Dear Ctm: +++++ " It may still be possible to compare a MM and a MC cartridge, but only if one has a phonostage with identical mm and mc performance at any fixed overall [system] listening level. I am not an engineer, so those who have more technical know-how please chime in. Does such a phonostage exist? If so what tests does one perform to determine how similar or different a MM phonostage is from one designed for a MC without using a cartridge? " +++++
This subject is of paramount importance to really know exactly the quality performance of any MM/MC cartridge comparison.
The first " method " is to compare both phono stage specifications: RIAA accuracy, frequency range, signal to noise ratio, distortion level, crosstalk, slew rate, etc, etc.
Second to know the designer skillfull/know-how and targets on his design.
Third, when you hearing through both MM and MC stages.
+++++ " Does such a phonostage exist? " +++++
Absolutely, the Essential 3150 where both totally independent phono stages were designed to each one ( MM or MC ) phono stage needs, this means that both stages are not identical in its design and parts but have identical quality performance.
Regards and enjoy the music.
Raul.