65 Watt RMS into 8 Ohm.
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
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
Specifications:For free manuals download go here.
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 "
PM21-A power amplifier