Turntable choice for mono records

@mijostyn You're missing out, but being a grown-up, you do you! I have no perception of stereo, having only one ear. But I still perceive a benefit from a mono cartridge playing a mono recording: much less surface noise. Since my mono records are all a bit old now, that is welcome.

Elliot, I respect the fact that you have put a lot of effort into mono playback of mono LPs, but I have to question the following statement, with reference to some shortcomings you listed above of using only a mono mode switch to listen to mono LPs:

"It DOES NOT reduce any surface noise, warps, debris, any vertical movements picked up by a stereo cartridge, it in fact doubles that, as any L or R are combined, then doubled."

I was taught by reading that the L and R channel noise(s) generated by dirt or damage in the groove walls are (predominantly) out of phase with each other and will thus be cancelled when the two channels are combined, as when one uses the mono mode for playback.  This concept is consistent with my repeated experience that HF background noise is reduced when I listen in mono mode (without also using a mono cartridge).  Also, I don't quite get what you mean by "doubled".  If the noise is cancelled because out of phase, then nothing is left to double.

The whole discussion is complicated by what definitions we use for "mono LP" and "mono cartridge".  So we could be talking past each other.  As you know, most mono cartridges for sale today are actually stereo cartridges in which the two channels have been bridged internally, in order to generate a mono signal.  That is really no different, except in one way, from using a mono mode switch on a phono stage or linestage.  The one difference is that in the former case, the mono signal is generated BEFORE RIAA correction and amplification takes place in the phono stage. Whereas in the latter case, the combining of the signals happens after those two processes have occurred. (Using a Y-adapter between the cartridge and phono inputs is really a bad idea in my opinion, because in that case each side of the cartridge is seeing the impedance of the other side in parallel with the input impedance of the phono stage.)  So I can believe that a mono cartridge, especially a true mono cartridge (one that is built so as not to respond to vertical motion of the cantilever) might have advantages vs using a mono mode switch.

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.