Thanks guys for the feedback. Attached is a photo of what I did shortly after receiving the instrument about a year ago. You can see I raised each string by placing plastic shims on the nut - they're made from pieces of electrical wire insulation - cut along they have half-barrel profile that fits the shape of the string and gets into grooves on the nut better than flat shims. This did stop the buzz entirely, but this quick fix is not suppose to be a "proper" solution. The action now is about 0.35mm (the thickness of my business card, I think - typical one). The card fits easily under each string now, but does not fall off, so I'm assuming the action is the same as the card thickness, 0.35mm. The strings are Tomastic Spirocores, I think medium tension. These are NOT the ones that Mirko installs by default, but I've ordered the bass to be made with these in mind, he installed this set, so he knew how to accommodate and set up the nut for these particular strings. He is an expert making MK's so would know the difference in thickness, tension etc. of strings he had on hand before the instrument was even built. That includes "dressing" the board, I don't believe it was done incorrectly, although could probably be improved. Yes, playing now is a bit harder, especially near the nut - it takes more force to stop on F on E string that without shim, but that's expected. Plucking technique always matters, but I don't believe one can stop circular motion of a string if it's plucked side ways, parallel to the fingerboard rather than pulled away from it and released. In this case of course it will initially slam into the board, but that's one instant event, not sustained buzz when it repeatedly touches fingerboard as vibration dies out. I'm thinking of making the nut itself adjustable so a flat shim goes under it rather than have individual shims under each string. Then it can not only be raised/adjusted, but left and right side can be raised by different amount if needs be. Is this a bad idea? Glues in place nut is of course always better, but I'm thinking if I replace (keep replacing) strings to find optimal ones, every new kind will require new nut setup anyway. Filing deeper groves is one-way street, this can be done without replacing it, but if I need to raise strings of filed too deeply by mistake, a new nut is in order unless I can make it adjustable by swapping out, say, thin sheet metal shims under it. It would be simple enough to make it such that prevents the nut from moving up as strings being tightened when tuned. Like a couple of small pegs it will sit on. Is adjustable nut a bad idea in general? Such feature will be rarely used, but the same argument applies to the bridge, and nevertheless, these days they are being made adjustable. Oh, BTW, my other cheap EUB (Stagg) does not have this buzz - the same Spirocore strings and the same action under the nut (AND near the end of the fingerboard - 6, 7, 8 and 9mm under G, D, A and E respectively), the same playing technique...
