How Long Should One Wait Before Switching When A/B ing

The best way is to compare is to match timing and SPL and then A to B instantly as much as you want a quickly as needed.

Some of the newer DACs are very good for this as they lock in to a signal in a few milli-secs. Many DACs are slow at switching and synching - some will change the pitch of music for about a second while they adjust timing to a new source which can lead to perceived differences.

All you need is a couple of hours and you need to select a variety of music (at least 10 or 20 very different tracks) to test as differences may not be easily audible with all tracks.

My experience with the latest DACs is that they are becoming very close in sound. Lots of good choices.

For a true test the output voltage of each device must be adjusted to be the same! Otherwise all bets are off!

The problem with long term listening is that your brain will adjust to the audio signature of the sound. A bit like some people living near train lines being able to shut out the sound whilst others becoming increasingly intolerant etc.

The advantage with long term listening is that you get to know if you like the sound, if it grows on you. A bit like meeting someone you didn't like initially but becoming a good friend later. You can also learn about yourself in the process. 

For comparison purposes you can't beat direct immediate switching. Of course volume levels need to be matched closely etc. But the results can be night and day.

In a perfect  world all dealers would offer this facility.

I think short term comparisons can more confuse than help, in that it gets you focusing on the "audiophile" aspects of sound reproduction, whereas long term listening gets you discovering how much musical enjoyment the change in gear brings you - - and isn't that the end goal?  Do you get drawn into the music more, do you stay engaged and just want to keep putting on the next record (possibly at the detriment to your sleep schedule!)?  That's what long term listening reveals.

Short term highlights the highlights (wow, those smooth highs! that punchy bass!  that creamy midrange!).  These individual elements might contribute towards a better musical experience, and then again, they might actually detract from it, drawing your attention to hifi details as the expense of emotional engagement in music.  So, give it all time to soak in.  That is the process that absolutely works best for me.

To me the key issue is: listening to music you absolutely know and have heard many times.Hearing strange music just does not work for me at all. One plus I have always seen as a great thing when auditioning is the discover something I never noticed before n the music.                                   
So with a test, having the recording be utterly familiar would be my #1 priority.With the well know music, goes first impression. When I listen to a different setup, what is my first impression? And how does that compare with longer listening?So actually, and depending on the musical passage.. Some long, some short. More dependent on the Music than the theory.

Ah, one of the classic divergences of opinion. Good thing it's the only one in audio! ;) 

Is musical appreciation a cerebral pastime, or one primarily concerned with the senses?

For me the goal is to forget about sound quality and immerse myself in the music.

To do that, OK to get close, it's best for me not to think too much. Analysis almost always kills enjoyment for me, but others may differ. 

Whether it determining how something tastes, how beautiful someone is, or whether one system sounds better than another 9/10 my immediate impression is the right one. The other 1 time is usually so close it doesn't matter either way eg who was more attractive, Marilyn Monroe or Audrey Hepburn?

If only they'd starred in the same movie - then it wound have been obvious!

@zyac39 Having performed several auditions, mainly of cables/connectors, the one thing that makes A-B ing very difficult is the fact that the connectors on cables need to "seat" (or settle) before providing their best perofrmance-

The settle time is different form cable to cable, but can be as much as 24 hours.

I do not know if this is the same for components (assuming the components are both burned-in), but he fact that you have to connect them with cables would seem to imply this should at least be considered.

How did I approach this...
- first, find suitable audition tracks and listen intently for "cues" in the music that can be easily recognised.
- a cue might be a cymbal strike, or a particular bass phrase or the dynamics of percussion instruments.
- I document each "cue" with my existing cable/connector
- listen to the second cable/connector and note differences in each of the cues
- I then go back to the first cable/connector to see if you can identify any further differences.

Most of my auditions of new cables/connectors were conducted over many days and after long periods of listening to the "existing cable" in my system.

In the early days I just listened for easily identifiable metrics - like brightness, bass depth and control, image etc... but as the auditions progressed onto higher end cables I ffound myself listening to extremely finer details like the subtleties of the acsoustics of the venue (live recordings) like the reflections of sounds within the venue and the noises generated by the musicians - even the sounds sometime captured of noises outside the venue.

I have around 60 audition tracks containing all genres of music and I listen to them frequently just to keep the cues at the forefront of my memory

Hope that makes some sense - Steve