Monday, December 22, 2014

8W Stereo Amplifier

Good morning and welcome back! This post is about a 8W stereo, 4W each channel amplifier that can be conveniently powered from a computer power supply unit or a simple 12V-15V 1.5A transformer.


Where to use?


1. With a desktop computer as a cheap speaker, you can just hook up the speaker directly with your computer power supply unit saving you the cost for making a power supply unit.

2. Where bass is not much of a concern.

3. Can be used with Sealed lead acid battery or lithium battery so portable. 


What's good about it?


1. Requires only a few component.

2. Can be operated with a wide voltage range of 5V-20V, although at 5V it will only produce about 1W which is not practical but at 12V it produces around 4W on 4ohm load so I think that's the sweet spot.

3. Circuit is pretty easy to design.


 Components needed ( For mono build, for stereo you will need twice of these )

 1. Capacitor: 0.22uF ceramic  *2
                       1000uF 25V electrolytic
                       2200uF 25V electrolytic
                       10uF 50V electrolytic
                        470uF 25V electrolytic

2. Resistor:  1ohm, 4.7ohm, 470ohm

3. Integrated Circuit : LM383 


4. Adequate Heat sink.


The Diagram


You just have to make two of these to get stereo. 

you can add a 50Kohm variable resistor at the input for controlling volume.

You might omit the 1000uF capacitor with the power rail if your power supply has it's own.

If you don't want much lower frequency output you can use a 1000uF capacitor instead of a 2200uF.

Don't skip the 1ohm resistor and 0.22uF capacitor in series with the output, these are used for making the circuit stable and suppress oscillation, solder them as close as possible to the pin 3 and 4.

Higher supply voltage will yield higher output power but don't cross 20V.

You can control the gain of this circuit by changing the values of 4.7 ohm and 470ohm resistor.
But don't just add two variable resistor as they might short out the output.


Loud speaker with lower impedance will yield higher output power and higher impedance will yield lower output power so it is better to be on the middle, 4ohm will be enough.

You can easily make a two channel speaker system with this for general purpose use.

Make sure to follow the datasheet for proper grounding of the circuit.

Other resource:

How to use a computer power supply for general purpose.
Making an AC to DC circuit.
LM383 Datasheet.
Index to my blog.

Good luck and happy Experimenting.

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