This page lists the main terms used in the descriptions of phono cartridges and briefly describes the associated concepts. This list is not exhaustive, but rather includes the essential terms that you may come across in choosing and setting up a cartridge.
Alignment (of cartridge)
Ideally, the cantilever of the stylus should be parallel/tangential to the record groove. This is not possible over the entire record surface with a conventional pivoted tonearm, which traces an arc across the record, and requires a tangential or linear tracking arm, which traces a straight line across the record. However, a conventional tonearm that is over-hung (meaning long enough to over-shoot the central spindle) is able to achieve tangential tracking at two places on the record – these spots are called the ‘null points’. There are inner and outer null points. The locations of the two null points depend on the position of the cartridge in the headshell. Alignment of the cartridge is the process of locating it at a position that yields null points at the desired places on the record. Failure to achieve a good alignment of the cartridge may result in noticeable distortion, particularly in the inner grooves (towards the centre of the record). There is no one unique alignment solution – several alignment schemes are available, with names like Baerwald, Loefgren and Stevenson. The various alignment schemes yield similar results in terms of (slight) distortion in the outer grooves and differ most in the inner grooves. Sometimes, the turntable manufacturer gives guidance on cartridge alignment for their turntable by providing a tool that indicates where the stylus tip should be located (assuming the cartridge is ‘square’ in the headshell) – for this, they will have adopted one particular alignment scheme. If no tool is provided or you wish to adopt a particular alignment regime, you will need to use an alignment ‘protractor’, which you can purchase or can download to print on paper (downloadable from websites such as Vinyl Engine).
A conventional pivoted tonearm has a tendency to skate or skip towards the centre of a playing record. This effect arises because the tangent to the groove does not pass through the arm pivot and therefore the moving record pulling on the stylus produces a clockwise turning moment on the arm. Such tonearms are (usually) fitted with an anti-skating mechanism that produces an outward force to counteract this effect. The required anti-skating force depends on the tracking force and can be adjusted to accommodate different tracking forces. The anti-skating is calibrated such as that it should be set to the same value as the tracking force (e.g. a setting of 2 for a tracking force of 2g).
Balancing (the tonearm)
When a turntable is set up from new (or after transportation) or a new cartridge is fitted, the arm must be balanced and the required tracking force (and anti-skating) set. Before the tracking force can be set, the arm must be ‘zero-balanced’, which is the process of adjusting the position of the counter-weight (or other balancing mechanism) until the arm floats horizontally (has no tendency to move up or down). This is done to calibrate the tracking-force scale of the arm to zero in this state (the scale should be moved to zero without disturbing the counter-weight). The tracking force required for the cartridge/stylus can then be set (and the anti-skating set to the same value).
The cantilever is part of the stylus assembly, comprising a fine rod with the stylus at one end and a magnet (MM cartridge), piece of iron (MI cartridge) or pair of coils (MC cartridge) at the other end. The cantilever has a suspension and is made to vibrate by the act of the stylus tracing bumps in the record groove. The cantilever is often made of aluminium but can be made of carbon or, on expensive cartridges, boron or sapphire. The construction of the cantilever has a significant bearing on the sound and it must be rigid. A fine, light cantilever tends to be an indicator of a refined sound.
The capacitive load or load-capacitance is an important factor for Moving Magnet (MM) and Moving Iron (MI) cartridges – this capacitance is a key characteristic of the external electrical circuit presented to the cartridge on its pins. Normally, a recommended capacitive load is included in the cartridge specifications as a range – for example, 150-300pF.
The total capacitance has contributions from the phono pre-amp and the cabling between this unit and the cartridge. This cabling includes the internal tonearm wires and the cables between the arm and phono pre-amp. In the case of a phono pre-amp that is external to the turntable (the norm for vintage turntables), the capacitance contribution from the cabling is normally assumed to be in the region 150-200pF (note that low-capacitance cables must be used). The rest of the capacitive load comes from the phono pre-amp and the capacitance can be tailored to the cartridge by carefully selecting this component of the capacitance. Most phono pre-amps have fixed capacitance, with popular values being 100pF, 120pF, 200pF and 220pF, but the capacitance is selectable on more advanced units. Normally, the capacitance of an external phono pre-amp should be chosen such that the total capacitance (after adding in the cable capacitance) is within the cartridge manufacturer’s recommended range – for example, if the recommended range is 150-300pF and we assume the cable capacitance to be 175pF, we may choose a phono pre-amp capacitance of 100pF or 120pF to keep the total within this range, which will be 275pF or 295pF.
