Power Amp section of ARCAM AVR400 is uses a pair of power transistors numbered NJL3281 and NJL1302 with a symmetrical supply voltage of 52 VDC per channel.
AVR400 is a modern amplifier made by ARCAM that contains a multi-input circuit, both processing audio signals and even has a video signal processing feature for home karaoke and home theater purposes.
INFO
The Power Amplifier is produced in the 2010s and its a digital-based amplifier.
To find out the various features of this amplifier, please click the button below:
Video review about AVR400 on YouTube by AVLANDUK channel is HERE.
SCHEMATIC DIAGRAM
According to the service manual, this power amp contains 7 amplifier units that have a similar circuit.
However, in this article I’ll take one of the
schematic diagram for review.
The following is an edited and cropped schematic from the original one.
If we take a look at the circuit above, We will see that the power amplifier is requires many transistors to form a good and special amplifier circuit.
I can explain here, the amplifier consists of several sections, including:
- Firstly is Differential amplifier.
- Secondly is Bias current regulator.
- Voltage Amplifier Stages.
- Servo driver, with transistor Q5130 attached to a heatsink with the final power transistor.
- Over Current Protection. Its uses Darlington-connected Q5130 and Q5130 transistors.
- Amplifier Drivers. The transistors using are Q5150 and Q5160.
- Finally Power Amplifier. Its using power transistors Q5170 and Q5180 with numbers NJL3281 and NJL1302.
INFO
According to the service manual, the Supply Voltage of this PowerAmplifier is symetrical 52VDC. Its save until 58VDC.
Its means the power transistor will be able to producing until 243 Watts of power at a 4 Ohm load.
While the power transistor NJL3281 has able to make audio audio output until 200 Watts and its has 4 pins.
This transistor has an internal damper diode to prevent backflow from the speaker coil which is prone to damage the transistor. ( DATASHEETS NJL3281DG )