So completely trivial Plug & Play it ended up being not because the adapter initially to monitor not correctly recognized and offered as a native resolution only 1280x1024, although the monitor with 1680x1050 dissolves. Result was logically a scaled, distorted, blurred image. A research on the web and a few attempts to push 1680x1050 as adjustment, unfortunately, also brought not the expected benefits.
Already halfway abfindend with the return, I tried the panacea for computer problems: restarting the computer ... and lo and behold: Native resolution, excellent sharpness and no flickering - Perfect!
The error I explain this: Inasmuch as infected an actively-supplied with current digital-to-analog converter in it, and this should be "asked" with no connection to the monitor by the computer, which is its native resolution, "answers" it with 1280x1024 as a standard. And the converter "asks" until the next time back to the monitor.
A small à la Hinweiszettelchen Swedish furniture over such Troubleshooting would have been pleasant and had confusion avoided, unfortunately, can also be found on their website to no info. Therefore, a point deduction.