The effect of capacitive load on the sound can be very pronounced. If the capacitive load is too low for the cartridge, it may sound closed or even dull. If the capacitive load is too high for the cartridge, it may sound too bright or, going to higher capacitances, rolled-off and closed. The reason is as follows. The external electrical circuit attached to the cartridge has a resonance frequency (caused by the interplay of capacitance and inductance) – this corresponds to a peak or hump in the frequency spectrum followed by a roll-off (tail) at higher frequencies. At low capacitances, this peak may be at a frequency beyond the audible range. As the capacitances increases, the resonance frequency decreases and comes within the audible range, where its effects can be heard, usually as an emphasis in the higher frequencies. If the resonance frequency is well within the audible range, the roll-off which follows the peak may also be noticeable as a reduction in very high frequencies. Some cartridges sound their best with this resonance outside the audible range but others benefit from the high-frequency lift provided by the resonance peak. The capacitive load recommended by the cartridge manufacturer is usually a good guide but can sometimes be misleading – cartridges can also sound good outside of the advised range and (rarely) can even sound better outside of this range.
In a ceramic cartridge, as the stylus vibrates in the groove, the other end of the cantilever applies varying pressure to a ceramic or crystal material, causing the material to flex and generate a voltage (and current). The resulting output signal then needs to be passed through a phono-stage for equalisation. Ceramic cartridges are regarded as low-quality and are usually found on cheap or old record players. Any half-decent turntable will be fitted with a magnetic cartridge.
Compliance (of stylus)
The compliance of a cartridge is a property that relates to its stylus, notably to the suspension of the stylus cantilever. It is a measure of the springiness of the suspension, with high-compliance meaning a soft suspension and low-compliance meaning a stiff suspension. It is important to match the compliance of the cartridge to the effective mass of the tonearm that will accommodate the cartridge. A high-compliance cartridge should be used on a low-mass arm and a low-compliance cartridge on a high-mass arm. If there is a mismatch between the arm mass and cartridge compliance, the sound may suffer – for example, if a low-compliance cartridge is used on a light arm, the stiff suspension of the stylus may not properly absorb the large low-frequency vibrations from the groove, with these vibrations being transmitted into arm movements instead, resulting in a poorly defined bass.
The units of compliance are quoted in different ways – for example, µm/mN. This shows that compliance is a measure of movement (distance) per unit force. For convenience, the units are often quoted as ‘compliance unit’, represented by cu. Compliance is categorised as low, medium and high. According to the manufacturer Ortofon, the compliance categories operate as follows:
- Low-compliance: Less than or equal to 10 cu
- Medium-compliance: Between 10 cu and 20 cu
- High-compliance: Greater than or equal to 20 cu
The compliance of a stylus is usually published in the cartridge/stylus specifications by the manufacturer. Normally, the dynamic compliance (rather than static compliance) is the main one of interest. The vibrational frequency at which the compliance was measured is also normally quoted. This is usually 10Hz (and the above figures assume this) but Japanese manufacturers tend to use 100Hz. Therefore, in order to compare cartridges, it is necessary to convert a compliance quoted at 100Hz to the equivalent at 10Hz – the commonly employed conversion factor is around 1.75 (so a compliance of 8 cu at 100Hz converts to 14 cu at 10Hz).
The stylus compliance and effective mass of the arm (with cartridge) together determine the mechanical resonance frequency of the arm/cartridge system, which may be important to consider. For more information on arm/cartridge matching, refer to the entries on Effective Mass and Resonance Frequency.
