How much "inrush current" will my amp draw during turn on?

Design features of the amplifier, including power supply design and transformer size, partially determine maximum peak inrush current for a given amplifier. In addition, the external factors of AC mains voltage and impedance vary greatly making exact values difficult to determine.

Many Crown amplifiers include "Soft Start," a feature designed to limit inrush current. Worst-case peaks for amplifiers without Soft Start may reach as high as 150 amperes; however, such numbers seldom have bearing on practical operation. For example, it is not unusual to find 3 or 4 Crown Micro-Tech amplifiers on a single 15A or 20A branch circuit without tripping breakers at turn-on. There are a couple of reasons why this is possible. First, peak inrush current is usually of such short duration that the breaker will not trip (maximum duration is approximately 18 msec). Second, Crown amplifiers are designed with design tolerances in the power supply start-up circuitry to make it highly unlikely for more than one amplifier channel to come out of standby during the same 18 msec interval.

If nuisance circuit breaker tripping is a concern, "motor-start" circuit breakers, which are designed to withstand the large inrush currents from electrical motors, may be used in place of standard circuit breakers. Contact a licensed electrician for more information about circuit breaker requirements and electrical codes in your area.