I don't claim to be an expert Ron, Nipper gives me too much credit.

In basis, i subscribe to the Stu Hegeman school of thought that basically suggests that for an amplifier to be truly flat from 20 to 20k, the actual measured bandwidth will need to be much wider. This is evidenced in his designs for the Citation II and Citation V which both use very high quality output iron giving those amplifiers claimed response bandwidth of something like 5hz to 60khz. We'll save his use of what some feel is an excessive amount of feedback to accomplish this for a different discussion.

Suffice to say that of the many tube amplifiers i've owned and lived with, the Citations when fully and properly restored were my favorites.

So, i guess to answer your question, IMO, an amplifier with a rolled off response is one with a MEASURED frequency response bandwidth that varies more than -1 db within the 20-20k range.

I would also add FWIW, that just because an amplifier(tube or ss) has a rolled off response, doesn't necessarily mean it will sound bad. I had a home brew SET using TV sweep tubes that i was rather fond of running on my 9849's. Since i was driving speakers with limited LFE, and amplifier with limited LFE was of no consequence.

Ironically, you can probably look forward to a revised and improved version of that amplifier to become available to the public in limited quantities.

Now, i must return to the Krell powered Westlakes for an extended Saturday night session.