A conical stylus (synonymous with spherical stylus) has a horizontal cross-section in the form of a circle. It is the most basic stylus profile and is generally found on cheaper cartridges. The signal from a conical stylus is more susceptible to distortion than more advanced stylus shapes (such as elliptical). The lifetime of a conical/spherical diamond stylus is usually assumed to be 300-400 hours of playback (although Audio Technica claim 500 hours on their website).
Effective Mass (of tonearm)
The effective mass of the tonearm is a key factor when choosing a cartridge, as it is important to match the cartridge compliance with the effective arm-mass in order to achieve a happy marriage between the two components. Firstly, the effective mass is not the total mass of the arm. It is the inertial mass that the tonearm effectively has at the position of the stylus tip (and is related to the lateral force at this point needed to accelerate it). However, it is calculated without a cartridge fitted to the arm. There is no need to know how to calculate effective mass but it is interesting to note that the elements furthest from the tonearm’s pivot make the largest contribution. Also, adding/subtracting mass in the vicinity of the headshell results in a change in the effective mass of around the same magnitude.
The effective masses of tonearms are generally divided into three categories: low, medium and high. According to the manufacturer Ortofon, the categories operate as follows:
- Low-mass: Less than or equal to 10g
- Medium-mass: Between 10g and 25g
- High-mass: Greater than or equal to 25g
The effective mass of a tonearm is often published by the tonearm or turntable manufacturer in the product specifications. It usually includes the mass of the headshell but not the mass of the cartridge.
Generally, low-mass arms should be used with high-compliance cartridges and high-mass arms should be used with low-compliance cartridges. That leaves medium-mass arms to be used with medium-compliance cartridges, but there is usually some flexibility – for example, a high-compliance cartridge often works well with an arm towards the light end of medium-mass. For more information on arm/cartridge matching, refer to the entries on Compliance and Resonance Frequency.
An elliptical stylus is generally formed from a conical/spherical stylus with front and back parts cut away to reduce its depth (along the groove). This results in a smaller ‘horizontal’ contact length and a larger ‘vertical’ contact length with the groove wall than for a conical/spherical stylus. As such, it is able to more accurately retrieve information from the groove (with less distortion). Elliptical styli are found on cartridges from low-end to high-end. They can have profiles of different eccentricities – the sharper profiles are found on more expensive cartridges and a very fine elliptical stylus is often referred to as hyper-elliptical. The lifetime of an elliptical diamond stylus is usually assumed to be 700-800 hours of playback (although Audio Technica claim only 300 hours on their website).
Gain (of phono pre-amp)
The gain of a phono pre-amp is a measure of the amplification it provides in boosting the weak signal from a magnetic cartridge to the level required for a normal line input of an amplifier. It is quoted on the non-linear scale of decibels (dB), which is logarithmic (base 10). The gain is normally included in the specifications of a phono pre-amp. For an MM/MI cartridge, a value of 40dB or higher is ideal. An MC cartridge requires a higher gain and a value of 55dB or higher is typical. Sometimes the gain is not quoted but an input voltage Vi and output voltage Vo are given, in which case the gain can be calculated as 20Log(Vo/Vi).
The headshell is the part of the tonearm that accommodates the cartridge. The headshell includes four colour-coded wires that attach to the cartridge pins. It also usually includes a pair of slots to accommodate the screws with which the cartridge is attached. Slots are used rather than holes to allow the cartridge to be appropriately positioned in the headshell for the particular turntable – the process of achieving the optimum location is known as alignment. Depending on the arm, the headshell may be a fixed part of the arm or be detachable. A common type of detachable headshell has the standard ‘SME type’ connection to the arm, which makes it is easy to attach and detach – these SME-type headshells are usually used on S-shaped and J-shaped arms (but not straight arms). Spare headshells can be bought separately and are available in different styles, colours, materials and masses.
A magnetic cartridge works on the principle of electro-magnetic induction – an electrical current being induced in a wire by a changing magnetic field. There are three main varieties of magnetic cartridge: Moving Magnet (MM), Moving Iron (MI) and Moving Coil (MC). A magnetic cartridge tends to produce a smoother, fuller sound than the main alternative, a ceramic cartridge, and is found on all but the cheapest turntables.
