I've had some strange issues with my AFD100. I play a Gibson Les Paul Historic G0 (Guitar Center model) loaded with Sheptone tribute pups through the AFD100 and a bone stock 1960A cab with G12T-75 speakers, and the sound is great! If you have the presence on 8-10 that is. Everybody keeps talking about how bright the amp is on the AFD mode, and scrambling to the treble & presence controls when they first played through it. No such thing with my amp though, if I lower the presence to under 8 or 9, it sounds incredibly muddy, it's as if the presence control has no use below that setting (I don't hear a difference in the sound when the presence is set at '0' or '5') at all.
Can it be a faulty potentiometer perhaps?
Cheers