First, an ideal square wave does not exist in the real world, as it would have an infinitely fast transition time between its two voltage states. However, if those transition times (i.e., the risetime and falltime of the signal) are very small in comparison to the period of the square wave ("period" being the inverse of its "fundamental frequency," meaning the frequency of its lowest frequency component), then when a cycle (a single period) of that signal is graphically depicted (as on an oscilloscope) it will tend to pretty much *look* square.
Second, re:
To the extent that accurate reproduction of what is on the recording is the goal, as opposed to compensation for the poor qualities that are present in many recordings, accurate reproduction of "square waves" whose "fundamental" (lowest) frequency component lies within the audible spectrum is desirable, at least as a goal. Accomplishing that requires bandwidth to be considerably greater than 20 kHz, to avoid phase shift issues and assure adequately fast risetimes and falltimes (bandwidth, i.e., the range of frequency response, is inversely related to risetime and falltime). And also to avoid causing overall system bandwidth to be too low when the bandwidth limitations of the various components in the system are combined. It also requires that overshoot and ringing be minimal. Many phono cartridges, especially Low Output Moving Coils, are easily capable of accomplishing all of that, certainly as well as it can be accomplished by redbook CD. In fact an issue that not uncommonly arises with LOMCs is a resonant peak (i.e., an over-emphasis) in frequency response in the ultrasonic region or even the lower RF region. Redbook CD, on the other hand, is theoretically limited to a bandwidth of 22.05 kHz (1/2 of the sample rate).
In other words, reproduction of "square waves" in digital can often be more "rounded" than in analog!
To the extent that vinyl might be inherently warmer and less fatiguing than digital (and I personally don't agree that that is necessarily the case, assuming the recordings being compared are similarly well engineered), the reasons have pretty much already been cited: Absence of jitter effects; how harmonic distortion may be distributed among its various frequency components, as Swanny alluded to; absence of overshoot, ringing, and phase shift anomalies that may result in part from filtering that occurs in digital playback equipment and digital recording equipment (although cartridges and phono stages can also certainly ring and overshoot to some extent); and design deficiencies and compromises that exist in a lot of digital equipment, such as in some of the ways Steve cited. Also, both record surface noise and low level noise generated in phono stages are perhaps euphonic in many cases, adding a sense of ambience and perhaps masking undesirable artifacts, and their absence in digital may sometimes be a negative in subjective terms.
Finally, if what the person quoted in the OP said were true, all it would take to make digital sound like analog would be implementation of a "rounding" (i.e., bandwidth limiting) function in the analog circuitry that follows D/A conversion, having some desired bandwidth characteristic. Implementing that electronically is trivial. It seems safe to assume, however, that making digital consistently sound like analog is not quite that simple.
Regards,
-- Al
Second, re:
Turntables cannot reproduce square waves due to through time it takes for sound to get though the length of wire and the magnet that the wire is wrapped around in the cartridge.This is simply nonsense. So much so that I don't even know how to clarify it.
To the extent that accurate reproduction of what is on the recording is the goal, as opposed to compensation for the poor qualities that are present in many recordings, accurate reproduction of "square waves" whose "fundamental" (lowest) frequency component lies within the audible spectrum is desirable, at least as a goal. Accomplishing that requires bandwidth to be considerably greater than 20 kHz, to avoid phase shift issues and assure adequately fast risetimes and falltimes (bandwidth, i.e., the range of frequency response, is inversely related to risetime and falltime). And also to avoid causing overall system bandwidth to be too low when the bandwidth limitations of the various components in the system are combined. It also requires that overshoot and ringing be minimal. Many phono cartridges, especially Low Output Moving Coils, are easily capable of accomplishing all of that, certainly as well as it can be accomplished by redbook CD. In fact an issue that not uncommonly arises with LOMCs is a resonant peak (i.e., an over-emphasis) in frequency response in the ultrasonic region or even the lower RF region. Redbook CD, on the other hand, is theoretically limited to a bandwidth of 22.05 kHz (1/2 of the sample rate).
In other words, reproduction of "square waves" in digital can often be more "rounded" than in analog!
To the extent that vinyl might be inherently warmer and less fatiguing than digital (and I personally don't agree that that is necessarily the case, assuming the recordings being compared are similarly well engineered), the reasons have pretty much already been cited: Absence of jitter effects; how harmonic distortion may be distributed among its various frequency components, as Swanny alluded to; absence of overshoot, ringing, and phase shift anomalies that may result in part from filtering that occurs in digital playback equipment and digital recording equipment (although cartridges and phono stages can also certainly ring and overshoot to some extent); and design deficiencies and compromises that exist in a lot of digital equipment, such as in some of the ways Steve cited. Also, both record surface noise and low level noise generated in phono stages are perhaps euphonic in many cases, adding a sense of ambience and perhaps masking undesirable artifacts, and their absence in digital may sometimes be a negative in subjective terms.
Finally, if what the person quoted in the OP said were true, all it would take to make digital sound like analog would be implementation of a "rounding" (i.e., bandwidth limiting) function in the analog circuitry that follows D/A conversion, having some desired bandwidth characteristic. Implementing that electronically is trivial. It seems safe to assume, however, that making digital consistently sound like analog is not quite that simple.
Regards,
-- Al