Moving Coil (MC)
In a Moving Coil (MC) cartridge, a pair of induction coils is attached to the end of the stylus cantilever and, as the cantilever vibrates, moves around in the magnetic field produced by a fixed magnet. Electrical currents are induced in the coils and output from the cartridge. The output signal is extremely weak and needs to be passed through a special phono pre-amp of very large gain. MC cartridges tend to be expensive, starting at around £200. They seldom have replaceable styli, so when the stylus wears out, the cartridge must be sent away to be ‘re-tipped’ with a new stylus or replaced with a new cartridge.
Moving Iron (MI)
In a Moving Iron (MI) cartridge, a piece of iron is attached to the end of the stylus cantilever and, as the cantilever vibrates, moves around in the magnetic field produced by a fixed magnet. This movement perturbs the magnetic field which, in turn, induces electrical currents in a pair of fixed induction coils. The output signal is weak and needs to be passed through a phono pre-amp of the same type used for the more common MM cartridges. MI cartridges are also priced similarly to MM cartridges.
Moving Magnet (MM)
In a Moving Magnet (MM) cartridge, a magnet is attached to the end of the stylus cantilever and, as the cantilever vibrates, moves around between a pair of fixed induction coils. As a result of this movement, electrical currents are induced in the coils and output from the cartridge. The output signal is weak and needs to be passed through a special phono pre-amp. MM cartridges are the most common kind of magnetic cartridge and their prices range from about £15 to more than £1000. They are regarded as superior to non-magnetic cartridges, such as ceramic cartridges, but inferior to MC cartridges. A decent turntable will be fitted with an MM cartridge, at least.
Needle is old-speak for ‘stylus’ – most people today would use the word stylus. Refer to the entry for Stylus.
Output Level (of cartridge)
A cartridge produces a very weak electrical signal, which is usually measured in milli-Volts (mV). A Moving Magnet (MM) or Moving Iron (MI) cartridge typically produces a maximum output of 5mV, although figures vary from about 2.5mV to more than 7mV (higher outputs being common for DJ cartridges). A Moving Coil (MC) cartridge produces a much lower output, typically around 0.5mV. In all cases, the signal must be boosted by a phono pre-amp (also called a phono-stage) before it is passed to the amplifier for main amplification. Refer to the entry for Phono Pre-amp.
The phono pre-amp (aka phono-stage) is a unit that provides pre-amplification of the weak signal from a cartridge before it is passed to the amplifier for main amplification. The amplification factor of this pre-amp is known as the gain and is measured on a non-linear scale in decibels (dB). The phono pre-amp also has another vital function by providing an equalisation role. When a record is cut in the factory, the treble frequencies are emphasised. On playback, it is then necessary to de-emphasise the treble frequencies, which also has the effect of reducing the audible surface noise of the record, thus improving the signal-to-noise ratio. In addition, the low frequencies are de-emphasised on cutting and emphasised on playback. The most common equalisation method used is the RIAA (Recording Industry Association of America) scheme, but others also exist.
The phono pre-amp may be part of the amplifier (if the amplifier has an input marked “Phono”), be incorporated in the turntable (in which case a normal line input on the amplifier should be used) or be a separate unit that exists between the turntable and amplifier (these tend to be better-quality units). Note that MM/MI cartridge and MC cartridges require different levels of amplification (gains) and therefore different phono pre-amps (although units exist containing circuits for both MM/MI and MC cartridges).
The circuit of the phono pre-amp contributes capacitance to the capacitive load of the cartridge and the magnitude of this capacitance can affect the balance of the sound, notably for an MM/MI cartridge (while the impedance of the unit is an important factor for an MC cartridge). The capacitance value of a phono pre-amp is usually published in the manufacturer’s specifications for the unit. Some phono pre-amps have variable capacitance to allow the capacitive load to be matched to the requirements of the cartridge. Refer to the entry on Capacitive Load for more information.
Phono-stage is an alternative name for a phono pre-amp circuit. Refer to the entry for Phono Pre-amp.
