500W class AB amplifier with integrated source

I decided to design this amplifier since this circuit has great audio quality and impressive stability which makes this circuit perfect to work in concerts or professional sounds, this card was designed because I have observed that in concerts and events the amplifiers, this because they work at the maximum of their power making the components work stressed and in a very risky range, I designed this amplifier to work as relaxed as possible using components that work in a safe range, all this to give you a lot of reliability and minimize the possibility of failure in some important event.This amplifier can be powered by a range of very varied voltages that can go from 45V DC to 80V DC.

The power of this amplifier is 500W at 4 Ohms fed with a 53V-0-53V ac transformer, this amplifier has the advantage of including the source and the amplifier in a single card, which facilitates the installation, change and maintenance of where it is installed.

the source is composed of a 50 amp diode bridge and four powerful 10000uf at 100V capacitors that will withstand the current peaks and voltage drops that this amplifier can cause without problems.

the start-up of this amplifier is very simple, you just have to install all the components, connect the transformer to the board, connect the audio signal and the speaker, after this you need to make 3 small adjustments to improve the sound quality and the stability of it.

Offset: Adjust the DC of the output terminal, because it is necessary to make a circuit that can work in a ± 45 to ± 100V circuit, so there may be some small DC in the output terminal, so we use this potentiometer to correct this problem and the output as close to 0.00V as possible.


Gain: Adjusts the gain level, as we increase the source voltage, the amplifier must increase the gain to take advantage of the source energy that is sent to the speaker, while in an amplifier with low voltage but with a lot of gain it could saturate the signal turning into distortion. This potentiometer adjusts the correct gain level, preventing the amplifier from distorting at full power feeding it in the minimum range of supported voltage or sounding very low at the maximum supported voltage.(U6).

Bias: Adjusts the quiescent current according to the output setting. It should be adjusted until between Base and Emitter of the output transistors it measures between 575mV to 600mV.(U5).

Despite the fact that the efficiency of this amplifier must be around 65%, the use of two good heatsinks that can dissipate the heat that this amplifier can generate becomes mandatory.

All transistors must be rigorously adjusted with screws and nuts, insulating lenses and thermal paste to improve thermal transfer.

It only remains for me to remember that I recommend the use of top quality components for the assembly of this amplifier since the above will ensure the success of this great project, I recommend using a preamp and speakers of a power according to the amplifier.

This amplifier was designed on a 350mmx100mm double layer PCB to have higher stability and avoid interference.

I want to thank PCBWay for all the support given to my projects and for allowing me to share my experiences and projects with the whole community

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Nov 01,2020
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