Thorens 125 MkII: MM or MC cartridge? What's diff?


I purchased a used Thorens 125 MkII. I'm pretty sure the cartridge is a Shure V15VMR. I'm pretty inexperienced with turntables, so I'd like to know whether the cartridge is MM or MC, since the Denon 3802 A/V reciever I'll probably buy will only accept MM. Since I'm so inexperienced, I don't know the difference between MM and MC, let alone what they stand for. Also, is the Thorens only compatable with one of these cartridges, regardless of whether it's a Shure?
Thanks,
Steve
sfd101
The Thorens will take others but this is just fine.
The Shure V15VMR is a moving magnet design -- one of the best, moderately priced MM's available (although superceded by the V15VxMR). Your cartridge has an output of 4-5 millivolts.

Here's a simplified explanation of the difference between moving magnet (MM) and moving coil (MC) cartridges.

In a cartridge, an electrical signal is generated by the magnet or coil moving in relation to one another. As the stylus/cantilever moves, it alters the flow of electrical energy created in the field between the magnet and the coil (in effect, creating an electrical analog, or representation, of the movement of the stylus/cantilever assembly). The electrical signal which is generated then passes to a phono preamp stage, which boosts the signal enough to drive the input stage of the main preamp.

The way in which an electrical signal is generated by movement of the stylus/cantilever assembly differs between the MM and MC design. With a MM design, the magnet structure is attached to the end of the cantilever, which is surrounded by the coil. As the magnet moves inside the coil assembly, it changes the electrical flux of the coil.

With a MC design, the coil (made up of wire windings) is wound around the end of the cantilever, which is surrounded by the magnet structure. As the coil at the end of the cantilever moves, it changes its position in relation to the surrounding magnet structure, thereby generating the electrical signal.

The theoretical advantage to the MC design is that the wire windings on the end of the cantilever have much less mass than a magnet structure, and the lower mass is easier to move. Hence, the MC design should be more sensitive and move more quickly, thereby improving transients, high frequency response, etc. (In a MM design, the coil can have many more windings, since it is in a fixed position that does not move. More windings = more gain.) The downside to the MC design is that it generates a weaker electrical signal than a MM design, thereby requiring more "boost" from the phono preamp stage.

Many of the theoretical advantages of the MC cartridge over the MM cartridge prove to be less than touted in actual use. All other things being equal, the MC should outperform the MM design, but the mechanism by which the cartridge generates a signal is not the only factor. Cartridge body resonance, tracking ability, the amount of boost required by the signal (weak signals require more preamplification), etc., all play a role in how well a cartridge performs.

In actuality, there are a number of very good MM (Shure, Grado, Rega, Picering, etc.) and MC (ClearAudio, Dynavector, Sumiko, Ortofon, etc.) designs, and your eventual choice depends in part on your personal listening tastes and the rest of your system.

Your Thorens turntable comes with its own arm, which is a decent arm, although not the best available. (It is held by many that the turntable and tonearm are actually more important factors in the overall result than the cartridge.) It will probably perform just fine with either MM or MC cartridges, provided the cartridge compliance/tonearm resonance point (the point at which the tonearm starts to vibrate and cause mis-tracking) is compatible. Without getting too technical, the issue here is one of tonearm mass vs. the cartridge compliance. What is necessary is for a tonearm to remain stable, without movement, thereby allowing the cantilever to move freely in relation to the grooves in the LP. If the tonearm also moves, the cartridge cannot track properly. All cartridge/tonearm combinations have a point at which resonance sets in, and this resonance point should be in the 10-12 Hz range. If the resonance point is above this point, it will be audible, and if lower than this point, there will be mistracking problems (potentially severe). Therefore, the mass of the tonearm must be compatible with the compliance of the cartridge.

Based on my recollection of the mass of the tonearm of the Thorens 125, the tonearm on your table should work fine with the majority of MM cartridges (including your Shure), and medium to higher compliance MC designs. The tonearm will probably NOT work well, however, with low-compliance moving coil cartridges.

Hope this helps. If you have more questions, please post a follow-up for me or others to answer.
Nice to see someone taking 15 minutes out of their day to explain cartridges like this. Sweet piece of work.