PM21 Dual Power Amplifier Module

65 Watt RMS into 8 Ohm.
Integrated Circuit.
Better than 0.01% distortion.
Over-current and over-temperature protection.
Differential (Balanced) or Single Ended Inputs.

The PM21 power amplifier uses a pair of National Semiconductor LM3886 Power Amplifier Integrated Circuits to implement two 65 Watt power amplifiers on a single circuit board. The pair can be used as a stereo power amplifier or the two amplifiers can be connected in a bridged mode to provide up to 150 Watt of power into a single load. For single ended operation the PM21 can drive 4 Ohm or higher loads. In the bridged mode the load should be 8 Ohm or higher. The PM21 has differential inputs that can be used as balanced inputs or as single ended inputs. The input can be either AC or DC coupled. This can be selected with a set of jumpers on the circuit board. With the jumpers installed, the coupling is DC and with the jumpers removed the coupling is AC with a cutoff frequency of 6 Hz. The gain of the amplifier is 40X (32 dB). Other gain factors can be realized by a change of resistors. This can be done by the user or at the factory. The power Integrated Circuits are mounted on an aluminum bracket. This bracket should be mounted on a heatsink supplied by the user. Several PM21 modules can be mounted on the same heatsink. The heatsink should have a total surface area of 100 square inches or more for each PM21 module installed. The circuit is electrically isolated from the heatsink bracket in order to make mounting easy. The available output power depends on the voltage and current rating of the power supply and the impedance of the load (8 Ohm or 4 Ohm). The power for the modules can be from a dual regulated power supply of up to +/- 35 VDC or from an unregulated source. The supply voltage should never exceed +/-40 Volt at any time. A simple unregulated supply can be assembled from a 48 Volt @ 1.5 Amp center-tap transformer, a bridge rectifier and two 10.000uF filter capacitors; This supply is good for 40WRMS into an 8 Ohm load. The assembly manual has a complete diagram of the amplifier. The amplifier modules are protected with an output safe operating area current limiter and a temperature sensor, all on the power IC's. The output current of the amplifiers will be limited to a safe value, so that they can not be damaged by short circuits at the output. In the event of overheating the amplifiers will turn off until they cool down again.

Frequency response: 10Hz - 50KHz +/- 1dB (AC coupled)
DC - 50KHz +/- 1dB (DC coupled)
THD at 1KHz: better than 0.01%;
Voltage gain: 32 dB (40x), non inverting or inverting;
Input impedance: 25 KOhm, AC or DC coupled.
Output load: 4 or 8 Ohm, DC coupled.
Max power output with 65 Watt RMS each channel, continuous, into 8 Ohm
+/- 35 Volt power supply
Max power output, bridged 150 Watt RMS, continuous, into 8 Ohm
mode,+/- 30 V power supply
Power supply voltage range: +/- 15 Volt to +/- 35 Volt
Dimensions: 5" X 3" X 1 "

Ordering Information:
PM21-A power amplifier

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