recently I bought a orange crush micro terror and I notice a dirty noise when I play my guitar on max volume, it’s impossible to play clean riffs, obviously the gain is low as possible. This not happen with the volume potentiometer at level 7, and even when I play low with volume on top. Is not the guitar already test it on another amp.
What speaker are you running into? Where's the tone control set?
The general idea is that a Gain stage is designed to be over-loadable for desired distortion, a Volume stage should be clean amplification. But note the demo video here, where he demonstrates a clean sound with both Gain and Volume at 12-o-clock. Guitar amps are often designed with the possibility of setting any control 'too far'. I suspect your amp isn't faulty, you just have to discover how to get the sound you want, and that it might not be available at maximum volume setting.