How do I choose the right amp?

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Fri Dec 19, 2008 4:32 pm

  • How do I choose the right amp?

    Usually there is no one “right” amplifier, but instead several that will do the job as needed. Among them, you may wish to consider features, weight, future uses, price, and other criteria to make your selection.

    First, choose your loudspeakers—for the sound quality and coverage you need—and then choose suitable amplification to drive them.

    A general rule of thumb for choosing a suitable amount of amp power is to match the amplifier’s power rating to the loudspeaker’s program power rating. It doesn’t have to be an exact match—within about ±20% is fine. For example, if you have two 8Ω loudspeakers with a program power rating of 350 watts, then you could look for a two-channel amp rated at around 280 to 420 watts per channel into 8 ohms (GX3, RMX1450, RMX1850HD, PLX1104, or PLX1802). An alternate approach, if you need only mono operation and will not need to add other loudspeakers, would be to choose an amp rated at about 560 to 840 watts into 4 ohms in bridged mono (RMX850).

    The idea is that if you choose your amp this way and avoid driving it into significant clipping, your loudspeaker will be fairly safe from blowing out due to overpowering.

    If the loudspeaker has no program power rating, then use about 1.5 to 2× its continuous (often called “RMS”) power rating as a target.

    You’ve probably noticed that QSC has many lines of power amps. If you buy your pro audio gear from dealers, music stores, or online retailers, you’ll find the general-purpose amps: GX, RMX, and PLX2. The GX are basic entry-level two-channel amps, good for loads of 4 ohms or higher per channel. The RMX amps are a line of two-channel amps that range from fairly low power (185 watts per channel into 8Ω) up to very high (2500 watts per channel into 2Ω). The PLX2 amplifiers employ the high-performance lightweight power supply technology developed for QSC’s renowned PowerLight touring amps.
    Bob Lee
    Technical Communications Developer
    QSC, LLC
    Fellow, Audio Engineering Society
    "If it sounds good, it is good." —Duke Ellington
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    Bob Lee
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