Phono playback is perhaps the hardest discipline in all things audio. Approaching it from the digital side of things will certainly bump into digital's limitations - and that would be , first and foremost, the frequency response. Phono playback has been shown to exceed FR of > 200 kHz - 40 years ago. Here is the only part of the most comprehensive and meaningful phono cartridge review ever published that is available on the internet - that of International Audio Review , Issue #5, May 1980.
This review deals with more real world issues of phono playback than any other to date. It covered pretty much almost everything that was available at the time - and cartridges that are direct succesors to the 1980 models are pretty much still available - in their evolutionary form(s).
Too bad that IAR aka Peter Moncrieff has placed copyrights etc as he does, preventing from making this document available to public for free. It answers LOTS of questions and dillemas of phono playback world, both from cartridge/stylus point of view as well as from the effects of electrical loading of carts by the preamp and associated cables.
I certainly do agree the SINAD test of phono preamps as of present does not reflect the performance in real life. Although I do agree that, for instance, PS Audio Stellar phono stage is on the expensive side, the unit can not be flawed in real world use. It performs well with most cartridges tried, both MC and MM types - it is quiet and allows music from the LP to get a notch higher. I do not own it, but have heard one in a friend's system recently ; to all those who pooed on it due to SINAD measurements without even seeing it ( let alone heaing ) live, I recommend to do some real world use of gear BEFORE repeating such excercises again.
To @ amirm : phono measurements are tough AND extremely expensive. That is due to test records, which for the most part are simply no longer available, are VERY vulnerable and can be destroyed with a single play. After such hiccup, the record needs to be discarded and replaced by a new, fresh copy. In 2021, that means $ - and lot$ of $$$$. The test records that have stood the test of time and became the de facto standard are almost exclusively vintage, long out of print rarities - and those $$$$ were there for a reason. It is in 4 digit price range NOS sealed copies go for these days. Unless you are an emerging manufacturer of phono cartridges that wants/needs to have these records cost no object ( no way to claim such and such specs for the carts without the test record that can furnish the proof of such claims ... ), you can forget getting any of these records at anything approaching reasonable price.
If you do plan to make any more serious phono measurements, please do observe the suggestions on the KORF blog
https://korfaudio.com/blog - particularly regarding the Issue #1 of phono playback, that is to say azimuth.
Although ANY stylus - no matter how expensive and how touted to be "perfect" - should be examined under the microscopre before ever allowing it to play precious/de facto irreplaceable (test) records, there still are defects and caveats in cartridge/stylus department that korf way of doing azimuth will weed out.
You would be surprised how large % of cartridges actualy available for sale can not meet the korf criteria. And should NEVER be allowed past the manufacturing plant door.
Any phono preamp issue(s) are minuscule compared to the azimuth problems of real world cartridges. Please note that almost no "vintage" cartridge review ( before about 2000 ) ever mentions the cartridge has been aligned for azimuth; most reviewers used for their reviews a tonearm with non adjustable azimuth, known to be correct ( mainly SME, later Linn , etc ) - and mounted and measured the cartridge just as any normal user would. The vast majority of comments like " sufficient , but assymetrical crosstalk (curve) ", " distortion in treble in one channel significantly higher than in the other " , etc, hint at the fact that the cartridge under test was OFF in azimuth.
The highest azimuth error in an otherwise impeccable cart/stylus I came across has been 3 and 1/2 degree; most are well within 1 degree, but to achieve symmetrical channel separation equal to or better than 35 dB the azimuth error MUST BE within less than 1/3rd of a degree.
Most arms/headshells that do allow for azimth adjustment do not have precise and repeatable way of dealing with so low error(s) - it is trial and error untill you get it exactly right.