Final Project - Audio Amplifier Improvement
- akn0004
- Apr 29, 2016
- 2 min read
Our final project was the audio amplifier improvement where the desired outcome was to increase the output of the radio. Ali and I initially chose to add a Balun as our project but after we tested our simple radio and the output was so weak, we both agreed that it would be more exciting to improve the audio amplifier since it was an obvious problem.
When Ali and I were first tinkering with our simple AM radio, he was in charge of adjusting the antenna while I was in charge of adjusting the trimming capacitor, which was placed in parallel with the antenna and used to tune the antenna. We were both adjusting when I thought I heard a voice coming out of the speaker but due to the noise and the fact that it was so quiet, it was hard to determine that it was in fact the radio playing through the speaker. We determined that it would be best to try our radio outside of Broun, this eliminated most of the noise but there was still an issue with the volume. Below is a video of our simple AM radio.
Video 1: Simple AM Radio
After some research, we decided to improve our LM386 audio amplifier using the circuit in Figure 1.

Figure 1: LM386 Audio Amplifier Improvement
First, we added two 10 kOhm potentiometers, one to boost volume and the other to control the gain. The potentiometers that we used are shown in Figure 2. The potentiometer works by allowing current to flow from the input through the resistive element and into the output. The farther the knob is turned clockwise, the longer the current has to travel through the resistive material and this causes a decrease in gain. The farther knob is turned counter-clockwise, the less the current has to travel through the resistive material and this causes an increase in gain. Decoupling capacitors were also added to reduce some of the noise. Resistors and capacitors were added to reduce any voltage oscillation. Video 2 shows how the potentiometer works.

Figure 2: Potentiometers
Video 2: Potentiometer Demonstration
Finally, video 3 shows our final project demonstration. You can hear an obvious increase in the volume from video 1.
Video 3: Final Project Demonstration
In conclusion, two potentiometers were added to boost the volume and control gain. Capacitors and resistors were also added to reduce voltage oscillation which helped make the output remain smooth. Ali and I were very pleased with the outcome of our project. We were able to successfully improve the output of our audio amplifier.
Overall, this lab was a great experience. It was very neat to build a radio from scratch and learn how each component works. I enjoyed how each week it built on from the previous week. It was also rewarding that I did not have to rebuild the circuit from the previous week but instead add to it. I also gained experience in debugging circuits which will help me in the future.
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