Some general information about "modern" Mono Cartridges I used or listened to.
In a way I prefer those from Lyra based on their Design principles ( but a Shelter 501 mono sounds also very good). Lyra mono cartridges use a vertical coil which is only capable of detecting horizontal stylus movements (corresponding to mono groove modulation), and they have TWO identical mono coils to avoid the possibility of ground loops with stereo phono stages or preamps. For me, it is a step ahead ( I had with a cheap Dorian Mono better results than with much more expensive 'mono' carts from other Importers...) . Other cartridge manufacturers may use different methods, like using stereo coils and summing the outputs to derive a mono signal, but in my experience this way is no better than using the "Mono" button on a preamp, and will be limited by how well the two stereo channels match (crosstalk, phase, frequency response, output balance etc.). Generally, my experience here was not positive. Too mediocre. But cheap. For some this is a priority.
Another discussion is the time era from these Records, of course there are differences, but to keep the story simple, I use late 50's ++. I don't think that the differences between the original LPs and modern reissues means that much
for cartridge or stylus design. The commonly voiced concern with "wider mono grooves" has no meaning, in my experience. The most important thing is that the LP groove continues to have a 90-degree cross-section. Older LPs have shallower (and dirtier) groove bottoms, so a stylus that reaches particularly deeply into the groove may cause problems. In my experience, a line-contact stylus with a smaller major radius like 30um may cause problems with older LPs (and this is same for both stereo and mono records), and so for older LPs I would recommend a cartridge that has a somewhat larger major radius 70um, but it is not a general rule. Depends how fanatic you are, in what condition your records are and of course, what kind of Quality your Playback System has. The Lyra Mono have interestingly a different kind of Sound than their Stereo "brothers", more "juicy" with a greater sense of immediacy and presence. Has to do with the two coils, even when the output is only 50% from them...
Summary: Based on the superior tonal colors in the old mono records, much a much better low register the Mono Trip can be really interesting for the discriminated Listener.
