Visual Sound, Inc. FP-PA18 18 W Audio Power Amplifier with Power Supply FP-PA18

RDL, Radio Design Labs The FP-PA18 is a high efficiency 18 W power amplifier with a line input, 8 ohm output, integral audio compressor and an automatic sleep mode. The FP-PA18 features a balanced line level input that may be connected unbalanced. A gain control located next to the terminal block is designed to be adjusted manually or with a trimming screwdriver. The gain range will accommodate standard unbalanced levels as well as professional balanced levels. The output drives one 8 ohm speaker or multiple speakers connected to present an 8 ohm load to the amplifier. The FP-PA18 includes an analog compressor/limiter for fidelity audibly superior to conventional class D amplifiers with digital limiting. The input GAIN setting determines whether the limiter alone is used for clipping suppression, or if the full compressor/limiter will be used to substantially increase the average output power beyond that of a standard 18 W amplifier. A red COMPRESSION LED flashes when the limiter is preventing output clipping. Normal audio level signals remain unaffected by the compressor thereby preserving audio dynamics. If the input level is increased so that the compressor is active, the LED remains dimly lit between peak flashes. The audio is compressed according to three dynamic time constants providing aural transparency while maintaining clean, unclipped amplified audio for input overloads of up to 20 dB. The FP-PA18, with compression, is capable of producing average audio output levels and clarity normally expected from amplifiers with a much higher output power rating. The FP-PA18 circuits are all designed for low power consumption. In the absence of an audio input, a digital timer is enabled to switch the class D output stage off. When this sleep mode is active, the amplifier module and its included RDL power supply consume less than 1 W of mains power. A control on the end plate sets the sleep mode delay timer to 5, 15 or 25 minutes. The control also permits the installer to bypass the sleep mode to conform to system specifications that require the amplifier to be active at all times. Upon detection of an input signal, the amplifier is nearly inaudibly and instantly restored to full operation within 150 milliseconds. The output stage includes an audio detector that illuminates the green OUTPUT ACTIVE LED and provides an active open collector output when amplified audio is present at the module output. This output is useful to control other equipment or