READING THE WRITTEN SOUND

A phonograph cartridge is a micro-manufactured electro-mechanical device that tells your entire audio system what’s happening along the half-mile groove that’s cut into the typical analogue disc. The quality of the information provided by the cartridge is a critical determinant of how faithfully any audio system will reproduce the recorded sound.

CANTILEVERS & CARTRIDGE OPERATION

The cantilever (1) is a tube, or bar, with a diamond stylus tip (2) attached at one end, and a magnet (3) at the other (in the case of moving magnet cartridges). The cantilever must vibrate in exact sympathy with the rapid movements of the tip as it traces the audio signal, thereby moving the magnet attached at the other end.

Inside the cartridge body, magnetic conductors, or pole pieces (4), surround the magnet. A coil (5) of pure copper wire wraps around the leg of each pole piece. As the magnet moves, its magnetic field is distributed between the conductors. Magnetic energy flows through the center of the copper coils and produces an electrical signal. This signal corresponds to the original motion of the tip, and is electrically transmitted to the amplifier through terminal pins (6) bonded to the ends of the coils. The amplifier, in turn, drives the speakers.

Because the cantilever is located at such a critical juncture in the signal chain, it has a dramatic effect on the quality of sound reproduction.

MASS

The lower the mass of the cantilever the better able it is to accurately duplicate the sound pattern written on the walls of the record groove. The lower the combined mass of the tip and cantilever (the stylus assembly), the less the chance that the tip will lose contact with the groove, and consequently, with the signal. The greater the stylus mass, the more likely it is that inertia will cause it to skip over signal information as it oscillates rapidly, tracing the signal pattern while the groove walls speed past. This is particularly critical in the high-frequency range, where audio modulations are the smallest and most concentrated, and stylus tip movement is consequently the most rapid.

TRACKING AND TRACKABILITY

Tracking is the term used to describe the positioning of the stylus tip in the spinning record groove. Tracking effectiveness is referred to as tracking ability, or trackability. The quantitative measure of trackability was first developed by Shure. It is defined as the maximum velocity at which the stylus tip can move back and forth tracing the audio signal before it starts to skip. This measurement is expressed in terms of centimeters per second. It should be observed at several different frequency levels, while tracking force is held constant.

A tracking failure is referred to as mistracking. Serious mistracking, when the high mass of the stylus causes it to veer out of control, can permanently damage a record by altering the signal patterns in the record groove. Such damage can occur in just one play.

STYLUS TIP

The stylus tip traces the musical signal inscribed in the record groove, which can contain modulations as small as a millionth of an inch. Tip geometry is a critical factor in determining the accuracy of sound reproduction. The narrower the side, or contact radius, of a biradial diamond tip, the more precise its ability to trace the audio signal. This is particularly critical in the complex, densely packed high-frequency range. The better a tip traces the audio signal, the more accurate the sound reproduction, and the more consistent this reproduction is across the audible spectrum. The term "detail" is often used when referring to the accuracy of signal tracing, as in "high detail," or "lacks detail."

FREQUENCY RESPONSE

The consistency of sound reproduction across the audible spectrum is generally described by the term frequency response, which is the range over which the cartridge sound output is essentially level, or "flat" - with fluctuations neither above nor below a reference level on a monitor. Because every manufacturer has its own definition of what the term "flat" means, with some dropping this qualifier altogether, the comparative value of posted frequency response ranges across brands is limited.

TRACKING FORCE

Tracking force refers to the total force holding the stylus in place in the record groove. Effective tip pressure on the record can actually be as high as several tons, due to the extremely small contact area between diamond tip and groove surface. The amount of tracking force is the major determinant of normal record wear (as distinguished from record damage, which is typically caused by mistracking.) The lower the tracking force, the lower the record wear, but also the lower the trackability. The best cartridges, such as Shure’s V15VxMR, are able to achieve high trackability at a low tracking force.


What is a Dynamic Microphone?
A dynamic microphone operates like a speaker "in reverse." Changing sound pressure moves a diaphragm. This moves the coil, which causes current to flow. But, instead of putting electrical energy into the coil (as in a speaker) you get energy out of it. Dynamic microphones are renowned for their ruggedness and reliability. They need no batteries or external power supplies. They are capable of smooth, extended response, or are available with "tailored" response for special applications. Output level is high enough to work directly into most microphone inputs with an excellent signal-to-noise ratio. They need little or no regular maintenance, and with reasonable care will maintain their performance for many years.

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What is a Condenser Microphone?
Condenser (or capacitor) microphones use a lightweight membrane and a fixed plate that act as opposite sides of a capacitor. Sound pressure against this thin polymer film causes it to move. This movement changes the capacitance of the circuit, creating a changing electrical output. In many respects a condenser microphone functions in the same manner as an electrostatic tweeter, although on a much smaller scale and "in reverse." Condenser microphones are preferred for their very uniform frequency response and ability to respond with clarity to transient sounds. The low mass of the membrane diaphragm permits extended high-frequency response, while the nature of the design also ensures outstanding low-frequency pickup. The resulting sound is natural, clean and clear, with excellent transparency and detail. Condenser elements have two other design advantages that make them the ideal (or the only) choice for many applications: they weigh much less than dynamic elements, and they can be much smaller. These characteristics make them the logical choice for line - or "shotgun" - microphones, lavaliers and miniature microphones of all types.

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Microphone Techniques for Music/Sound Reinforcement
Recommended microphone type and placement for a large variety of vocal and instrument situations. Open It

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Microphone Techniques for Music -- Studio Recording
In this guide, Shure Application Engineers describe particular microphone techniques and placement: techniques to pick up a natural tonal balance, techniques to help reject unwanted sounds, and even techniques to create special effects. Open It

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Selection and Operation of Wireless Microphone Systems
This comprehensive booklet provides the reader with a more in-depth understanding and knowledge of wireless systems and their operation. Open It

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User Guides and Specification Sheets

• Personal Ear Monitor Systems
• Wired Microphones
• Wireless Systems

• Impedance - Output impedance is a measurement of the AC resistance looking back into the microphone. Generally, microphones can be divided into low (50-1,000 ohms), medium (5,000-15,000 ohms) and high (20,000+ ohms) impedance. There is a limit to how much cable should be used between a high-impedance microphone and its input. More than about 20 feet will result in a loss of highs, and loss of output level. But by using low-impedance microphones and cable, microphone cables can be almost any practical length, with no serious losses of any kind.
  
  
• Balanced Output - A balanced output offers real advantages to the serious recordist. Balanced lines are much less susceptible to RFI (Radio Frequency Interference) and the pickup of the other electrical noise and hum. In a balanced line, the shield of the cable is connected to ground, and the audio signal appears across the two inner wires which are not connected to ground.
  
  
• Microphone Phasing - Microphone phasing is most important when two (or more) microphones are to be used close together, then mixed into a single channel, or when recording in stereo. If they are wired out-of-phase to each other, signal levels and tonal balance will be adversely affected, and can change abruptly with small movements of the sound source or the microphones. In stereo there may be poor imaging, imprecise location of instruments and reduction of bass.
  
  
• Sensitivity - Sensitivity ratings for microphones may not be exactly comparable, since different manufacturers may use different rating systems. Typically, the microphone output (in a sound field of specified intensity) is stated in dB (decibels) compared to a reference level. Most reference levels are well above the output level of the microphone, so the resulting number (in dB) will be negative. Thus a microphone with a sensitivity rating of -55 dB will provide more signal to the input terminals than one rated at -60dB.