A Guide to Turntable, Tonearm and Cartridge Specifications

Continuing on with our extensive vinyl series, the below is a guide to the majority of turntable specifications. It is important to note that while most of these specifications will be quoted by a manufacturer, not all manufacturers (Rega for example) choose to quote them. While specs can serve as useful guidance, lack of available specifications doesn’t necessarily mean a model should be dismissed.

Tonearm Specifications

Effective Length

The effective length of the tonearm is the sum of the mounting distance (the distance between the centre of the turntable spindle and the pivot point of the arm) and the stylus overhang (the distance between the stylus tip and the centre of the spindle were the cartridge positioned directly over the spindle).

Effective Mass

The effective mass is the mass of the tonearm, including the headshell, seen by the stylus. A mass of 10 grams or lower is considered a low mass arm. A mass of 11-25 grams is considered moderate mass, and an arm rated at above 25 grams is considered high mass.

Turntable Specifications

Arm Operation

When researching a turntable, you may come across a specification often called “operation” or “turntable type”. Common types are manual, semi-automatic, and fully automatic. The operation specification refers to the operation of the turntable’s tonearm.

A manual turntable requires that the arm be placed manually in the groove of the record, and lifted again at the end. A semi-automatic, sometimes known as an auto-return turntable requires that the arm be manually placed on the record, but will automatically raise the arm and usually return it to its rest when the inner-most groove of the record is reached.

A fully automatic turntable will provide a means to automatically place the arm at the start of a record, and will return the arm to the rest once the side is over. They usually feature a selector to choose the size of the record being played (7″, 10″ or 12″), though some feature a system of sensors to detect the record size.

While automatic turntables used to be extremely common, most turntables on the market today are manual designs though there are some exceptions. A manual turntable is much simpler mechanically, and there are no parts which have the potential to disrupt the free movement of the arm as it tracks the record.

Wow and Flutter

Wow is a term used to describe slow variations in the pitch of the sound, usually caused by uneven rotation of the turntable. Flutter is a term used to describe rapid variations in pitch, usually caused by uneven rotation of the turntable drive mechanism. Sometimes referred to as speed deviation or speed variation, wow and flutter is measured as a percentage where lower numbers are better.

Rumble

Rumble is the sum of the noise generated by the mechanical parts of the turntable which can be picked up by the stylus as it tracks the record groove. Rumble can be caused by the vibrating turntable motor, the turntable bearing, and any other components in the turntable’s drive mechanism. In general, the less rumble, the more musical detail you’ll hear. Rumble is measured in decibels, a typical example being -78dB (the quoted figure of a Technics SL-1200 turntable). In general lower numbers are better, though any well designed modern turntable will produce rumble far below the noise level of even the quietest vinyl pressing.

Speed

A typical turntable offers 2 playback speeds, 33.3 and 45 revolutions per minute (RPM). Usually long playing (LP) albums are played back at 33.3RPM, while singles (7”, 10″ and 12”) are played back at 45 RPM. Of course there are exceptions to this rule, with some albums being pressed at 45RPM as the faster speed offers better sound quality at the expense of shorter playing time on each side.

Before the introduction of 33.3 and 45RPM records, most records were played at 78 RPM. However not all 78 run exactly at 78RPM, many of them cut at speeds ranging between 70 and 100RPM. 16.2/3 RPM records also exist as do 8.1/3 RPM disks though both are far less common and finding a new turntable to play them is almost impossible, besides specialist hardware designed specifically for the preservation of the content contained on these records.

Cartridge Specifications

Channel Balance

The channel balance specification refers to the equal volume of both channels. Measured in decibels (dB), lower numbers result in a more equal balance between the left and right stereo channels, and therefore a more consistent and even stereo image.

Channel Separation

The channel separation specification, again measured in decibels (dB) equals the amount of separation between the left and right stereo channels. A lower separation figure results in a narrower stereo image, and 0 separation would result in the 2 channels being mixed, producing a monaural signal. Humans manage only 20DB of separation or so between our ears, so while common figures of around 25-30dB may seem extremely poor compared to other sources, it is in practice perfectly adequate.

