When I listened to a bandwidth-limited, measureable delay, low-distortion amp with and without FB, the FB worsened the sound. The FB was obviously trying to correct a condition that had already passed and, therefore, adding a stale corrective factor into a later input signal.
Right, first up I guess I should say "Hello" to all. First post here and all that. Getting close to a lot of areas I am very interested in.
So, to weigh in:
I'm curious how you did this evaluation. Listening to a given amp in both open loop and closed loop is not going to be at all easy. What was the open loop gain? One assumes it must have been reasonably low, or you could not have done the test. So what was the feedback ratio? At what frequency is this?
Secondly, the idea that the amp was "trying to add a stale factor" really won't fly. I have no doubt that they sounded different, and your preference, but the rationale for the difference is very hard to believe. This goes to the root of how a feedback amplifier works. Yes there is a delay, and yes it is important. Indeed it is pretty much covered in the Nyquist stability criterion.
There could be a huge number of reasons why an amplifier could sound worse when the feedback loop was closed. If it had been designed to work open loop I would have grave misgivings that it would also operate correctly with the loop closed. It might operate OK, and indeed generally seem to be working, but immune to some of the well known failures of feedback design, that is harder to judge.