By Mark Frink • June 21, 2011 Be sure to take our PSW Photo Gallery Tour of the latest power amplifiers on the market Most modern power amplifier designs have abandoned traditional “linear” power transformer-based supplies in favor of digital switching supplies, shedding about half their weight in the process, getting into the range of 10 kilos or 22 pounds. Nearly all amps are two “rack spaces” high for a total of 3.5 inches in a standard 19-inch wide equipment rack, with depths ranging from roughly 10 to 20 inches. Various circuit designs have emerged over the years. Class AB designs provide low distortion at medium efficiency for high fidelity at moderate power levels and are still popular choices for compression drivers. However, AB uses a full-power DC supply at all levels, generating substantial heat at less than full output. Class D designs employ Pulse Width Modulation, using the input audio signal to switch the output devices at ultrasonic frequencies and then filter those frequencies with a low-pass filter. They’re very efficient, with a slight cost to frequency response, distortion and damping factor. Class G uses a second output stage that’s turned on when louder input signals require it, while Class H uses a single stage whose DC power supply is controlled by the input audio signal. Several other classes have been introduced by manufacturers that are proprietary modifications of Class D that address its shortcomings, combining high efficiency with high audio performance. Meaningful power comparisons are best made with both channels driven to reflect real-world situations. Four-ohm operation is preferred, though most modern designs provide stable operation with two-ohm loads as well. Subwoofer applications usually require many thousands of watts to drive today’s high-power 18- and 21-inch voicecoils. A rule of thumb is to match amps with at least twice the continuous power rating of the loudspeaker loads they’re driving. Read the rest of this post 1 2 About Mark Mark Frink Independent Sound Engineer Mark Frink is a touring sound engineer who has mixed monitors for numerous top artists. Comments Have something to say about this PSW content? Leave a comment! Cancel reply Scroll past the ”Post Comment” button below to view any existing comments. Your email address will not be published. Required fields are marked *Comment Name * Email * Website This site uses Akismet to reduce spam. Learn how your comment data is processed. Tagged with: Amplifier World Amplifiers Poll Real World Gear · all topics Subscribe to Live Sound International Subscribe to Live Sound International magazine. Stay up-to-date, get the latest pro audio news, products and resources each month with Live Sound.