Trevor Wilson said

I took the question to be general. Do you mean that it is obvious that MC has
less inductance than MM? Why is that please?

**MUCH less wire in the coils (to keep moving mass within reasonable limits).
High output MC carts negate many of these advantages.

I see, although the restriction may have more to do with space than weight. But
it is possible to have low output MM with low inductance, or high output MC with
high inductance. Similarly, all magnets are not by definition heavier than all
coils. What is not simple is how the process of optimisation led MM and MC to be
so different in practice.

I know nothing of cartridges and the last one I heard was in a Dansette, but
there are other machines similarly categorised, such as ammeters and generators.
I remember the change from MC dynamos to MM alternators, which had much greater
output for a similar size and weight. Initially they were unreliable on
motorcycles because their extra rate of work had not been taken into account
properly, mechanically and thermally.

MM meters are generally not linear, if I remember, because the magnetic field is
not constant over the travel of the coil. With a moving coil, you can have a
magnet with a hole in it, or two magnets, or a ring magnet with a gap, with a
much more constant field in the space between, in which a small coil can move.
It would be impractical to have such a magnet assembly as the moving part.

A problem for MC dynamos is the need for commutator or slip-rings. A MC
cartridge with two coils needs at least three connections brought to a
stationary point, with attendant compromises in suspension.

I assume MM cartridges were initially high output, simple, cheap, not very
linear, and had a high mechanical impedance. MC were the opposite in all
respects. Advances in magnetic materials and their fabrication, and
smaller-scale boutique production, will have allowed carts to use more complex
and lighter magnets, and hence MM with more linearity, and MC with larger coils
perhaps? Or how else is linearity and high output achieved simultaneously?

Does one tend to have more crosstalk than the other?

BTW, has anyone mentioned the problem of noise in the early stages of
amplification from a low output source? Largely solved now, perhaps, but it was
a real problem during most of the development of cartridges.

cheers, Ian






"Trevor Wilson" wrote in message
...

"Ian Iveson" wrote in message
. uk...
Trevor Wilson ventured

**Er, not quite. The FR plots of MC carts, in some cases, CAN be shown to be
superior. The reason, of course, is blindingly simple. It's all about
inductance. The inductance of (LOW OUTPUT) MC carts is very low, indeed.
This enables them to produce a very flat, very wide (up to around 60kHz)
frequency response, with a correspondingly superior rise time. The real
benefit of such a system is that LC resonance effects are often well outside
the audible range. This means that a low output MC cart may exhibit a very
flat phase response within the audio band. This may not be the case with
high output MC carts nor with some MM carts.

Are you sure "blindingly simple" makes sense?


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