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Picture of The tiny Audio Amplifier
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em386_height.jpg
A tiny, cheap Amplifier where it can be incorporated almost anywhere.
Connect your MP3,iPod,Laptop,Cell Phone... and you got your self a DIY portable stereo.
It can be powered using batteries and be helpful in many cases.
It is capable to drive a small 8 Ohm speaker or even a combination of a small in diameter
say 2-3 inch woofer and a tweeter for better acoustics.
 
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Step 1: The main ingredient

Picture of The main ingredient
The main ingredient is the LM386N IC witch is a low voltage audio power amplifier.  
Let me stay here and say that I'm not the Columbus, who discovered America!
There are plenty of information out there, just type LM386.
To begin with...
LM386.pdf264 KB

Step 2: Parts you're gonna need

Picture of Parts you're gonna need
LM386 UPPER VIEW .bmp
LM386 PCB LAYOUT.bmp
LM386 SPC.bmp
PARTS PIST – Amplifier – For stereo operation all parts (x2) except P1

A small PCB 3,5cm x 3,5cm
IC = LM386N (8 pin chip) & each case
R1 = 10 Kohm (Brown, black, orange, gold)
R2 = 10 Ohm (Brown, black, black, gold)
R3 = 620 Ohm (Blue, red, brown, gold)
P1 = 10 Kohm trimmer for PCB or logarithmic potentiometer to be screwed on a project box
          [for stereo operation ask for 1 (one) stereo logarithmic potentiometer]
C1 = 10uf/25V electrolytic capacitor (caution: +/- polarized item, follow the recommendation)  
C2 = 100uf/25V electrolytic capacitor (caution: +/- polarized item, follow the recommendation)
C3 = 220uf/25V electrolytic capacitor (caution: +/- polarized item, follow the recommendation)
C4 = .01uf/63V ceramic capacitor (non polarized)
C5 = .033uf/63V ceramic capacitor (non polarized)
C6 = .047uf63V ceramic capacitor (non polarized)
LED = 3mm red led (caution: +/- polarized item, follow the recommendation)
Connectors = 3 x double PCB connectors
POWER = 9V Battery & clip or build a 12VDC stabilized power supply to be connected to 110VAC or 220VAC mains,
depends on where you live.

Step 3: 12VDC Stabilized power supply

Picture of 12VDC Stabilized power supply
SPowerS.bmp
PARTS LIST – 12VDC Stabilized power supply

T1 = Transformer 220VAC mains/15VAC – 300mA
         (HAZARD WARNING: ~/~  at purchase ASK WHERE TO CANNECT THE 220VAC)
BR1 = bridge 1Ampere (caution: ~/~/ +/- polarized item, follow the recommendation)
U1 = LM7812 (caution: +/- polarized item, follow the recommendation)
R1 = 680 Ohm (Blue, gray, brown, gold)
C1 = 1000uf/25V (caution: +/- polarized item, follow the recommendation)
C2 = 100nf ceramic capacitor (non polarized)
C3 = 100nf ceramic capacitor (non polarized)
C4 = 10uf/25V (caution: +/- polarized item, follow the recommendation)
LED = 5mm red led (caution: +/- polarized item, follow the recommendation)
220VAC Mains wire.

Step 4: TOOLS you're gonna need

TOOLS you might need

Solder iron, not more than 25W
Solder wire for PCB soldering
Small Handheld drill
Drill bits of 0.8mm & 1mm
Plumbers Jel-flux copper cleaning paste. Helps the soldering process a lot.
Apply a small quantity of paste at the copper side of PCB, then place the components on and solder.
Small Nail cutter for cutting the components spare wire on PCB after the soldering is done.
Pure Acetone for cleaning the PCB after the soldering is done.
A few drops with the use of an old tooth brash will do the job just fine.

Step 5: OPERATION

Picture of OPERATION
Just to drop some ideas, there are many ways to power the amplifier.
It can be powered from a stabilized power supply, one use batteries, rechargeable batteries, AA or AAA or one 9V cell or (x2) 9V cell in parallel for longer play and many more, really it's up to you to decide.
The LM386 requires 4V – 12V to operate with typical operation at 9V.
more voltage = more acoustic power (milliwatts)
If you need a stereo amplifier (R channel + L channel) then tow (2) circuits must be constructed.

A few things you need to know...
The LM386 does all the jab with only a few external components.
Connecting C1 through [jumper SW] to IC pins 1 & 8  a GAIN of 200 is applied.
In practice you will notice an increased volume and also more distortion (not good).
The purpose of 200 GIAN can be useful in cases where the source  is to low for example a microphone pre-amplifier.
In most cases if input source is an MP3 player a typical GAIN of 20 will be enough for a decent output.
Adding R1 & C5 it's optional to the circuit and acts as a BASS BOOST filter, sounds better but drops the volume a bit.