Compliance

The compliance specification shows the compliance (springiness) of the stylus suspension. It’s usually measured in um/mN, where a rating of 5-10 is considered very low, 10-20 is moderate, 20-35 is high and 35+ is very high. It may also be measured in l0ˉ6 where 12 x l0ˉ6 or below is considered low compliance and between 13 l0ˉ6 and 25 l0ˉ6 is considered high to very high.

Along with the effective mass of the tonearm, the compliance will determine the low frequency resonance of the arm and cartridge. At the resonance point, the arm/cartridge combination produces a dramatic rise in output, an increase of 3-6dB or more is not uncommon. If this resonance frequency occurs in the region of recorded music (above 20Hz) or where rumble and record warps are problematic (<5Hz), the lower bass frequencies may be negatively affected, the audibility and speaker excursion of warps and rumble exacerbated, or in extreme cases the stylus will jump out of the record groove. In general, many cartridges and arms will mate well together and you’re unlikely to encounter any extreme compliance issues. Low mass arms mate well with moderately high and very high compliance cartridges, while moderate mass tonearms mate well with low compliance cartridges. To calculate the resonance frequency of your tonearm / cartridge combination, you can use the formula Resonant Frequency = 1000/[6.28*square root (M*C)] where M is the mass of the arm and cartridge and C is the compliance of the cartridge. For example, an arm/cartridge with a combined mass of 18g, and a cartridge with a compliance of 22 would yield a resonant frequency of 8.392Hz. A resonant frequency somewhere between 10-14Hz is ideal, but between 8 and 17Hz is usually acceptable.

Effective Tip Mass

The Effective Tip Mass is the weight of the stylus tip, cantilever and the element on the opposing end of the cantilever, be it the magnet, iron or coils. Measured in milligrams, the lower the number, the better the cartridge will track the high-frequency modulations in the groove. Lower numbers are therefore better, though any respectable hi-fi cartridge presently manufactured should have an acceptable tip mass.

Output Voltage

The output voltage specification shows the amount of electrical voltage output by the cartridge. It is measured by measuring the voltage as the cartridge reproduces a steady frequency (usually 1kHz) with the cartridge tracking the groove at 5 centimetres per second. The output voltage figure will enable you to match the cartridge to a phono stage. If your phono stage quotes a maximum input level in its specification, be sure that the output voltage of the cartridge does not exceed it. In vernal most MM cartridges will match with an MM phono stage, and most Macs will match with an MC stage. Too low an output voltage will simply result in lower overall volume.

Mounting

Over the years, a couple of standards have defined how a cartridge is mounted to the headshell of a tonearm. By far the most common mounting method is the half inch mount, and is the cartridge mount found in virtually any turntable made today. A cartridge is mounted using 2 bolts, the centres of which are exactly half an inch apart. The bolts pass through 2 slots in the headshell, designed to facilitate cartridge alignment, and attach the cartridge via a mounting hole at either side.

In the late 1970s, Technics devised a system known as the P Mount or T4P system. The P mount system was designed to remove the hassle from cartridge mounting as the specification dictated that all P Mount cartridges must weigh 6 grams, track at 1.25 grams and be manufactured such that the overhang was correct when inserted into a P mount arm. The cartridges could then be plugged into a P Mount tonearm and secured with a single screw at the side. The tracking weight, anti-skate, azimuth and all other parameters were preset to the values specified in the T4P specification.

The P mount system enjoyed huge success and was a great idea, though it sadly disappeared in the late 90s when the final turntables to use the standard ceased manufacture. These days there are no turntables being manufactured conforming to the P Mount standard, and only a couple of basic moving magnet cartridges.

This article is part of our Guide to Turntables and Vinyl series. Continue reading: Part 11, Turntable Drive Systems.