Hi Bluesking
I tried your 180Kohm resistor mod to the tonestack input and I also replaced the  bias bypass cap from 5uF to 2.2uF, as you described in you pm to me. It’s really a very big difference. Now my amp sounds as I want it to sound. I can get the John Mayer sound and also other smooth lead sounds, which I couldn’t get before. Your mods definitely worked out for me. Thanks a lot for your help and advising.
 

Hi Bluesking
I had my OTS 50 build Nik. From the first time I played the amp, it didn`t sound the way I expected it to sound. It was to flubby (as you discribed) all the time, with, or without PAB. I mailed Nik for help and he immediately replied everytime :-). Finally I ended up taking all the bass down to allmost zero. But still the sound is not nice. Flubby at normal volume on the lower strings (`74 Stratocaster with `69 fender costum shop pick-ups) Do you think I could have the problem as you had? Might your mod be the solution?
Thanks for your answer.