Visual Sound, Inc. FP-PA18H 18 W Audio Power Amplifier with Power Supply FP-PA18H

RDL, Radio Design Labs The FP-PA18H is a high efficiency 18 W power amplifier with a line input, 8 ohm output and audio compressor capable of operation in a high ambient temperature environment. The thermal characteristics of the module case and construction throughout using high temperature components permit operation over a range of 0 to 70 degrees C. The FP-PA18H is ideally suited to outdoor applications, signage and other installations where ambient temperatures may become elevated due to limited convection. The FP-PA18H 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-PA18H 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-PA18H, with compression, is capable of producing average audio output levels and clarity normally expected from amplifiers with a much higher output power rating. The output stage includes an audio detector that illuminates the green OUTPUT ACTIVE LED and provides an active open collector output when the output stage is active and amplified audio is present at the module output. This output is useful to control other equipment or to verify amplifier operation using high or low frequency lowlevel test tones. The detector triggers with only 30 mW of output power at 20 Hz or 5 mW of output power at 20 kHz. A blue POWER LED illuminates when the FP-PA18H is powered from its external 24 Vdc po