Everything you need to know about cartridges: Introduction

GRAMPHONE RECORDS – THE BEST MUSIC SOURCE

Few people are aware that gramophone records can be of a higher technical quality than even the most expensive tape recorders. On a record, it is possible to achieve a signal-to-noise ratio (the difference between the loudest and the softest sounds that can be recorded) of 70dB (3000 times).

Only very few tape recorders have such a high signal-to-noise ratio or dynamic range. The majority do not go beyond 60dB (1000 times). A record can have a frequency range that extends from 5Hz to 45,000Hz, which means that it is possible to reproduce the entire audible range – from 20Hz to 20,000Hz – correctly. It is often claimed that records have a relatively high level of distortion.

However, a well recorded and well cared for record can contain so little distortion that only a direct radio transmission will be of a higher sonic quality. (Fig. 1)

Fig. 1. The cutting of a gramophone record is an exacting process which requires high precision. Only a perfect pick up cartridge is able to track all the information engraved in the record groove.

IT IS THE CARTRIDGE THAT SETS THE LIMIT

It has often been said that a Hi Fi system can be compared to a chain that is no stronger than the weakest link. The loudspeakers are generally thought to be the components in a Hi Fi system that set the limit for the quality of sound attainable. However, it is worth noting that if the sound that is picked up from the record groove is not optimal, not even the very best loudspeakers will be able to improve reproduction.

The cartridge is all too often regarded as a fixed part of the turntable. The majority of consumers but their turntable with a cartridge that is included in the price, and many do not think about the importance of the role played by the cartridge in sound reproduction until it is either damaged or simply worn out. Most salesmen have to be price-conscious in order to keep up with competition, and when it comes to turntables, the only possibility of arriving at a reasonably attractive price is usually by compromising on some of the demands made of the accompanying cartridge. This means, quite often, that the quality of the cartridge does not match that of the tonearm/turntable or the remainder of the Hi Fi equipment with which it will be used.

Incompatibility between turntable and cartridge such as this prevents the amplifiers and speakers from giving their best performance. However, the problem cannot be solved merely by investing in a more expensive cartridge. Electro-acoustic research carried out in recent years has proved that certain conditions relating to the interplay between tonearm and cartridge must be fulfilled before optimal sound reproduction can be achieved.

IF THE CARTRIDGE IS NOT GOOD ENOUGH

It is not difficult to judge whether or not a cartridge is good enough for the associated Hi Fi equipment. All cartridges should be inspected at least once a year in a Hi Fi specialist shop, which has facilities for checking whether the diamond stylus is worn or whether there are other faults in the stylus unit. If on examination it is found that the stylus unit does need replacing, two possibilities exist. 1) a new, original stylus unit of the same type may be purchased, thus maintaining the same quality level as previously, or 2) investment in a new, modern cartridge may be made. The latter can be recommended in many cases as in relation to what it may otherwise cost to improve a Hi Fi system, the extra expenditure involved in the purchase of a really good cartridge must be considered one of the best investments that can be made in attaining better sound. The quality of the entire I Fi system will be increased considerably.

The disadvantages of an inferior cartridge are revealed in several different ways, the most irritating being distortion in the form of a raw and unpolished reproduction of the instruments, which makes listening over a longer period a tiring experience. Shrill violins and muddy piano tones are typical examples of too high distortion in the cartridge. An important characteristic in a cartridge is its ability to track the powerfully recorded passages on a record without jarring. A powerfully recorded piano can cause many cartridges to lose contact with the record groove, and the crackle that is heard is not only unpleasant to listen to, but it can also be damaging to the record groove. Thus, a cartridge with poor tracking ability can damage a record permanently after only one playing.

Another general disadvantage with poor quality cartridges is their inaccurate transient reproduction, i.e. their ability to reproduce the impulses in the music. Modern music with drums and percussion will soon reveal whether this particular cartridge characteristic is in order. If the cymbals sound too shrill, or on the other hand muffled, this is a sign of poor transient reproduction that more often than not can be improved by changing to a better cartridge. In the previous paragraphs we have talked a lot about quality, though without trying to put cartridges into price or quality groups. This would be pointless, as the cartridge in a Hi Fi system must be considered in relation to associated equipment. A cartridge giving a satisfactory performance together with a receiver and two speakers in the economy class may well have small faults that will be revealed ruthlessly if out into a system of very high quality. In other words, there must be a suitable match between cartridge and the associated Hi Fi equipment. As a guideline, the cartridge should cost between one-third and one-quarter the price of the complete turntable. In a typical Hi Fi system, the turntable would cost approximately one-quarter the price of the entire system. Therefore, in a system costing, say $1,000, the turntable would be $250 with the cartridge costing around $70.

Even with a cartridge of high quality, problems may arise if it is not compatible with the tonearm and turntable. A very common case of incompatibility is revealed in tis worst form when the volume is turned high and the entire system vibrates with a loud and constant hum. This phenomenon is known as acoustic feedback and may, for example, be caused by too high a compliance in the cartridge in relation to the tonearm’s mass. This mismatch will also be evident by the bass membranes of the loudspeakers, which will move out of beat with the music, giving an impure and muddy bass reproduction. In such cases, it is advisable to change to a lower compliance cartridge, although some older tonearms have such a high mass that they will create problems for practically all cartridges of contemporary design.

The latest Low Mass cartridges with their very low weight will, in many cases, help solve the problems of acoustic feedback when the correct compliance (relative to the mass of the tonearm) is chosen. Read more about this subject in the section “Choice of cartridge”.

HOW TO CHOOSE THE RIGHT CARTRIDGE

A new cartridge should match the turntable and the associated equipment; it should match the individual taste and, of course, the budget. Those who are primarily interested in good music and not part5icularly concerned about the technical side of Hi Fi would be advised to go to a Hi Fi specialist shop, where it will be possible to listen to different cartridges and receive expert advice. Those with Hi Fi as a hobby, wishing to discuss cartridges with Hi Fi specialists, can increase their knowledge by requesting brochures from the various cartridge manufacturers and by reading articles and test reports in Hi Fi magazines.

On the following pages, we will discuss cartridge principles, stylus types, and the most important technical specifications of the cartridges. We will also give hints on mounting, treatment and maintenance of cartridges. Information that is an invaluable supplement to cartridge brochures and articles.

THE TECHNIQUE BEHIND HI FI CARRIDGES

The function of the cartridge is to transform the undulations or little “wiggles” in the record groove to electrical oscillations, that are then amplified in an amplifier to finally draw the cones of the loudspeakers in the Hi Fi system.

Common to all cartridges is a diamond stylus that mechanically follows the record groove, transmitting its modulations - via a cantilever - to a miniature generator, which in turn transforms the mechanical movements into electrical currents. This may sound simple on the face of it and, in principle, it is. However, it must be borne in mind that a modern cartridge of high quality is the result of years of research and development combined with stringent production methods and quality control. It is a precision instrument which must accurately measure very small, very high speed motions in a delicate material. (Fig. 2.).

The Hi Fi enthusiast has the choice of dozens of cartridges with different operating principles and stylus types, which in turn can give the individual cartridge both advantages and disadvantages. It is impossible in a brochure such as this to cover all existing cartridges and our aim, therefore, is to describe the most important types in order to ease the choice for the consumer.

Fig. 2. Outline drawing of the cartridge principle. The cantilever transmits the information from the groove to a transducer, which transforms the mechanical movements into electrical signals.