The Cartridge - The Assembly

An electromagnetic generator otherwise known as a cartridge, can be divided into 4 separate sections.

(1) Physical

Cartridge Body, Cartridge Weight, Cartridge Size

(2) Mechanical

Stylus Type, Stylus Radius, Cantilever Material, Tracking Force, Tracking Ability, Compliance,

Resonant Frequency, Desired Resonant Frequency

(3) Electrical

Cartridge Type, Cartridge Output Voltage, Cartridge Output Impedance, Phono Stage Load Impedance / Resistance, 

Phono Stage Load Capacitance

(4) Audio

Frequency Response, Channel Balance, Channel Separation

The following is a full description of each section:

(1) Physical 

Cartridge Body Material 

The material used to form the body or frame of the cartridge can be manufactured using moulded plastic, CNC machined aluminium, and in some very high end cartridges exotic woods or semi precious stones.

The various materials used all have different resonance and vibrational responses which effect the tonal characteristics of the cartridge.

Cartridge Weight 

The overall weight of the cartridge needs to be considered when matching the cartridge with a tonearm. Matching the right cartridge with the right tonearm is important as not all cartridges work with all tonearms and vice versa.

The mechanical specifications of the cartridge and the tonearm need to be considered to obtain a good match. The reason for this is the overall weight of the cartridge and tonearm, plus the cartridges mechanical compliance value dictates the resonant frequency of the cartridge/tonearm combination.This resonance is caused by the combination of the cartridges stylus / cantilever assembly spring like tension and weight of the tone arm, as with everything vinyl, it’s all about resonance and vibrations.

(See notes with regard to Cartridge Compliance)

Cartridge Size

Also of note is the size of the cartridge body, does the tone arm allow you to adjust the height of the tone arm to accommodate large size cartridges with regard to VTA (Vertical Tracking Angle) plus allow Azimuth adjustment.

(2) Mechanical 

The stylus and cantilever assembly constitute the mechanical section of the cartridge. 

Groove vibrations are picked up by the stylus tip, which resonate along the cantilever / magnet or cantilever / coil assembly causing the overall assembly to vibrate at its pivot point and create an electrical signal.

Stylus Type

This specification indicates if the stylus is a bonded or nude type and what shape the stylus tip is:

Conical, Elliptical, Hyper Elliptical, Line Contact, Shibata, or MicroLine.

(See Hifiology Stylus Notes)

Stylus Radius

Conical / Spherical, Elliptical, Hyper Elliptical, Line Contact, Shibata, or MicroLine all have varying Stylus Radii.

The variation is what makes each stylus type unique.

A Conical / Spherical stylus due to its semi circular shape has one radius. This stylus shape offers less tip and groove wear but unfortunately a reduced high frequency response.

From the Elliptical to the MicroLine, each stylus has a front and side radius.

The front radius being wider than the side radius. 

The specifications are indicated for example as follows: 

R1 0.2 x R2 0.7 mil

R1 represents the side radius, when the stylus is viewed from the side and R2 the front radius, when the stylus is viewed from the front. 

Utilising a smaller side radius with a reduced front to rear groove contact point, the stylus offers improved accuracy when reproducing higher frequencies.

The unique range of stylus tips track the records groove with increased precision, reduced distortion plus improved frequency and phase response

Cantilever Material

The Cantilever can be made of Aluminium, Boron, Zirconia, Sapphire, Ruby and Diamond.

All these materials offer various qualities of resonance and transmission of vibrations from the stylus tip, reproducing the vibrations in the record groove with varying degrees of precision, accuracy, speed, and fidelity.

Tracking Force 

The manufacturers recommended Vertical Tracking Force 

(See Hifiology Stylus Notes)

Tracking ability at 315 Hz at recommended tracking force: 

How well the stylus tracks the records groove at the recommend vertical tracking force when subjected to the vibrations of a test signal of 315 Hz recorded within the test records groove.

When choosing a cartridge to correctly match with your tonearm the following specifications need to be consider:

  1. The Compliance value of the cartridge.
  2. The weight of the cartridge including mounting screws and washers.
  3. The weight of the tone arm.
  4. The Resonant Frequency of the the stylus / cantilever / suspension assembly.

The Compliance value plus the Effective Mass or total weight of the cartridge and tonearm all dictate the Resonant frequency of the stylus / cantilever / suspension assembly. 

Compliance 

Think of a spring which has a specific amount of coiled tension, some springs are tight and some are loose. The stylus / cantilever / suspension assembly acts in a similar way to a spring, in that it moves up and down with a specific amount of tension whilst suspended within and at its pivot point. 

This specific tension, which is either tight of loose is known as its mechanical compliance value, described as µm/mN - (Micrometer - Micron / Micronewton)

A High-compliance cartridge (35µm/mN) matches well with a Light weight tonearm, 10grams or lower. 

A Mid compliance cartridge (10 to 20 µm/mN) matches well with a Middle weight tonearm, 10grams or higher.

A Low - Compliance cartridge (5 to 10 µm/mN) matches well with a Heavy weight tonearm, 25grams or higher.

Resonant Frequency of the stylus / cantilever / suspension assembly

The Compliance value plus the Effective Mass or total weight of the cartridge and tonearm all dictate the resonant frequency of the stylus / cantilever / suspension assembly.

