so,

problem has been solved.

it was really screw and female screw inside of the unit. and strange thing was that it was inside of two of three units what they had in shop….

the effect works little bit different then i originally supposed but after few hours spent with it, i love it more and more. it is just addictive!!! ,-)

i put few examples on this temporary link:
http://www.e-mental.com/temp/tube.zip

it is examples of the usage with microkorg synth.

tomas