Well, well thought I was the only one to experience this issue - good to hear the same symptoms. Little Mark II Bass amp does exactly the same thing - needs about 10 to 15 minutes before it produces any real output, as such I have been turning it on prior to actual performance. I have been very conscientious of a possible failure mid gig so I now carry a spare. Difficult to believe this can be due to a passive component in the pre-amp section - thought it would have to be a SMPS problem but I will be guided by better brain surgeons than me.
