Turntable choice for mono records

This discussion has been very educational. I greatly appreciate the friendly debate over the value of mono. I have also heard from audiophile friends that a mono setup brings out a deeper soundstage and sometimes better imaging which seems to run counter to the argument that the improvement is only related to surface noise reduction. Have any of those using mono cartridges experienced these improvements compared with the same LP played in stereo (with/without) a mono switch?

Since the point was raised, which if any of the cartridges I am considering would be "true mono" and not bridged: AT33, Ortofon 2M, and Shelter 501 II? If all are bridged, what are the true mono cartridges?

vac..., You wrote, "I have also heard from audiophile friends that a mono setup brings out a deeper soundstage and sometimes better imaging which seems to run counter to the argument that the improvement is only related to surface noise reduction."

The language is a little confusing, because it could be taken as a claim that mono is superior to stereo in conveying soundstage and imaging, which is of course false on the surface. So, I think (or hope) what you meant to ask is whether using mono mode, via a mono cartridge on mono LPs is superior to using a mono mode switch, when playing mono LPs. That is the $64 question that I cannot answer, because I have not used a mono cartridge. This is where Elliot claims that a mono cartridge is superior to just the switch. Please see above where I described the mechanistic difference in terms of signal processing, between using a mono cartridge and using mono mode. (Of course, there is nothing safer than wearing suspenders AND a belt, so possibly using both mono mode and mono cartridge is best of all.) I can only say that I do hear suggestions of soundstage and imaging with just a mono mode switch that are not readily apparent when using stereo mode, with mono LPs. But Elliot may be correct that it gets even better with a mono cartridge. Sorry, but this boils down to listeners, systems, and subjective judgement.

As to which of those particular cartridges are true mono types, that is also a bit mysterious because manufacturers seem to try to obscure the methods they use to make mono cartridges from their stereo cartridges. (All 3 examples you cite are models that are also available in stereo.) I have a hunch that the Shelter mono is a bridged stereo cartridge. Ortofon is a bit tricky, because their literature is ambiguous, and they definitely try to leave the reader thinking their mono cartridges are true mono. Some may be true mono; I am pretty sure that some others are not. I never investigated the 2M. And finally, the AT33; I dunno. There are only a few brands where you can be sure of true mono. One of course is Miyajima. I think one of the Denons. Maybe others can help.

@lewm sorry that I wasn't being clear. I was referring to the situation of a mono recording (especially one cut pre-1968) that is played with a mono cartridge vs. the same mono recording played with a stereo cartridge with or without a mono switch  on the phono stage or preamp engaged. My reading and conversations with others suggests there may be a noticeable improvement in sound quality for the "pure" mono system over the stereo setup if they are of comparable quality. 

I very much appreciate the insight that manufacturers, like Ortofon, which make the same level cartridge in stereo and mono, might be more prone to bridging, than a company that specifically manufactures a mono cartridge within the same class. The "bridged" vs "true" mono cartridge seems like it could be an important caveat to my statement above.

I think I did respond to the question you re-phrase above. You are collecting a bunch of opinions from strangers, but there is no reason to believe that a bridged mono cartridge is any different from using a mono mode switch with a stereo cartridge, except the one I mentioned earlier: With a bridged mono cartridge, the derived mono signal is then amplfied and RIAA corrected, With a mono switch, the mono signal is derived after amplification and RIAA correction have taken place (but keep in mind that the LP is feeding a mono signal to both channels, regardless).  The only way to tell whether that difference is important to you is to try it both ways, IMO. I would not necessarily go by the opinions of others.  AND you should keep in mind that any mono cartridge may sound different from any stereo cartridge, just because they are two different cartridges. That's always a confounding factor. For that reason, I would be loathe to generalize.