Tuesday, May 2, 2017

5 / 9 / 12 Volt DIY Guitar Amplifier Circuit - Powered by TEA2025B (stereo)

Very cheap and simple guitar amplifier using the TEA2025B. You can get $0.99 for 10 unit of the TEA2025B IC on eBay.com where i got mine. This is my prototype demonstration on breadboard and it turns out not bad. The output sound is pretty decent for a small sub-speaker.

The clarity of the sound is obviously better than the recommended LM386 IC that people use for a small guitar amp DIY that i've found in Google. Dual speaker in the video is just a demonstration and it is possible to make a mono output using a different setup of the circuit schematic. For the time being i will stick to this until further improvement in the future. I would like to make this for real for myself so that i can fine tune the distortion and tone control. 

There will be improvement in the future for this circuit possibly with the addition of pre-amp circuit to allow controlling the tone and also alter the sound clarity.

TEA2025B IC How it works?

The IC internal structure actually build based on 2 separate amplifiers circuit combined and that's why it can generate stereo output sound. Refer to the diagram below as you can see pin 9 to 15 is the first amplifier with input, ground, and output. Pin 2 to 7 is the second amplifier circuit. If you observe closely over and over again the circuitry in the IC actually very simple.

Pin 16 is positive power source comes in.

The stereo version of the circuit optimize both input on pin 10 (first amplifier) and 7 (second amplifier) and the output separately out on pin 15 and 2 respectively. The component required is pretty simple and common.

2 x 0.22uF Ceramic capacitor
2 x 0.15uF Ceramic capacitors
2 x 470uF Electrolyte capacitors
2 x 10k potentiometer / variable resistors at the input
6 x 100uF electrolyte capacitors
2 x speakers

The internal structure of the TEA202B is as shown below.

The mono version of the amplifier only utilize the first amplifier input on pin 10. While the second amplifier input is connected to the ground. The component in the TEA2025B mono amplifier are as follow:

0.22uF Ceramic capacitor
2 x 0.15uF Ceramic capacitors
10kOhm resistor - reduce noise
6 x 100uF electrolyte capacitors

The advantage of TEA2025B is the power it uses is very small from 5 volt up to 15 volt as per datasheet. Even at 5 Volt the circuit is already sound quite loud and that gives the advantage of instead using batteries that will drain out juice we can use 5 Volt USB power from computers and mobile chargers.

TEA2025B Noise

Just like the LM386 the TEA2025B is very sensitive to ground noise - and there are all sort of noise coming from the surrounding environment including from strong RF frequency and floors. You can test this just put your hand closer to the circuit the noise becoming worst.

Secondly if you are using USB power supply there is also noise coming from the AC to DC conversion. That small electro-magnetic fields disturbance could really affect the amplifier sound.

How to handle the noise is to use a resistor - this you can experiment for example you can try 370 Ohm at the input signal connect to the ground. Secondly a resistor with the same value connect between the negative power source to the ground pin of the IC. This will reduce noise significantly and if you want it to be perfect you have to experiment on your circuit which one resistor value suit the best.

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