Hi Syntax, this info is copied from my reply to a similar question on VA. Hope it helps some. Good luck and report back.
Because I own several hundred mono LPs, I've done a bit of research and made a few purchases, but unfortunately have not put my own system together yet to offer first hand experiences. So all I can offer is a summary of my reading.
* Mono VS stereo cartridge - I think it will depend on how many mono records you own in deciding how much trouble you want to go to. Also, are they original pressings or reissues? Two considerations are styli size/shape and cartridge design.
Styli -- I believe you must first consider which records you will be playing before buying a mono cartridge. Note this applies only to 33.3 LPs, not 78s which have at least 3 mil requirements. Dates refer to master cutting, not date for performance. This is a function of the groove size/shape created by the cutter head.
Pre-stereo era monos (roughly '48-'57), select a 1.0 mil conical stylus.
Early stereo era monos (roughly '58-'68), select a 0.7 mil conical stylus.
Recent mono reissues (mid '90s to present), select a mono cartridge with a modern narrow stylus profile or a stereo cartridge if you have a mono switch. From my research, mono cutter heads are no longer available so mono reissues are now cut with stereo heads, thus modern narrow profiles are recommended for playback.
Lyra may have been the first to promote narrow profile stylus tips for better performance in mono cartridges. I think this may be true for playback of the modern mono reissues, but not as good for older originals. This is not to say a mono cartridge with a narrow profile stylus would not work on earlier pressings, it simply would not be optimal.
Design -- Another question where I have not seen agreement is the basic design of the cartridge and how the coils or magnets are wired. Most older mono cartridges pick up signals only from lateral movement. This is why they are claimed to be quieter in playback. Some current production mono cartridges are said to be stereo pickups that are simply strapped internally. Grados are mentioned in this regard for example. From what I know, this would be no different/better than a mono switch on your preamp or phono stage and a stereo cartridge.
* EQ for older recordings. The RIAA curve was approved by 1955 but not adopted by all record companies until the early '60s (a few in Asia did not comply until the '90s). So again, what you need will depend on what you have to play. All reissues for the past 15 years should have RIAA.
Because of the number of mono LPs I own, I've purchased a mono cartridge (Denon 102) and a second tonearm to allow for dedicated playback once I finish building a custom plinth. I have not decided yet about additional EQ options (which can cost from $300 to $10K if you don't already own a vintage preamp). I'm trusting all this effort will prove to be worthwhile.
