Fri. Oct 23rd, 2020

Audio: Turntables |1978-4-10

Turntable

The phonograph has changed considerably since Thomas Edison recorded Mary had a Little Lamb over 100 years ago. Today, the turntable is the most popular and widely used piece of audio hardware, since records are still the most economical means of marketing music.

There are many different types of turntables, many with belt drive, direct drive or rim drive. All offer automatic, semiautomatic, or manual tonearm operations. With such variety, deciding which one to buy can be a bit difficult. The most popular tonearm used by today’s precision-conscious hi-fi buffs is the manual. Some people even purchase the tonearm separately and install it on a turntable base. On the other hand, many prefer automatic turntables. With these, the tonearm is activated by a single lever or button. And owners can stack two or more records to be played sequentially on some automatic record changers.

While most audio purists believe stacking damages the record’s playing surface; the fact is that records have a raised center and outer edge that prevents the playing surfaces from making contact. Recently BSR introduced a multiple-play turntable that gently lowers records onto the platter with an accuglide system.

When shopping for a turntable, the drive system is an important consideration. Each drive system has advantages and disadvantages. With belt drive, the platter is propelled by a pulley belt that’s rotated by a motor. The motor generally is a high-speed type; and in better models, a slower speed, servo controlled type. These offer greater overall speed accuracy. In most belt drive systems speed selection is accomplished mechanically — the belt is repositioned on the motor’s slotted drive pulley by a speed change lever. Unfortunately, the belt is subject to twisting and pulling while changing speeds. Belt drive turntables such as Philips, Technics, and Thorens offer electronic speed selection and reduced belt wear.

Turn Table — accuglide system
Turntable — Accuglide System

Rim drive is used in record changers when high torque motors provide power for the platter and changer mechanism. In rim drive, the motor spindle has a rubber drive wheel that runs along the inside edge of the platter, providing the necessary rotation. In both belt and rim, external motor vibration can easily be isolated from the platter. If vibrations reach the platter, they transmit unwanted signals through the tonearm assembly, resulting in acoustic feed back or “howling.” This is a common occurrence in discotheques if the turntable is exposed to speakers playing at exceptionally high sound pressure levels.

In the direct drive system, pulley belts and rubber drive wheels have been eliminated, along with the problem of belt wear. With this system, the platter is coupled directly to the motor, making it an integral part of the drive system. The record spindle is actually the motor’s drive shaft; the platter is the flywheel.

Technics introduced the first direct drive turntable, the SP-10. These turntables have become very popular because they offer unmatched speed, accuracy and incredible low wow and flutter. [Wow is a slow, repeating deviation in speed. Flutter results from fast and irregular changes in speed. Both can distort tonal quality.] No turntable is complete without a phono cartridge and a stylus. Without these, there would be no way to translate the undulations in the record grooves into electrical signals for playback. With this important task to perform, there should be no skimping on quality. If so, all other links in the hi-fi chain will suffer.

There are two types of phono cartridges: ceramic and magnetic Both can be purchased with either a diamond or sapphire stylus. Ceramic cartridges are generally used in less expensive turntables, often found in compact stereo systems. This cartridge often has a flip-over stylus, one for playing LPs and 45s, the other for the older 78 RPM records. However, magnetic cartridges are better in quality than the ceramic. For good sound reproduction, buy a magnetic cartridge with a diamond stylus, which lasts far longer than the sapphire. Empire, Pickering, Shure, and Stanton are some of the better cartridge manufacturers.

Keep reading this issue – next article

See a list of all archived Routes editions