Desired Resonant Frequency Range

A resonant frequency between 7Hz to 12Hz & 10Hz to 14Hz is favoured by some, whilst others prefer 9Hz to 11Hz as the desired range.

A Light Weight tone arm fitted with a cartridge with a Low Compliance value results in a resonant frequency above the desired range this affects the ability of the stylus to precisely track the records groove.

A Heavy Weight tone arm fitted with a cartridge with a High Compliance value results in a resonant frequency below the desired range exaggerating the effects of record warps and rumble produced by the turntable.

Some cartridges transmit a lot of vibrational energy into the tone arm. A tonearm with a good structural bearing or uni-pivitol design will dissipate this energy. Some tonearm designs allow you to further dampen the arms vibrations using a viscous silicone fluid. 

To calculate the Resonant Frequency of the combined cartridge and tonearm you can use the following formula: 

1000/[6.28*square root (M*C)) 

M = Weight of the cartridge plus the total weight of the tonearm (Example 14 grams)

= The cartridges mechanical compliance value. (Example 15 µm/mN)

Example: 1000/[6.28*square root (14*15))

If you are not a mathematician copy the formula inserted with your specific M and C values and paste or type into Google search the following:

Calculate 1000/[6.28*square root (14*15))

The answer is 10.9883050851

Resonant Frequency = 10.99Hz

resonance-graph-the-listening-suite.jpg

(3) Electrical  

As the cantilever / magnet or cantilever / coil assembly vibrates between the cartridges main magnets or coils it creates an electrical signal which varies in voltage depending upon the type of cartridge.

Cartridge Type

Moving Magnet or Moving Coil

Cartridge Output Voltage

The output voltage of the magnet or coil assembly measured in microvolts (μV)

Cartridge Output Impedance 

The output impedance of the magnet or coil assembly measured in microohms (Ωohms)

Phono Stage Load Impedance / Resistance 

For Moving Magnet set to 47 kOhm, For Moving Coil set to 100ohms

Phono Stage Load Capacitance

The Cartridge manufactures recommended Capacitance setting measured in picofarads (pF) 

Example of Moving Magnet Electrical Specifications

Output Voltage: 5.5 mV

Cartridge Impedance:

Phono Stage Settings for a Moving Magnet Cartridge

Load Impedance / Resistance: 47KΩ ohms

Capacitance: 0 - 50pF - 100pF - 150pF - 200pF - 250pF - 300pF - 350pF - 400pF - 450pF - 500pF - 550pF - 600pF - 650pF - 700pF (Picofarads)

Phono Stage Gain Settings

Gain: 10dB - 20dB - 30dB - 40dB - 50dB - 60dB - 70dB

Examples of Moving Coil Electrical Specifications

High Output Moving Coil 

Output Voltage: 2.8 millivolts 

Cartridge Impedance: 1000ohm

Phono Stage Settings

Impedance / Resistance: See cartridge manufactures recommended settings measured in Ωohms

Low Output Moving Coil  

Output Voltage: 0.3millivolts to 0.7millivolts

Cartridge Impedance: 5 ohms - 32 ohms

Phono Stage Settings for a Moving Coil Cartridge

Impedance / Resistance: 100Ω ohms

Resistive load: 

-010-020-030-040-050-060-070-080-090-100

-110-120-130-140-150-160-170-180-190-200

-210-220-230-240-250-260-270-280-290-300

-310-320-330-340-350-360-370-380-390-400

-410-420-430-440-450-460-470-480-490-500                     

-510-520-530-540-550-560-570-580-590-600

-610-620-630-640-650-660-670-680-690-700

-710-720-730-740-750-760-770-780-790-800

-810-820-830-840-850-860-870-880-890-900

-910-920-930-940-950-960-970-980-990-1000Ω

Phono Stage Gain Settings

Gain: 10dB - 20dB - 30dB - 40dB - 50dB - 60dB - 70dB

Step-Up Transformer 

A Low Output Moving Coil cartridge has both a Low Output Voltage and Low Output Impedance.

Using a Step-Up transformer raises the output voltage of the cartridge and sets the required impedance between the cartridge and the phono stage.

Note:

Impedance 

Is the reduction of current flow in an Alternating Current circuit which is specified in Ohms.

Resistance 

Is the reduction of current flow in a Direct Current circuit which is specified in Ohms.

Capacitance  

Capacitance is the ability of a component to collect and store energy in the form of an electrical charge.

The number of electrons it can hold under a set voltage is called its capacitance, expressed in pF (pico farads) 

(4) Audio

Frequency Response

This specification indicates the upper and lower range of frequencies that the cartridge operates within.

Channel Balance: ≥ μV

The channel balance specification of a cartridge expressed in microvolts (μV), 

indicates the cartridges ability to reproduce the Left and Right channels at equal output levels. 

Channel balance is frequency dependent and varies in μV, across the audio spectrum from 20Hz to 20,000Hz. 

The cartridges channel balance can be effected by the following cartridge alignment settings,

incorrect azimuth settings, misalignment of the tonearm plus its anti-skating adjustment.  

Channel Separation: ≥ dB

The amount of audio signal expressed in dB that crosses or bleeds from the Left Channel to the Right Channel and vice versa

Also known as Crosstalk, a low Crosstalk value indicates a high value of channel separation.

Channel separation is also frequency dependent and varies in dB across the audio spectrum from 20Hz to 20,000Hz. 

A high channel separation value can also improve the cartridges stereo image or soundstage presentation.