Is there anything similar to this pedal allready ready to build?
Sounds like a compressor—implied treble cut, peak limiting, etc. Since it's one knob, fixed attack and release, knob is compression ratio I believe. Someone more knowledgeable about compressors may be able to reply with more info.
It certainly sounds like some kind of compressor.. I think it also cuts bit of mids.. My bandmate got him self a new amp, but his is missing shape knob of his behringer ultrabass head...