Unitygain mode with continuously beeeeep.

If you disconnect the AV kit from the NAC202/NAP200 (i.e. unplug it - make sure amps are off when you do this) is there still the beep noise?

disconnected the AV-Receiver and the beep was gone. Okey then what could be the problem? time to change to a new receiver perhaps or is it a cable or perhaps an electric issue?

It can be a common problem with receivers that float the earth, exacerbated by connection to Av kit also floats and that is connected to cable feeds, sat feeds etc..  You should try an AV link ground loop isolator between the AV amp and the Naim kit (very inexpensive).  Lots of info in past threads on here.

You need to experiment here. The problem may, or may not be solved depending upon the source of the ground loop. But for the cost of an isolator...

I tried a supra ags-10k that should have stopped ground loop hum. Didnt work Sounded like s*it actually and even more hum than before. Then maybe its not the problem. I tried nac202 in bypass mode instead of unity-gain. Then it worked when i had volume at ten to twelve. When i had it at twelve as you supose to if you look in the "manual" the peep was there again. And i dont want the 202 in bypass beacuse it change volume both at the marantz receiver and 202 at the same time with the marantz remote. same frequens in both remotes. Real tired of all problems right now...

Yup, it's a real pain.  I just wish AV gear was properly earthed rather than left to float - something that only really comes at the higher end.  It makes mixing with earthed gear really hit an miss regarding humming and buzzing.

Not all isolators work well - have a search on here for some that have come recommended or speak to your dealer for any recommendations they may have.  Failing that, you could try flying earth leads?  Any thin cable should do. It can be a bit hit or miss as to where to connect on the offending item - RCA outer or chassis? Have read up on old threads on here.