. These tubes are more susceptible to micro-phonics due to the increased gain in the phono stage. When you are using the phono stage you are actually using the phono stage and the high level stage together to get the necessary gain. I use the dampers in both the high-level and the phono stages with excellent results. The ARC tube dampers work very well and are inexpensive.

Mapman the new rubber "O" ring dampers are removable and reusable, just don't cover the plate of the tube. Move the ring so it's above the plate structure. The older clear dampers used to melt into the tube.