I have one of these with the 8 inch cabinet. Great practice amp. The only negative is that the headphone sound is so bad as to be worthless. A shame as it is a great amp otherwise.
I don't own any headphones so I have not tried the jack.. I wonder if changing the tube out would affect that ?
I read on the Orange forums, that I-rig orange edition through your iPad or iPhone sorts out the issue you mentioned.