Vermes
Advanced Member level 4
This is a construction of stereo car amplifier on TDA 1562Q (H class). In addition to the TDA application, the device is equipped with a powerful preamplifier, drive indicator and auxiliary systems.
Preamplifier:
The preamplifier allows you to plug two sources (front line in and rear). The input is symmetrical, without ground connected to the minus of power. This provides lack of interferences during connection of the powered device to the car installation like CD ROM as a player, or a discman powered from the car lighter socket. Such actions cause large problem with voltage drops on the ground. This simple system eliminates the problem totally.
The preamplifier has adjustable sound tone for bass and treble. It begins to operate on the edges of the band, in contrast to many factory solutions. That gives a subtle and clear bass or treble boost. At the extreme setting of potentiometers, boost is significant. Additionally, the preamplifier is equipped with switchable Loudless system. There is also ATT function, which turns down the signal, for example during a call. Operational amplifiers used in this device: 741 and TL082. The system operates in configuration with artificial ground. PR 470K ballances channel gain and it can be set only once, during the run.
Power amplifier:
It is a classic application. Values of capacitors of load pump were increased in order to gain a better band. DIAG output was used. That output indicates overload by lighting red LED.
Dynamic indicator:
This function operates with simple transistor amplifier with automatics. That is why the indications do not exceed the end of scale and hands move nicely even at small levels of volume. Bulbs visible on the schematic backlight the indicator.
Auxiliary systems:
Auxiliary systems consist of supply with a filter at the input, several coils on a ferrite core, choke of ATX power supply (secondary side). There is also a switch with a relay. When you turn on the amplifier, you can also turn on another cooperating device.
Cooling control – at higher powers, rectified by the LED output voltage of the power amplifier charges the capacitor and supplies (through the emitter follower) the fan placed in the rear of the housing. That prevents from overheating the amplifier.
Pictures:
Link to original thread - Wzmacniacz samochodowy 2x55W z przedwzmacniaczem
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