Interesting question. Fantastic amp. I've had my Tone Master head for about 13 years now. One of my favorite amps. I had it in for service one time and the tech stated that part of why it sounded so good was the lack of the negative feedback loop. Interesting, huh? I'm technical enough with amps to be dangerous but, don't know enough about negative feedback loops to know if that's an accurate statement or not.
Thanks for the reply. I am sure that the effects of a NFB loop will be subjective (like everything else), but my research has indicated that its possible to install a switch or pot that would allow an easy transition back and forth. However, I dont know if that is a routine mod or only applies to certain amp circuits? I am going to consult my local tech. He specializes in Fender amps, and usually has a fast turnaround on this type of work.
Hopefully we can get a few others to weigh in on this topic.