The tonestack of this amp is heavily inspired by the 2555 tone stack (which came out like 2 years before this mod was done.
Now the 2550 tonestack works with a logarithmic 100k mid pot and a linear 220k treble pot, apparently reinhold made a mistake there and used a linear pot for the mids and a log pot for the highs, which makes sense for all the common tone stacks which use linear mid pots, but the 2550 TS works differently)....So I put a linear pot in for the trenble and a log one for the mids and it fixed ALL the issues I had with this amp.
Now it sounds great with everything around noon, everything is muvh more controlled and the amp just got so much more versatile...I'm happy