No that is not the solution, unfortunately.
I own both the Tube Box DS
and the DS+, that is very easy to open
That's the reason I was confused in my first reply above, which is obviously stupid if you inspect the Tube Box DS closer
On the Tube Box, you need to remove the tubes (not easy, had to get help from a friend and a pair of thin tweezers to get them out, wiggle, pull and patience)
Then loosen the screws and you can slide out the actual ampilifier.
Unfortunately, rolling the tubes to the pair said friend kindly brought with him (JJ Gold something don't know the exact type) didn't bring any improvement to my ears.
So back to original and case closed
ps: some sources mention the tubes are only used for impedance correction, i don't know if this is true, but would support my hearing abilities
ps2: very thin tweezers can grap the cooling element around the tubes