How does the Stanton 680 cartridge operate?

This cartridge sounds very nice.


This is a summary on what was understood by starting reading the Stanton patent, US3546399.


There are great similarities to a single ended amplifier with output transformer, to a ribbon microphone, to a condenser microphone.


Here is how:


Abstract:
Coil is stationary.
Magnet is stationary.
It is only the tiny stylus cantilever that moves through a magnetic field.


There is a coil. Very like a transformer with one winding.
This coil is the output of the cartridge.
There are magnetic materials creating a magnetic field conductive path which passes through the coil. Very like laminations we use on transformers.
But this path consists of magnetic permeable material (pole pieces) in series with a permanent magnet in series with a tiny moving magnetically conductive element which is a part inside the stylus cylinder assembly.
This is the only non stationary element, it moves with the music signal on record, faithfully as it has very low mass.
The change in magnetic flux creates an EMF by Faraday's induction law on the coil.
So we get the output music voltage signal.


So it is like a single ended class A amplifier where the electron tube changes the current through the primary of output transformer.


It is like a ribbon microphone where a ribbon of aluminum which conducts an Electric field vibrates inside a magnetic field.
The analogy on the cartridge is that only a small thin of Magnetically conductive wire vibrates to the music signal. It conducts the Magnetic field.
On a ribbon microphone we out the output form the secondary of a transformer.
Such a transformer already exists in this record playing cartridge as explained above.


It is also like a condenser microphone.
On a condenser microphone there is a source of EMF (the polarizing voltage, or electret material electric potential is cases of electret capsules).
The electric circuit is completed by a series resistor where the output voltage is created before feeding a FET or electron tube.
Here in the cartridge there is a permanent stationary magnet which creates the MMF (magneto motive force). The magnetic circuit is completed by magnetic material (conductors of magnetic field) in series with a moving conductor of magnetic field.
On the condenser capsule the change of capacitance by music creates a changing voltage drop at the resistor.
On the cartridge the change of inductance by music creates a changing MMF drop in the magnetic circuit.
The coil converts a changing magnetic field to a changing electric field. In fact a changing magnetic field automaticaly creates a changing electric field (electromagnetic theory). We get the voltage music output from the ends of the coil.


There is another such transformer coil structure for the other channel ie for stereo.
The magnetic fields are at 90o. Each B in in an inclination of 45o, like Blumlein microphone pairs.
Actually the 90o magnetic field pairs are invented by Blumlein too for the purpose of stereo disc recording.


There is also the obvious similarly to electric guitar pickups.


See also:


Patents referred to in the Stanton patent, such as the Blumlein patent.


The Pickering Patent
US2538164


Feynman Lectures on Physics - Feynman, Leighton, Sands