Simaudio 600i V2 volume control.

Yes, I think that it is a faulty optical encoder based on the sim system. It did work for a period last night but again today it does not. sometimes it will work other times increases volume in both directions. Very disappointed as the sound of the amp is wonderful. Time for a return. Thanks for the comments. 

Sorry to hear you need to return it .   Unfortunately that can happen when something is stored and not used for a long time.  Good luck with your search.  

That's not right.  I have the 600i v1 and am unaware of any setting that would make that possible.

I have found if I jiggle the volume/select knob just right and hurl the correct foul insults at the amp it returns to normal function. Just giggling and insulting by themselves does not work. Now it is working correctly but will talk to the seller about remedy, it is a very reliable audio dealer so I am sure that they will help me out.  It really sounds wonderful with a MSB analog dac and Dynaudio C1 platinum speakers. 

If you really like it and they will cover the repair and shipping it's probably worth the effort.  Moon is good stuff.