But then the question of “Does vinyl sound better“ is an impossible question (a non-question) because for a given LP it’s impossible to known what digital delay lines were used in the old pre-compact disc days.
It seems the digital-delay-lines argument prevents any meaningful comparison between LP to LP (never-mind LP to CD).
The "digital delay line" aspect relates to ideas that conversion to/from the digital domain "corrupts," "contaminates" or limits the "resolution" of the signal in a bad way.
The fact is that
high quality digital conversion (which today, as this site has established, does not have to be "expensive") can be considered to be
transparent.*
The "corruption" (error) caused by transferring to and reading from vinyl, compared to digital, is orders of magnitude greater.
As a crude analogy, digital conversion adds microscopic particles, whilst vinyl is like pouring chilli sauce over the signal, then driving a truck over it for good measure.
(*OK, it can be debated whether it's above/below the "just noticeable difference" level. Vinyl artifacts, however, are
unquestionably audible.)
How to find out if vinyl "sounds better" than CD in a fully controlled way? One option would be to use a digital emulation of vinyl, one that does a good job of modelling its behaviour...
I suppose a live feed from an extremely high quality all-analogue signal path (i.e. not first recording to analogue tape or any other medium) could be cut it to vinyl in real time whilst simultaneously capturing to digital?!
Given everything above... Is this
really necessary?
(Better test is adding controlled distortion to signals, by which I mean fully mixed music and not single instruments, sine waves, or electric guitars, etc., to see if small amounts result in a perceived improvement in sound quality--and it can--and what amount causes a decrease.)