Pocket transistor Amplifier

In this instructable I will show you how to make a simple amplifier that can be used for a variety of different things. Because the 8ohm speakers are very quiet, it wasn't worth connecting a 1/4 in. jack to it for my cello pickup or my dads guitar, so I decided to make ipod speakers with it. When I tried directly connecting the ipod to the speakers the signal was very weak, so I decided to connect it to a very simple transistor amplifier. 

Step 1 Materials

Materials:
-altoids tin
-small audio transformer (too big makes it sound fuzzy)
-0.1µf ceramic disk capacitor (104)
-2n3904 NPN transistor
-two 8ohm speakers
-battery case for one AAA batttery
-3.5 mm male audio jack
-wire
-SPST switch
-10k potentiometer 

Tools:
-pliers
-metal cutters
-drill
-soldering iron

Comments

[Begradoo]

I built this circuit by the schematic and your descriptions of how to connect it to the transformer.
I got no sound out of the speaker and my transistor nearly had a meltdown. I double checked all the connections and everything seemed correct.
Any ideas what I messed up?

[Higgs Boson]

Do you know how strong of a signal was coming from your audio in?

[Begradoo]

very low at first. 5% volume on my Ipod. then I slowly turned it up as I didn't hear anything, and as the 10K pot was at minimum.

[Higgs Boson]

Well I found that with my pot it took a bit of adjusting it and the ipod volume before I was able to hear nice loud clean sound. As for the transistor I suspect you mixed up the emitter and collector pins. try switching it around and see if it works, though make sure it isn't already broken first.

[Begradoo]

I'll take it back apart and rebuild from zero.
I also spoke with a buddy of mine who mentioned testing the leads on the transformer, as the one I am using IS a 5 pin, but not specifically an audio transformer.
I am sure I had the transistor pin out correct but I will double check before powering the next build.
Thanks for the help!

[Higgs Boson]

Your welcome. Let me know if you need any more help, and if you get it working. Good luck!

[lukeD]

is there a way to NOT use the transformer?

[Higgs Boson]

Not with transistor oscillators. It is a major disadvantage of using transistors as amplifiers. If you wanted to not use the transformer, you'd probably want to look at some stuff with opamps. 386 would probably work well.

[blinkyblinky]

I'm surprised. 1.5 volts...

Is this circuit yours?

[Higgs Boson]

Sort of. I saw the single transistor amp circuit in a book, but I played around with things like voltage, and values of the components to get it to work with the ipod. I found that 1.5 volts actually worked best.

[blinkyblinky]

Cool.