Most people building guitar amp based on the LM386 IC which is noise prone or the TDA2030 lack of sound. Although they are cheap they are not good enough to produce the best of a basic guitar amp. So we are going to use another IC called TEA2025B which is equally cheap but much louder and less noise.
Note that the TEA2025B is a dual amplifier IC combined into one - however, instead of utilizing its dual output we are making it into mono-output so that we don't have to use two speakers as the output sound. This makes the work easier and the sound still great.
The outcome of this project is good for acoustic guitar amplifier but it's also good for basic electric guitar.
Step 1: Understanding the TEA2025B IC
Look carefully at the IC structure Pin 10, 11, 12, 13, 14, 15 belongs to the first amplifier of the TEA2025B while Pin 7, 6, 5, 4, 3, 2 belongs to the second amplifier of the IC. Pin 16 is the positive (Vss) and Pin 1 Bridge.
You can choose to make double output (dual amp) using this single IC but in this project, we combine them to make a mono amp and it still sounds as loud.
Step 2: Schematic Diagrams & Components and Tools
We are going to need the following electronic components for the guitar amp project
- 2 x 470 uF Electrolyte Capacitors
- 2 x 0.15 uF ceramic capacitors
- 4 x 100 uF Electrolyte capacitors
- 1 x 0.22 uF ceramic capacitors
- 1 x 10 kOhm potentiometer + 1 knob
- 1 x 330 Ohm resistor
- 1 x sub-speaker (small speaker will do)
- 1 x 6.3 mm jack port connector for input from guitar
- 1 x USB port for power input
- 1 x through-hole PCB
- 1 x small project box
- Drills to make holes
- Solder iron
- Pliers to cut excess components pin
Refer to the pictures for the schematic circuit diagram
Step 3: Assembly
Cut the PCB size 100 mm Length x 60 mm Width
Since the project box size dimension is 100 mm x 60 mm x 25 mm we need to cut the PCB based on the 100 mm length and 60 mm width. To make it perfect fit measure the PCB against the box size to reduce mistakes and save time doing the unnecessary.
Solder the 16 pins IC socket onto the center of the PCB board
Once that is done you can start solder the TEA2025B at the center of the PCB - the position is important because many of the other components that need to connect to the main IC, later on, can be placed close to it. In this process, you can solder directly the IC onto the board or you can solder the 16 pins through-hole IC socket. The advantage of using the socket adapter is for convenient and easier to take out the IC if it is faulty and replace it with another without re-soldering. That saves a lot of time - in the process. Apart from that good IC can be removed and reused without damaging it with hot solder.
So in this project we soldering 16 pins IC socket to the board in the center position. Once that is done then slot in the TEA2025B IC onto the socket adapter.
Solder Pin 4, 5, 7, 9, 12, 13 to ground (negative USB port)
Why so many pins connected to the negative (ground) because of the IC consist of 2 amplifier circuit in one. Pin 4 and 5 negative belong to the first amplifier while 12 and 13 belong to the second amplifier. Pin no.9 is the ground for the sub. In this project, I do this combination of connection Pin 7 to 5, and Pin 4 connect 13 and Pin 5 connects to 12 and then 9 connect to 12 and 13 then connect the negative power source to the pin 9. So the negative flow is from 9 to 12, 13 and then pass to 4 and 5.
Solder Pin 16 TEA2025B
We are going to start with pin 16 - solder it to the positive of the USB port indicated as +Vs in the circuit diagram. Then solder 100 uF electrolyte capacitor positive to pin 16 and the negative to negative (ground) of the USB port. This capacitor is to stabilize the current flow to the circuit.
Solder Pin 14 and 15
Using 470 uF electrolyte capacitor solder its positive terminal to pin 14 and negative to the pin 15. Then solder pin 15 to the output RCA jack. Still, on pin 15 solder 0.15 uF ceramic capacitor to the negative (ground) of the USB port. The overall connection of this circuit is for the first output of the amplifier.
Solder Pin 2 and 3
Using 470 uF electrolyte capacitor solder its positive terminal to pin 3 and negative to pin 2. Then pin 2 solder to the other connection of the RCA jack output. Then take 0.15 uF ceramic capacitor and connect to the negative (ground) of the USB port. This will be the second output of the amplifier.
Now we have completed soldering all the output of the amplifier and we move on to the input side. Note that the function of the 470 uF and 0.15 uF capacitors again is to produce stable sound to the output speaker.
Solder Pin 10 input sound
Solder 0.22 uF ceramic capacitor and 330 Ohm resistor in parallel to the center of the 10 kOhm potentiometer. Solder the right pin of the potentiometer to the guitar in of the 6.3 mm jack connector port. Then the right pin of the potentiometer solder to the negative (ground) of the 6.3 mm jack connector port. The 0.22 uF cap and 330 Ohm resistors are a very effective combination to reduce the input noise. Without them, the noise would be unbearable and produce a loud echo.
Solder pin 11, 6, 1 feedbacks
Solder the 100 uF electrolyte capacitor positive terminal to the pin 11 and negative to ground (negative) of the USB port. This is the first amplifier feedback. Then solder another 100 uF electrolyte capacitor positive terminal to Pin 6 and negative terminal to Pin 1 Bridge. This is the second feedback of the amplifier.
Solder Pin 8
Solder another 100 uF electrolyte capacitor positive to pin 8 and the negative to negative (ground).
Now you are done soldering all the TEA2025B pins to all the necessary connections (components). Please note that it is very important to make the circuit as compact as possible - which means ensuring that all the components stay very close to the IC. This will make the sound very efficiently loud and less noise and of course quality capacitors and resistors component would also significantly add to the effectiveness of this amp. Except the speaker can be far from the circuit otherwise if it is too close it may generate a loud echo.
Apart from that instead of dead soldering all the components I use male pin connectors for each of the component. This allow me to connect them using female jumper dupont cable for testing. However this is optional and you can solder them directly is no problem just that if anything goes wrong you need to desolder them and resolder which could take too much time and may damage the board. Using a jumper cable connector allow flexible testing and ensure everything connect correctly and easy to fix if connection is wrong.
Step 4: Testing
In this project, I am using the jumper dupont cable so it's pretty easy to connect each of the components to one another. If it went wrong it's very easy to reconnect them - apart from that the IC socket saves a lot of time as well if the IC is damaged due to wrong connection or high current we can simply take it out from the socket and replace it with the new one. Anyway, the IC is very cheap and you could get 10 pieces for few bucks only.
Now connect each component - or if you have soldered them directly you may skip this part. Then get your guitar cable and plug onto the guitar and to the input jack of the amplifier. Get USB cable to connect it to power bank, computers, laptop or USB charger anything that generates 5 volts would work just fine.
If you listen to a crisp sound and able to adjust the volume using the potentiometer knob working that everything should be good. Note that this guitar amp is very basic and there is no variation to distortion, whammy, or whatever fancy effect. However, the sound very good and clear on acoustic - and for that, it should work well on electric guitar as well.
You don't need a fancy expensive speaker - a small sub-speaker would do good and I have compared the sound to most of the DIY guitar amp that people make on YouTube using TDA2030 or LM386 I think the TEA2025B doing better job in terms of noise reduction as well as the loudness of the sound. In fact, it could generate an echo when it is very loud.