◆A/D: Analog/Digital; an integrated circuit device that converts analog signals to digital signals. 　　　　◆Bandwidth: A range of frequencies defined by its highest and lowest limits. The audio bandwidth of human hearing has traditionally been defined as 20Hz to 20kHz.In pure electronic terms, the width of a communication channel, measured as frequency (in cycles per second,or hertz). A channels bandwidth is a major factor in determining how much information it can carry. 　　　　◆Dynamics: The level changes present in music. 　　　　◆Equalization: A correction made on playback of tape recordings to restore correct linear frequency. 　　　　◆Balance Feedback: Acoustic or ructure-borne vibrations that interfere with the operation of audio equipment. For example loud deep bass emanating from a loudspeaker may upset the performance of a turntable such that the pickup stylus reads the interference as bass signal. In extreme instances a loop of sound may be created resulting in high frequency instability; the more usual effect is a loss of clarity to the music signal. Bass becomes woolly and the rest of the signal unfocused. See also Negative Feedback. 　　　　◆Frequency response: The measured accuracy within db limits of a piece of audio equipment. For instance, hi-fi loudspeaker manufacturers specify the tolerance limits (usually +/-3dB) of each model alongside the operating frequency range (typically 50Hz - 20kHz). 　　　　◆Gain: An objective measure of voltage amplification. 　　　　◆Hi-Fi: Abbreviation of High Fidelity. Literally means honesty or truthfulness. In audio terms the context is accuracy to the original recorded signal, or more broadly authenticity to the composed music. 　　　　◆Pre-amplifier: The control amplifier featuring source switching, volume and signal processing circuitry. 　　　　◆Signal to noise ratio: Abbr: S/N ratio, measured in dB, it is an indication of the level of unwanted background noise generated by a hi-fi component (eg a tuner or amplifier). Again, the higher the number the better.