The new MA255 is a compact class D stereo amplifier with a 4 CH. stereo mixer built in. It has 20 watts per channel @ 4 Ohms. The class D low heat design gives the MA255 the ability to be mounted in very tight applications. It will work great in ceilings by projectors, or anywhere small and heat free amplification is required. The MA255 is built in an all metal chassis and weighs 1 pound. Overall dimension are 6.75" X 3.5" X 1.5". Bottom mounts are provided for permanent installations. The MA255 has an included 24 VDC external power supply. The 4 channel mixer section consists of 4 separate RCA stereo inputs, along with a 3.5mm (1/8") stereo input perfect for an ipod or laptop computer type input&amp.