I would only add that - per Tom's mention of "data points" ... All tge subsequent processing does is time-shift those points. The fact that an improvement in sonic quality happens over and above the original non-timebase-corrected audio indicates that the audio was captured with sufficient data points to begin with, which calls the question of whether digital is granular enough to accurately sample the audio.
Please pardon the mispellings and occassional insane word substitution I'm on an iPhone
> On Nov 23, 2015, at 10:41 AM, John Chester <[log in to unmask]> wrote:
>> On 11/23/15 7:27 AM, Tom Fine wrote:
>> There is an argument to be made that analog media playback can't possibly offer that many data points to be collected. To wit ...
>> 1. when you play a tape, you are fighting the laws of physics. For one thing, no transport provides a perfect ride across the heads. Resolution is damaged by wow and flutter (time-smear), plus imperfect tape-to-head contact cause by anything from uneven head wear to imperfections in the tape surface to simple dust and other particles in the air. There's also static electricity and other results of friction. Then there's the fact that some tapes are slit perfectly enough to ride through the transport with relatively even track-tracking (i.e. relatively perfect azimuth throughout the tape). Tape electronics, especially old ones, are prone to what are now considered high levels of distortion and noise, and unless they have been thoroughly overhauled, aging components compound these problems.
> My objective, when transferring analog tape to digital, is to perfectly capture all of the imperfections of the tape recording, without adding any subjectively obvious errors caused by the digital recording process. To achieve this, errors in the digital recording process must be very much smaller than the errors in the analog recording. I assume that digital tools to correct analog imperfections will continue to improve, and I should therefore do a transfer which is good enough to allow use of these improved tools in the future.
> If I am only interested in capturing the audio content of a tape, I find that using a good converter running at 96/24 is the minimum requirement. Listening to transfers of a high quality tape recording, I do find that I can hear a difference between 96/24 and transfers done at lower sample rates or bit depths.
> When I'm doing a Plangent transfer, I also need to capture bias. If bias frequency is below 90 kHz, it can be captured directly at 192/24. For bias frequencies above that, we currently use special hardware to convert the bias to a lower frequency. To directly capture all of the information we can currently recover from analog tape we'd need to use 768/24, which is not yet available as off-the-shelf hardware.
> I don't find it very useful to ask what what level of digital imperfections would be comparable to the imperfections in a high quality analog tape recording.
> -- John Chester