Hi. Does anybody know the main difference between an MM and an MC cartridge? Why would you choose to have one or the other? Also, I am in the process of buying a system. Do you get better sound quality for your LPs by having a preamp with a dedicated phono input or by using an external phono amp hooked up to an AUX input? Thanks, MAx
The second question is answered by saying it depends on the quality of the phono pre amp in either situation. Your first question has been answered here several times. Cruise through the archives; you might learn something you weren't expecting to find along the way.
A MM cartridge works quite differently to a MC cartridge. The MM principle is to stick a magnet on the end of a pole called the cantilever. The cantilever is held at its middle point and on the other end is the stylus which is the bit that traces the groove. Now the magnet sits in the middle of the relatively large coils. When the stylus moves it causes the magnet to move and this generates a current in the coils. This current makes its way to the cartridge terminals.
Moving coil works very differently. Take the picture in your mind of the cantilever. Snip it in half and fix it at the point where the MM cantilever was simply a fulcrum. Now just in front of the fixed point, affix four relatively small coils. These sit in between the poles of the magnet. Now when the stylus traces a groove, it moves the coils within the magnetic field, generating the current that goes to the terminals of the cartridge.
There are advantages and disadvantages to both schemes. Since the coils are much smaller than those in the MM cartridge, the MC cartridge generates a much smaller signal. Typical values are 2mV for MM and 0.4mV for MC cartridges. This means that the phono stage for a MC cartridge has to have significantly more gain to bring it up to the 1.5V - 2V input that an amp expects. Doing this means the phono stage is more prone to background noise. Another weakness of MC cartridges is that since the cantilever is fixed to the coils, you can't replace the stylus without rebuilding the cartridge! Some manufacturers give 'body credit' when it comes time to replace the stylus tip and there are one or two 3rd party companies which make a living from retipping more expensive MC cartridges.
OTOH, MC cartridges have some benefits over MM cartridges. The cantilever in a MM cartridge is balanced around its centre point, and the magnet has very significant mass in comparison to the stylus. This means that when the stylus moves one way, the momentum of the magnet is significant when the stylus tries to change direction to follow the grove. This means that the stylus is always fighting in contention against the magnet and finds it more difficult to track the groove. MC cartridges don't have this problem. The coils have much lower mass than the magnet in a MM cartridge and they move a substantially smaller amount of distance so the momentum is much much lower. This means that the stylus finds it much easier to track a record in an MC cartridge than in an MM cartridge. In the process it allows the stylus to retrieve more detailed information than allowed by the MM configuration. This is one reason why MM styli tend to need fairly frequent replacement (1 - 3 years depending on usage) whereas MC cartridges only need looking at infrequently (3 - 5 years).
There are two other cartridge types which we have not touched on here. Moving Iron is a similar principle to MM, but suffers from less of the mass-induced tracking issues. This principle is used in few cartridges, the most notable of which is Grado, and fine cartridges they are. The other type is the High Output Moving Coil (HOMC). This uses the same method of fixing the coils next to the end of the cantilever. However, they use much larger coils in order to produce an output almost as high as that of a MM cartridge. Since the coils are larger they have more mass, but this is still less than that of the magnet in a MM cartridge, and since the coils move much less distance, their momentum is substantially lower. So you get many of the qualities of a MC cartridge without needing the higher gain of a decent quality MC phono stage. That said, if you had an MC version and a HOMC going through the same phono stage setup for the different gains, the MC will still show the HOMC a clean pair of heels in terms of resolution, clarity and depth.
In the end, which combination of phono stage/amp/cartridge you choose depends a great deal on what your local dealer has to offer you. Each combination sounds different. Typically, MM cartridges rule the roost at the less expensive end of the market. MC cartridges take over further up the chain so you will find few MM cartridges in the $500 and above price bracket, but loads of MC cartridges in that price range. You will find HOMC cartridges up to around $1000. For my money MC cartridges are wonderful, but only when you've spent the money on them. If your finances are restricted, then it makes sense to look at MM since entry level MC cartridges can be a little on the brittle side typically. This dovetails with the fact that if finances are tight, the phono stage being used will not be a particularly high quality one so it's wiser to go for the less noisy option which is MM. That said, if you have aspirations for the higher end in the fullness of time, many phono stages have both MM and MC capability. They'll usually be better at one than the other but at least they give you the option while you slowly upgrade your system over time.
You'll note I always talk about phono stages. This is because many amplifiers do not have phono as an option and so it's a more flexible solution to have an external phono stage which will open up any amplifier you like for future use. Then again, this means another box and another interconnect and therefore further outlay or further spreading of finances, so you need to look at your options carefully before taking the plunge.
Thanks Frank for the excellent explanation. My next questions is, can you buy a turntable and then choose whether to use an MM or an MC cartridge, or are turntables meant to have only one type of cartridge? From my questions, I guess you can tell I just started developing an interest in the field, but since I was little I had a cousin of mine who owned a Thorens (coupled with AR speakers) and I remember listening to a Mozart violin concerto and that was my best listening experience ever. My dream is to eventually own a Thorens. What cartridge do they take? Are you familiar with Thorens?
I am not that familiar with Thorens since their representation has been patchy at best in the UK for the last 10 years. However, I do know they make turntables from the entry level all the way to expensive.
