looking to build a small amp

[davidbball13]

ok so i was at my friends house the other day and saw an old computer case and i ripped out the computer speaker. and i connected it to a headphone wire into my ipod. it really is not that loud. i was looking at some schematics and most of them arnt what i am looking for. all i want is to use a 9 volt battery to power it and i was thinking that i could use a 100 hm: or higher Pot to control the volume. if the parts could be easy to find that would be great.

 

[Hero999]

Use an LM386 or two of them if you want stereo.

A 100k pot can be added to control the volume.

The circuit is on the datasheet for the LM386 and can be found using Google.

 

[stevez]

I think lots of people have already done this. It doesn't seem like a difficult project though your requirements, whatever they are, may limit your choices. I googled on "ipod audio amplifier schematic" and found quite a bit of stuff - some that might get close to what you need. Tell us what's wrong with what you find - as a way of helping describe what would suit your needs. Keep in mind that a 9 volt battery is only going to last so long - and louder means less battery life.

 

[davidbball13]

i did a search for "ipod audio amplifier schematic" and most of them were for headphone amps.all i want it is a mono amp. i will keep looking

 

[davidbball13]

how about this one
https://www.electro-tech-online.com/custompdfs/2008/03/CrackerboxAmp_Schem.pdf
the schematic is very hard to read but i will keep trying i am going to the shack tonight to get the LM 386
the part that i dont under stand the most is it says "in" and "out" what id that the positive or negitive wire from the head phone wires.

 

[audioguru]

You found a very stupid circuit.
1) Its input capacitor has such a low value that you won't hear any bass like a telephone.
2) the volume control of an amplifier belongs at its input, not its output.

The circuit is a mutilated copy of the one in the datasheet for the LM386.
It is a little power amplifier. It takes an input from an MP3 player or a CD player and amplifies its current enough to drive a little speaker or low impedance headphones.

 

[davidbball13]

ok so i got the LM 386 and tryed this circuit
http://www.josepino.com/circuits/index.php?mini_amplifier_lm386.jpc

that last one on the page

and i am confused on the input part
i did some of it and i get sound of my music but it is very distorted and not very loud.

please help

 

[davidbball13]

i have my negitive headphone wire comming off my ipod going into pin two for some reason i think it is wrong also i have a negitive off my pwoer supply in pin two also. aqnd the positive off the headphone jack in pin three.

please help

 

[Hero999]

Which circuit did you build?

Connecting a 100nF capacitor in series with an 8hm: resistor from pin 5 to 0V might help for a start.

You could also try the TDA7052 which is much louder.

 

[audioguru]

The circuit you found is missing important parts.
You connected your ipod directly to the input of the amp without the volume control and without the input coupling capacitor.

I show the circuit you found and beside it I show the circuit from the manufacturer's datasheet to show the missing parts.

What is your battery voltage?

 

[Hero999]

Why can't some people draw circuits correctly?

It annoys me when I see schematics for amplifiers that consist or square boxes and don't show all the pin numbers.

Always use the proper symbols and show the pin numbers.

 

[davidbball13]

my battery voltage is 9 volts
i am trying to do the one you guys sent me but i am new at looking at ICs that are shaped like triangles.
and again on the input i am confused on what input is is it the postive or negitive from the ipod

 

[Hero999]

The output from the iPod is an AC soundwave so positive and negative doesn't make any sense.

There will be three wires:

0V - probably be unsheathed.
Left - normally red.
Right - nromally blue.

For stereo you need to build two of these circuits.

You connect the 0V wire to the battery's negative terminal and the left and right connections to the circuits that are powering the respective speaker.

 

[davidbball13]

ok i built it but it can get really loud but when it gets loud it gets really distorted

any thoughts

 

[davidbball13]

ok makes a buzzing noise on the bass notes

 

[davidbball13]

i did not use my ipod headphones i use these crappy ones and i cut the wires i dont need i have black and red + and - i am assuming

 

[davidbball13]

also like a said before i dont want stereo all i want is mono

 

[Hero999]

Use a couple of resistors to connect both of the channels to the amplifier's input.

 

[audioguru]

With a new 9V alkaline battery and an 8 ohm speaker, the max output power of the little LM386 is only 0.45W which is not much. If you turn up the volume then the amplifier produces severe distortion because it can't make more than 0.45W. The max output power just before it distorts will be reduced as the battery voltage runs down. It is only 0.2W when the battery voltage is 6V.

An amplifier with a power output of 4.5W will sound twice as loud as an amplifier with a power output of 0.45W. If its volume is turned up too high then it will also produce severe distortion.

 

[mojoman0]

You may want to try different capacitor values on the output. You can create a high pass filter which will block the bass notes from being heard. This may eliminate them completely if you choose the wrong capacitance, but it may be better than a distorted muff.