Understanding Turntables and Vinyl Playback
Turntables and Analog Stereo
Some people believe that all analog playback with an lp playing on a good turntable is the best readily available source of prerecorded music. They feel there is a harmonic richness, a “rightness” to the sound that is hard to beat. We are big fans of analog music and lp’s. There is more care and feeding involved with vinyl than with the digital formats. A turntable must be a stable platform that is resistant to airborne and structural vibrations. The cartridge must be properly mounted and aligned. It is an area where having a good dealer to assist you is invaluable. We, umm, know of such a dealer…
In many cases a separate phono stage is required. The signal on an lp record is tiny. When it is recorded the bass is intentionally rolled off to allow more playing time per side; low bass requires wider grooves. In addition the signal on the record is much, much lower in output than typical sources. A phono stage provides the reverse equalization needed to restore the bass. It also has a great deal of gain, or amplification, to bring the low level signal up to a level that is closer to that of other sources. After the advent of CD many preamplifiers and receivers quit providing this function, thus the need for an external device. One note of caution: Inputs marked CD, Tuner, Aux, etc. are all electronically identical. It is just a label to help you keep track of what you have plugged into an input. However an input labeled PHONO is completely different. It has the circuitry described above. A normal source plugged into that will be incredibly loud and bass heavy and could cost you your speakers. Conversely, plugging your turntable into one of the other inputs will be tinny and very low in level. You will feel like your stereo has been turned into a transistor radio (remember those?)
There are many different approaches to turntable design. We don’t want to bore those who are not into vinyl with too many descriptions of designs but will emphasize the major goals of a good turntable. The signal on a record is incredibly small. The table and tonearm must be very stable in order to pick up the low level detail an lp can provide. Resonance needs to be controlled, both in the arm and turntable so that the sound is uncolored. Speed stability is extremely important, as is the absence of noise from the motor assembly. Belt drive turntables have long been highly regarded because they decouple the motor from the table via a compliant belt. In recent times, with newer technology, direct drive table are starting to garner interest again. Their speed stability is usually excellent although the technology required to keep noise low tends to move them out of the entry level price points.
The last component in a vinyl playback source is the cartridge. Cartridges can cost as little as $25.00 or go well over $10,000.00. They are incredibly delicate devices to make and some are handmade and considered a cross between art and science.
There are two major categories of cartridges; moving magnet and moving coil. Both consist of a stylus, most commonly made of diamond, attached to a rod called the cantilever. The cantilever extends up into the cartridge body and is held in place by a compliant suspension. In a moving magnet cartridge, there is a magnet attached to the cantilever which is surrounded by magnets in the cartridge body. Movement of the stylus causes the coil to move relative to the magnetic flux of the magnets. This generates voltage and is what is sent to your phono stage. In a moving coil cartridge the situation is reversed. The coil is wound onto the cantilever and is surround by magnets. The coil moving within the magnetic field creates the voltage.
In general, moving magnets are found at the lower price points and have higher output than moving coils. Many moving magnets have replaceable stylus assemblies. Moving coils generally have to be retipped, sometimes for a significant percentage of the cost of the cartridge. Moving coils have lower mass and, as a result, can be “quicker” sounding, better reacting to musical transients. They typically have more finesse and better represent the spaciousness of a recording. Moving magnets can have powerful bass and some prefer them for rock and bass heavy material.
There are a several considerations when choosing the components of your analog playback system. The arm and cartridge need to be compatible with one another. This concerns the mass and compliance of each. Without getting too technical, some cartridges perform better on some arms than others. A good dealer will be able to direct you to a combination that mates well and is in keeping with your subjective preferences. The other issue is matching the cartridge with your phono stage. Obviously if you are using a low output moving coil cartridge your phono stage needs to be compatible with it. Some very basic phono stages will only accommodate moving magnet cartridges. Some give you a choice of MM or MC cartridges. More sophisticated ones allow you to choose both the amount of gain to match your choice of cartridge, typically one for MM and a couple of choice for MC, as well as adjusting the loading for either type. Again, virtually all MM cartridges use the same loading and some MC’s, particularly high output ones, use the same loading. There are normally several choices of resistive loading for MC’s. Some cartridges are more sensitive to these differences than others but, in general, lower resistive loading makes the bass warmer and the highs softer, higher settings the reverse. Manufacturers normally provide recommendations for these settings, with the final value determined by listening in the context of your system.
The last element of vinyl playback involves care and maintenance of your records and stylus. We recommend a liquid stylus cleaner which comes in a bottle with a soft brush attached. Carefully brush the stylus, moving it towards you and avoiding getting the liquid into the cartridge body. Follow up with a flat, round stiff brush and gently brush towards you again. This combination removes both lint and debris that can harden on the stylus.
Every turntable should have a carbon fiber record brush to be used before every playing. This removes dust and loose particles from the record surface. We also strongly recommend liquid cleaning of records as well, especially if you have or purchase old ones. This type of cleaning involves using a special cleaning fluid and a dedicated brush. The best way to accomplish this is with a dedicated vacuum based machine that spins the record while you apply the cleaning liquid and hold the brush against the surface for several revolutions. Then you swing a vacuum bar over, turn on the vacuum and, rather than simply emulsify and move around the contaminants, it actually pulls them off the record surface. There are varying degrees of effectiveness, automation, and cost for these devices. If you have an extensive record collection, it’s money well spent. Some new records sound better after cleaning as well.
Hopefully this will give a good feeling for the issues involved to continue or get back into the enjoyment of vinyl and analog music reproduction. While digital has made great strides in musicality in recent years, many people have retained their vinyl collections. It is also being “discovered” again by many, both new enthusiasts and those coming back to the format.