Pins (of cartridge)
A cartridge usually has four pins at its rear for connection to the headshell of the turntable’s tonearm. The connections are colour-coded (usually shown on the headshell wires and sometimes on the cartridge) as follows:
- White: Left Channel Positive (L+)
- Blue: Left Channel Ground (LG)
- Red: Right Channel Positive (R+)
- Green: Right Channel Ground (RG)
Care should be taken to make the correct connections. The contacts must also be tight – use narrow-nose pliers to squeeze the wire tags over the pins, if necessary.
Resonance Frequency (of tonearm/cartridge/stylus)
The tonearm and cartridge/stylus form a mechanical system that can be considered as a rod pivoted at one end and with a spring at the other end (the stylus). This system will have a natural frequency of vibration – its resonance frequency. If vibrations close to this resonance frequency from an external source reach the system, it will vibrate in sympathy or resonate, and this resonance may become uncontrollable. The resonance frequency depends on a number of factors including the effective mass of the arm and the compliance (springiness) of the stylus. The resonance frequency cannot be avoided but should be chosen in a place where it can do least harm. The most acceptable value is usually taken to be in the range 7-12Hz.
If the resonance frequency is below 7Hz (by using a high-compliance cartridge on a high-mass arm), warped records may become a problem – a kink in the record may generate mechanical harmonics of a few Hz and if one roughly coincides with the resonance frequency, the stylus may have difficulty staying in the groove.
If the resonance frequency is above 12Hz (by using a low-compliance cartridge on a low-mass arm), this is approaching the audible range and resonance effects may be heard in the sound.
Therefore, a cartridge should be chosen with a stylus compliance that together with the effective arm-mass gives a resonance frequency in the range 7-12Hz (the cartridge mass must be included in the effective mass for this calculation). The resonance frequency can be easily obtained using an online resonance calculator, such as the one on the Vinyl Engine website. For more information on arm/cartridge compatibility, also refer to the entries for Compliance and Effective Mass.
A spherical stylus (synonymous with conical stylus) has a lateral cross-section in the form of a circle. It is the most basic stylus profile and is generally found on cheaper cartridges. The signal from a spherical stylus is more susceptible to distortion than more advanced stylus shapes (such as elliptical). The lifetime of a spherical/conical diamond stylus is usually assumed to be 300-400 hours of playback (although Audio Technica claim 500 hours on their website).
The term stylus is synonymous with ‘needle’. It is a sharp piece of precisely shaped material that makes contact with the record groove (sitting between the groove walls) and vibrates as it tracks along the groove. On the cartridge, the stylus is attached to the exposed end of the cantilever and causes the cantilever to vibrate. The stylus is made of a hardwearing material, usually diamond but sometimes sapphire on the ceramic cartridges of very cheap or old record players. A stylus may be constructed from a single shaft of diamond, which is known as a ‘nude’ diamond stylus. Alternatively, a stylus may have a diamond tip bonded to a metal stub or shank, which is known as a ‘bonded’ diamond stylus. Nude styli are preferable to bonded styli, as they have no material interface and generally have a lower tip mass, but they are more expensive. The stylus tip has a particular ‘profile’, the most basic being conical or spherical (which are equivalent), but a stylus with an elliptical profile extracts information from the groove more accurately. Further, more elaborate profiles are offered on the more up-market cartridges.
Vertical Tracking Force (VTF)
The tracking force is the downward force, expressed in grams, that the stylus exerts on the record. A stylus will always have a recommended tracking force value or range. Using a value outside of the recommended range could result in undue wear on the stylus and on the records, and even result in damage to the stylus suspension. The mid-point of the tracking force range is often (but not always) quoted as the normal value – so for a range of 1.25g to 1.75g, the recommended value may be 1.5g. However, it is sometimes considered wise to use a tracking force in the top half of the recommended range in order to ensure that the stylus is secure in the groove and therefore avoid mis-tracking that may damage the groove. In order to set the tracking force for a newly installed cartridge, it is first necessary to balance the tonearm horizontally (usually by moving the arm’s counter-weight) in order to achieve a tracking force of zero – the desired tracking force can then be set (usually by moving the counter-weight inwards towards the pivot).