In relation to Salectric’s post, for most of my audio life, which is a long time, I played both stereo and mono LPs with stereo cartridges into a stereo circuit, and I never thought much about it, except I always preferred the results with stereo LPs in that set-up. Then, with the resurgence of interest in mono, and because I had acquired a preamp with a mono switch, I started listening to mono LPs played with a stereo cartridge into a phono stage set for "mono". The results were a revelation, and one can immediately understand the appeal of mono LPs. So, to me the main reason for buying a mono cartridge is because mono LPs sound best in mono, for a lot of reasons that I don’t want to detail. You can achieve mono reproduction either with a mono cartridge or a mono switch on your phono, or both. Among mono cartridges, there are only a few (like the Miyajima and the EMT monos) that were built from the ground up to be mono. Most are stereo cartridges where the two channels are internally bridged. Does this difference in construction make any difference in the quality of the mono output? I simply do not know; the makers of the true mono cartridges would like us to think so. In any case, I can make do with a mono switch only. I don't feel that I "need" a mono cartridge for my system that has a mono switch in the signal path. My problem is that i have two systems, and the phono stage for one of them does not have a mono switch; I want to buy a mono cartridge for that system, now that I have experienced the benefits of mono reproduction.
Here’s what happens in my system when I flip the mono switch before playing a mono LP with a stereo cartridge: The LP surface noise goes down significantly. The highs coalesce and sound more defined and extended. Instruments are easier to pick out in a band or orchestra. The bass acquires greater definition and actually seems to add another octave on the low end. There is actually a semblance of a stereo effect, too, because the brain picks up cues from the sound pressure and phase differences picked up by the microphone. What’s not to like?
