First let me point out that DBT in its various forms is a well proven
statistical evaluation technique for testing a wide range of diverse items.
For the vast majority it works extremely well however it is already
recognised that where the outcome of the test is not a clear yes/no answer
e.g. testing pharmaceuticals it is necessary to have both a large sample set
and three groups to measure against the so called placebo effect.
I believe that DBT is unsuitable for Hi-Fi evaluation as the detection
method (you the listener) are anticipating a change to occur at some point
and will be listening to changes not trying to enjoy music. Couple this to
the fact that what you hear is just an interpretation of the vibrations
received at the ear and the fact that sound will change as the listener/s
moves etc. It is no wonder that DBT has only given positive results for
major changes in sound.
Can anyone point to a Hi-Fi DBT test where no changes were actually made in
the source material to check that the audience could perceive no change ? I
think that the false positives raised by such a test would invalidate this
testing regime ? Seeing as though a proportion of contributors to this group
insist on such validation to prove differences it is very important that
they should first prove that their testing procedure is without flaws ?

With the poor conformation device of a person to identify changes in sound
the sort time interval switching proposed by some advocates must surely be
impossible to identify in a piece of music ? Music is far too complex to
expect anyone to correctly identify all but the most severe changes to be
correctly identified unless a long time period is set between changes ?
Should the test actually be made using white noise ? Using a long period
between changes is also flawed as audio "memory" of how a track sounded is
also unreliable.

Is there a solution ? For short term testing no. Some changes can be
detected electronically if the material remains in the digital domain but
once the sound has left the speakers there are too many variables. For our
Hi-Fi club we still use what for us is a less flawed method of a-b
comparison (preferably blind) on repetition of a range of tracks followed by
a longer term evaluation over the next few weeks.
I look forward to any proof that DBT for Hi-Fi has been validated.
Regards Richard Wall
New Ash Green Hi-Fi Club