Definition of Engineering Phrases
"A"
"B",
"C",
"D",
"E",
"F",
"G",
"H",
"I",
"J",
"K",
"L",
"M",
"N",
"O",
"P",
"Q",
"R",
"S",
"T",
"U",
"V",
"W",
"X",
"Y",
"Z"
Loudness Control
Also called a Compensated Volume Control. An audio Loudness control combines both a Tone control and a volume control in the same circuit. The primary function of a loudness control is to boost the bass frequencies at low volumes , to compensate lower ear sensitivity at low volumes. Tone controls are found on lower-end audio gear because it saves front panel space on the unit and only requires one control knob, instead of two separate controls. Loudness controls may be found on any style audio receiver or amplifier. The editor has an old SA-8000X Technics receiver that has a Loudness switch. Technics is a brand of Panasonic.
Loudness Control
The potentiometer is or course the volume control, while the switches [which are coupled] provide the Loudness function. Both switches although shown to be separate are coupled so they both move with a single knob on the front panel of a receiver, as in a Double-Pole Double-Through [DPDT]. The DPDT is a common switch configuration. The top capacitor is switched into the circuit when the loudness switch is turned on, and the bottom capacitor is added to the circuit [shorted to ground when off].
The potentiometer has a fixed tap at the mid point of the range. An upgrade to the volume control would be to add a fixed resistor to either side of the potentiometer.
Related Audio Circuits;
Base Adjustment [low frequency control].
Treble Adjustment [high frequency control].
Midrange Adjustment Circuit [center frequency control]
Tone Control
Audio Crossover Networks.
Audio Amplifier Circuit.
A trimmer resistor is never used as a volume control. Potentiometers are designed for multiple adjustments, while trimmers are intended for less than frequent changes. Always use an adjustable resistor that is designed for the intended task.
