When have A/B comparisons led you astray?


I am curious how others have made A/B comparisons within their systems. What errors are encountered in this test? How do you avoid them?
I often think of my stereo system as a pair of ski goggles. Have you ever worn a pair of amber ski goggles all day and then been shocked at the colors presented to you when you take them off?
How does this phenomenon translate into the realm of sound?
mikewerner
Some years back I bought a $300-ish NAD cd player for my 2nd system. Just out of curiosity, I did an a/b against my twice-as-expensive Music Hall which was my "good" player at the time.

Based on that comparison, I thought the NAD did most things better, and after switching back and forth for a couple hours, I decided to keep the NAD in the better system, and put the Music Hall upstairs. A couple weeks later, I realized that I was never listening to entire cd's anymore. There was something missing with the NAD in place. It sounded good, I always got bored quickly.

Eventually, I switched back and found that I enjoyed the system more with the Music Hall, even though I couldn't identify anything it did better. So whatever magic that player had was apparently too subtle to pick up on when doing a/b comparisons. Lesson learned is that for me at least I've got to give a component enough time that I'm really just listening to the music.

By the way, I still have both players, and it's really a crap shoot as to which will work better in a particular setup. Turns out the NAD isn't inherently boring-it just was in that particular setup.
Last night I went to my son's Violin Master's Class.
Small venue - maybe 10 to 15 people present.
Piano and violin, that's it.
I have been listening to my digital source lately at home. I'm having trouble figuring it out. I know it doesn't sound real to me, but why?
What I am getting at is last night I feel like my ears woke up - again. The real sound is hard to describe but I feel that I am developing a sonic memory for it through training.
Ear training. My A/B comparison is moving toward Live vs. Recorded. Live is not a shifting reference. It is repeatable.
The Master's teacher was speaking about chords on the violin last night. A single note is in tune with itself. Only when compared or contrasted with another note can it be said to be out of tune.
To play a chord correctly on the violin, hold one note fixed and adjust the other to tune the interval.
So I agree. Does your system sound like live music?
Time will tell.
The recording process is the first step away from live, and the best equipment can keep that damage to a minimum down the chain, but once recorded it cannot be resurrected IMHO. Sure my system sounds like live music (unamplified acoustic), but I never confuse it for the real thing - A/B or Z.