Step 6: CONSTRUCTION

Print the PCB layout as is from the given picture  (72 dpi). A laser or ink jet printer can be used.
Depending on the process you will follow, turn the layout left or right.
There are many indestructible on how to print a PCB and how to etch.
Follow the illustrated components picture to place the parts.
Pay attention for the components polarity when stated  from the parts list.
The real life picture showing the amp  is from an earlier version and works great.
The illustrated one it is a bit larger but have enough room for the connectors.

I am open to any questions, comments and suggestions and hope this instructable was helpful
Have fun!
tbenard1 year ago
Can anyone tell the voltage rating required for each component.

safest bet is atleast 35v for the capacitors... as long as it is atleast 1-v higher than the supply voltage, you should be grand :)

stubbsonic1 year ago
Any idea how many watts this produces?
frapedia (author)  stubbsonic1 year ago

As most manufacturers claim, the LM386 can output at 6v input / 8 Ohm load(speaker) = about 300 mW. For 9v input / 8 Ohm = about 600 mW.
You can google around for < lm386 datasheet > and see the chart: device dissipation vs output power - 4Ω - 8Ω - 16Ω load.

bsaw1 year ago
Can you give me the audio jack image for stereo operation? or you can just give the Simulation? :D
frapedia (author)  bsaw1 year ago

google around for < stereo audio jack wiring >
Depending on your needs, for audio input the most common uses are 2 x RCA connectors or a female stereo 3.5mm jack.

frapedia (author) 2 years ago
I'm afraid i have lost some files with the actual pcb dimensions. The below dimensions given are for the Ver.:1, the first 3 pictures of the instructable.
For those who wish to use the Ver.:2, the illustrated ones here is a tip. Use a paint App like corel photo-paint. At the print process shrink the illustrated pcb image to the point the LM386 ic pins fit to the printed holes of the printed pcb. This is a try and error process and i know it's not the best way, i am sorry for that.
frapedia (author) 2 years ago
I have added 2 more pictures showing the PCB dimensions.
frapedia (author) 2 years ago
I'm sorry for the delay guys but it's summer time, you know...
Anyway, PCB width = 28.5mm x PCB height = 25.5mm form border to border.
If it is to use the Amp as audio/music instrument it's best to add the low filter (R1 + C2) to the circuit as it acts like a bass boost. Now, if for any reason you do not wish to use the low filter use a wire between PIN1 and PIN5 of LM386.
C1 capacitor (MAX GAIN) boosts the volume and again if you are intent to use the Amp as music instrument it's best to add the C1. If for any reason you do not wish to add C1 simply removed.
SW (switch) added to connect/disconnect the C1 and can be removed from the PCB.
Remember to connect a wire between C3's positive pin and LM386's pin 5.
frapedia (author)  frapedia2 years ago
P1 is a potentiometer, the usual knob all amplifiers have to adjust the volume.
Stensrud2 years ago
What are the dimensions for this amplifier?
cparker12 years ago
Can you add a picture diagram that shows all the parts together on the PCB like the one for the one that doesn't have bass boost so I can see what it looks like? Thank you.
mitsof2 years ago
I have made the pcb based on your schematic.Here is the whole process. http://www.youtube.com/watch?v=-XhLMPXxDQk
mitsof2 years ago
Φίλε τί διαστάσεις πρέπει να έχει το pcb;Η εικόνα που δίνεις είναι πολύ μεγάλη.Μπορείς να βάλεις μια εικόνα του pcb στις πραγματικές του διάστασεις;
rimar20002 years ago
This seems ideal for my needs. Would you think this is a suitable electronic project for a person like me, that barely can solder a cable? I am half enthusiastic, half fearful to initiate it.
frapedia (author) 2 years ago
salexandridis,
sorry for the delay!
nice to know you like it :)
[SW GAIN] is a jumper where C1's positive (+) is being connected to the rest of the circuit. Therefore a gain of 200 is applied.
Wraio kyklwmataki re Frapedia! Sta pin SW kai GAIN ti syndeeis? Diakopth me thn mia epafh sto SW kai thn allh sto GAIN?
Eyxaristw ek twn proterwn.


And for the rest of the world who might encounter simiral problems:

"What should be connected to pins SW and GAIN? Is it a switch of which one contact is connected to SW and the other to GAIN?"
xbuntu3 years ago
Shouldm't the PCB be 10 times larger each way
frapedia (author)  xbuntu3 years ago
Yes you're absolutely right, it has to be 3,5 cm x 3.5 cm. my mistake!