Try not to waste too much time though with tube rolling, nice for some experimentation but poor return on investment if obsessed.+10^10
Tubes vary unit to unit.
Tubes change over time.
There are 24 permutations of how the 4 tubes in the Freya can be arranged, each of which will have a slightly different response.
Spend the money on program and enjoy the music.
Reseat your tubes every thousand hours or so.
Live long and prosper.