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NAMM Sneak Peek

Rectifier

An electronic circuit or component designed to convert AC waveforms into DC. Normally these are used in the power supply of all types of equipment to provide the DC power source required by most electronic components for operation. Any electrical equipment that audio signals pass through possesses a rectifier as part of its power supply. In a sense, what a rectifier does is act as a one way gate where sinusoidal (see sine wave) current (AC) is changed to something closer to constant current (DC). Two types of rectifiers are half-wave and full-wave rectifiers, and are so named because of what they do with the negative portion of the wave. A half-wave rectifier literally lops off the negative portion and only sends along the positive part of the wave. This is basically what a single diode does. A full-wave rectifier takes the negative portion and “folds” it into the positive half, creating something closer to true constant current. Today all modern (including vacuum tube-based) audio equipment uses full-wave rectifiers; they are often a set of diodes in a special configuration located immediately after a power transformer. More modern designs have a single component that acts as a rectifier. Some tube amplifiers still have a tube rectifier as well. Although a rectifier doesn’t directly affect the tone or audio quality of a signal, it can still affect the sustain in the case of a tube rectifier because a tube will ‘sag’ in power output slightly when a power draw occurs (like when you hit a power chord on a guitar or play the amp at a loud volume). As the tube rectifier ‘catches up’ (so to speak), it will actually slowly reattenuate to its normal power output, which – believe it or not – can elongate the sustain of the note(s) being played.

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