advice for mono cartridge

If it's of any use to you, I bought a Shelter 501 Mono about a year ago.  Although I don't use it much out of sheer laziness, with the mono mode switch available to me, it's darn good, cheaper than some of the Miyajima's, and I have yet to hear a rationale for why "true mono" is going to be any better than a stereo cartridge bridged for mono, or a mono switch, for that matter.  One vinylista claimed that using BOTH a mono cartridge and a mono mode switch on his preamplifier sounded superior to either method alone; I have yet to verify that, because either method alone is SO much better than listening to mono LPs in stereo mode.

Correction to my post above: the Audio-Technical VM-510M body fitted with a VMN-40ML stylus (the micro-line contact stylus that comes with the VM-540ML and VM-740ML cartridges) is a mono solution with fabulous tracking. 

I use a Miyajima Zero on all of my mono albums new and old.  I do not play 78s. I have the Zero mounted on a Project 9.1 TT with the stock arm and heavy counterweight.  My crappy  McIntosh 6900 with autoformer has a mono button and to me sounds better with the mono switch engaged.
 I discovered a long time ago that mono sounds much better with a mono cartridge than with stereo cartridge and mono engaged on the preamp.

That’s valuable testimony. A dichotomy arises because if you switch cartridges then that brings into play the fact that you’re comparing two different cartridges. The mono cartridge might just be better than the stereo one. For each of us the outcome could be different. But you’ve stimulated me to do some serious comparing. One thing is for sure, mono LPs should be reproduced in mono if you want to get the most out of them.

After a year of playing The Beatles remastered mono LP set I bought in September 2014, I bought the Audio Technica AT-MONO3/LP HOMC (mono, of course). Amazon sells these cheaper than anywhere else--$118.53 with free shipping. It features a 0.6mil conical stylus. It is also "true mono" in that it only picks up the horizontal modulations. Dropping the needle on the record (a vertical contact) is dead quiet.

My tonearm accepts interchangeable headshells, so switching from stereo to mono is pretty quick.

It was a revelation. The remastered mono Beatles records were more focused, quieter, and dynamic. My enjoyment of these records jumped by 30%.

I soon discovered that I had some other mono remasters. One such is the Analogue Productions dual-45 rpm reissue of Nat King Cole's "After Midnight" abum from 1958. Another is "Drummer Man," a Verve mid-'50s pre-stereo hi-fi LP with Quincy Jones doing the arranging and conducting, and a reunion with Krupa's featured soloists, Anita O'Day and Roy Eldridge. 

I knew this record like the back of my hand, but with this AT mono cartridge, the playback "popped" as I'd never heard before.

Given the really high prices of some high end mono cartridges, the Audio Technica cartridge for $118.53 is a no-brainer, and moving coil to boot. I like the conical stylus as well. Much less hassle in alignment and setup, and the stylus pretty much tracks the same regardless of what part of the record surface it's tracking. The only thing that might be better would be a Shibata, but for $118 I'm not complaining.

Later, I retrieved some true vintage mono LPs recorded and pressed in the '50s and '60s, acquired from thrift shops for 99 cents each (one is even an original Everest recording/pressing of Mozart wind ensembles). Played on my stereo cartridge, they were too noisy; I originally played'em once and shelved them. With the AT-MONO3/LP I pulled them out again, and--Eureka!--the surface noise was gone! Just pure center-channel music. And some of these mono LPs (Roger Wagner Choral, Vince Guarldi's "A Boy Named Charlie Brown) were made in 1969! Who knew mono production was active that late--a full 11 years after the introduction of stereo LP.

It's a win-win all around--cleaner sound, better dynamics, focused center channel soundstage, and way less surface noise.