So. I love my tubes. But to get the best tube sound I find the amp should be set at =/+50% amplification, and the sound is even left biased at the lowest volumes (although I found the latter part in the solid state amp as well). So how do we get that cherry sound of tubes at various volumes with...

On the topic of standard pink/white noise, sine wave burn in tracks..   A) Would it not be key to the "burn-in" of headphones that they are exposed to pulses mimicking what they experience with real music? Particularly pulses mimicking typical bass beats or even rapid/abrupt changes in pitch...