Introduction: The Tiny Audio Amplifier
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.
Step 1: 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...
Step 2: Parts You're Gonna Need
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
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
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
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