In the whole turntable/arm/cartridge/phono stage thing, the turntable is the most important. A finely engineered turntable will allow both the arm and cartridge to work correctly. A badly engineered one will not. You need very small problems in the turntable to make life very difficult in the arm and cartridge. The most important part of the typical turntable is the bearing on which the platter rotates, followed by the motor.
Most quality turntables are belt-driven. The belt allows an element of decoupling between the motor and the platter. Motors should be silent and in most applications their vibration is so minimal as to be negligible. In a turntable, a motor's vibration can cause enough of a problem to actually make the stylus jump out of the groove! A belt allows variations and vibrations to be dissipated (to an extent) before hitting the platter. A high quality power supply can cause a motor to vibrate less too, further lowering the noise floor of the turntable. Most high end decks have intelligent power supplies which monitor and adjust the current draw to minimise the energy in the motor and therefore minimise its vibration.
The arm is the next most important thing. It is the job of the cartridge to drive the arm, dragging it across the record. Any play in the arm's bearing introduces friction and extra work for the cartridge. The relationship between a stylus and the arm is such that if the groove were a furrow in a field and the stylus is a hand hoe, then the arm would be a gantry two storeys high and quarter of a mile long to its pivot. Now imagine trying to trace the groove with that attached to your back...
Given the above explanation, you'll see that the most important thing is the deck. Obviously, you need a cartridge so spare some cash for that, but do a bit of research on turntables before you dive in. Thorens is a good brand. Here are some others which are worth considering:
"In a turntable, a motor's vibration can cause enough of a problem to actually make the stylus jump out of the groove!"
Holy resonant frequency, Batman!
"It is the job of the cartridge to drive the arm, dragging it across the record."
It matters little to this conversation, Frank, but wouldn't you agree it is the task of the record groove to move the tonearm from one end of the groove to the other? It is the job of the tonearm to hold the cartridge's cantilever/stylus securely in the groove as it traverses the path. Ask anyone with a linear tracking arm.
Thorens does not manufacture cartridges. They have reinvented their table line and are competitive with other brands. In the lower price ranges of turntables you will not have the choice of what tonearm can be used with any particular table. The mass and the compliance of the arm will then determine what cartridges will work well with that turntable/arm combination. Until you are spending a fair amount of money, many low compliance MC designs are not always suitable for use with the tonearm which is supplied with the table.
It is all about resonance which should lead you to get a recommendation from a reputable dealer. Frank has given very good information but it cannot cover the particulars of all arm/cartridge combinations. If possible, I would try to audtion the table/arm/cartridge combination before making a purchase.
Actually I disagree on one (minor) thing - sorry Max, I digress. The cartridge has to trace the groove, and in so doing it has to drag the arm along with it. Linear tracking arm or pivoted, the job is the same and performed by the cartridge. The arm and cartridge are meant to be strongly coupled (and in the case of the Graham Nightingale, they are one thing). It's the compliance in the cartridge that allows it to trace the groove while maintaining its journey across the record.
Then the analogy to the furrowed field would indicate the plow is dragging the worker across the field. Not much work will get done with that arrangement.
Indeed. That analogy is to give people an idea of the relative amount of work being done. The fact is that the actual energy used to drive the groove is done by the platter and motor. That's what makes the cartridge move. But the idea of the football field rotating at 33rpm just doesn't square up in my head...
The point of the analogy is to show the relative sizes of the stylus/arm in human terms to give an appreciation of the mammoth task involved.
Yes, I understand that part. How about if we extend the analogy to a record groove being the furrow and the movement past the stylus is the movement of the earth. Now, if we straighten out the groove to one long furrow (which gets us to; how many grooves are there on one side of a record?) what is the cartridge doing in relation to the tonearm? We have to have a tonearm that is able to negotiate any variations in the furrow (warps or off center) while holding the cartridge's stylus centered and perpendicular to the record groove.
The problem with many linear tracking arms is they are designed so either the tonearm is dragging the cartridge or the cartidge is dragging the tonearm. Usually a combination of both all the way across the record.
It's the cantilever and its suspension that follows the furrow. In extreme cases the arm may have to compensate for record warp, but this has nothign to do with the furrow itself.
The cartridge body is meant to seem stationary in relation to the mount (or pivot if MM) point of the cantilever. If you did unwind the furrow so it went around the earth, the arm could be engineered to be fixed apart from up and down movement so the cartridge could negotiate the mountains and valleys. Since the furrow is moving in a straight line, the arm does not need to have side-side movement.
But this is getting beside the point. Any arm, be it linear or not is dragged by the cartridge. Even airpump arms are only designed to overcome their friction and allow the cartridge to pull them across the record surface.
Hi. This is a (sort of) follow up to Max's original question: how do you tell whether you have a MM or MC cartridge? Is it simply that if I can change the stylus it's a MM? I have an old, but serviceable, Fisher MT6330 turntable that has a label saying 'Replacement Stylus ST35-VD'. Finally, if I buy a new stylus, is it simply a matter of levering off the old one and 'clicking' the new one into place (I lost the manual for the turntable years ago!).
The way you know which you own is to know which you own. Sorry, but that's what it amounts to. I have never encountered a MC with a replaceable stylus assembly. But I have encountered a MM with a nonreplaceable stylus assembly. For the most part though, yes, if you can replace the stylus, you have a MM cartridge. And, yes, how it comes off is how it goes back on. Some pull down, some at an angle and some straight out.