How to Make a Portable Mp3 Amp From Old Computer Speakers





Introduction: How to Make a Portable Mp3 Amp From Old Computer Speakers

have you got a pair of old computer speakers lying around that you dont need?
want to make a decent iPod/mp3 amp?
these speakers are powered via a PP3 9V battery

snap on clip for 9V batter
9V battery
audio source

soldering iron and solder
screw driver
wire cutters/teeth
wire stippers/teeth

Step 1: Disassemble Speakers

your speakers might not be 9V, if there not you could possibly use AA batteries in series in aholder or use a gel cell, bit heavy though.

disassemble the speaker with volume and power input, unscrew it from the back, there should be a transformer attached to the back, this is what takes the 230V (110V) down to 9V or the working voltage for your speakers.

on the transformer it should say the primary and secondary voltage, the secondary voltage should be lower, 9V hopefully, if it is not 9V you may still be in luck, if it is 3V use two AA batteries, if its 6V use 4, if its 12V use either 8 AA batteries or a car battery or gel cell battery, look online for one.

however, if you want, you can put a batter inside if you have room, or outside if you dont, and put the speaker cases back together.

Step 2: Removing Board, Speakers, and Wires

now you need to remove the board and speakers from the two speakers. to remove the speakers there should be screws holding the speaker in at the corners. for the board there is likely to be screws holding it into the case, and the potentiometers will probably have nuts holding them on. so pull the knob off the front of the volume control and the nut should be exposed. use needle nose pliers or similar to remove it, then repeat for any other control knobs.

Step 3: Adding Power Connector and Removing Second Speaker

in this step we will remove the speaker from the second speaker case, and also add the power connector.

for these speakers to be powered from a 9V battery or whatever battery is used you need to add the connector, if you are using a 9V battery, use a PP3 battery clip, you can either solder it directly onto the board or you can cut the wires from the transformer and add it there, this will give you more cable length, and mean you wont have to desolder and solder onto the board.

if going for the second method strip both wires (teeth or wire strippers) then add the connector and twist the wires together and apply some solder.

if you want you can test it now, plug the input jack into your audio source, mp3 player etc.
if you hear music, well done! if not, not so well done, check cables, and battery life.

if all goes well, time to remove the second speaker, unscrew the case and then unscrew the speaker from the casing. now you will have to either cut the cable from the speaker to the board or melt the solder off, thread it though the hole in the back of the case, then resolder, i went for the first option, but as the cable broke off the speaker later i ended up doing the later option but slower.

Step 4: Finishing Up

now you should have finished, all you have left to do if but the board and speakers in a suitable housing or put it back in the old housing, i was planning on mounting the speakers inside my bag with holes cut for sound to escape, but thats for another instrucable

hope it all works! have fun sharing your music tastes to the public!!!



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29 Discussions

I tried this. I got some $3 computer speakers. I tried to find the input info, they took a 7.5VAC wall adapter. I read the comments on here; I ended up seeing the rectifier set up on the circuit board. I took an exacto knife and cut the traces from the positive and negative outputs of the rectifier then I soldered in a connection for positive and ground. I hooked it up to my variable DC power supply and supplied it with 7.5VDC 300mA (or whatever it wanted for its load) , I put on a YouTube video and hooked up the speakers via an aux cable.

I did get sound.. But it was very quiet. Not the real volume of the speakers. What's up with that? I tried to check the voltage with a multimeter and it acted like it was shorting out. Maybe one of my solders was cold since it was hard to solder on to the circuit board.

I have a question. I took my speakers apart and the output is AC 9.5v. 700 mA. What can I do for this to work with a battery?? Any help would work. Please and thank you!

1 reply

A simple nine volt battery would be the simplest solution, but 6 AA C or D cell batteries would last a lot longer. To an extent, the lower voltage will only slightly lower the clipping amplitude (max volume) of the amplifier circuit. I tested the amplifier circuit in a set of sony speakers I had and the voltage was originally 12 volts, but I could get to as low as 8 volts before the sound was distorted during louder sections of music when played at normal listening levels.

i have a qesution. what are the common voltage output in transformer 2ndary, should i remove the tranformer and throw it a way?

can i ask you something?? i dont have 9 volt battery clip and a battery holder.

if you have a big enough panel, but ya might wanna put a inductor on it so that the speaker isn't broken by rapid voltage changes.

here's a video that explains in inductors:

I am pretty herp-derp when it comes to electric numbers, but could you use 6 1.5v batteries? because I have a 6 AA battery holder, and they are rechargeable too.

1 reply

yep, but rechargeables might give you less performance as rechargeables that are "1.5V" are actually 1.2V, because the chemicals that are needed to make the battery rechargeable

I have the same set of speakers as you, but cant remove the nut holding the amp board in place :/ WHAT DO I DO?!

Would this work if I just left the power supply in and wired it into this?

You should use a dry cell holder and AAs or C's because they will last longer in the long run. I tried this with some old boston acoustic speakers that got destroyed when my workbench caught fire >_< (now made of concrete..the more you know *ding*) and I needed an amp but didn't want to order parts for a chip amp. Good instructable.

on my board i saw 4 diodes in a rectifier looking like thing so i believe you can power the board with a DC battery

Tried it, on a few sets of speakers, So if you are wondering on quality, it really depends on what speakers you use. The better speakers, the better sound. Enough said.

And, why did you take it appart? wouldn't it be easier to just take the transformer out and replace it with a battery?

1 reply

 In retrospect i should have replaced the transformer with a battery, but these speakers were destined to go in a backpack.
With mine a freshly charged 9V battery lasted me about 5 hours, at about 1/4-1/2 volume. It depends on your speakers but in normal use they shouldn't draw much current.

won't you drain the 9v battery like, veeeery fast?
my transformer says: O/P:9V-1A
It's working perfectly though, sound quality is as good as with 230v from the wall^^

hey, i have similar speakers as you, i removed the board from the speakers,
and i connected 9volt battery as power source, and i conect headphones to headphone jack.
it works, but audio quality is very poor. can you tell me what might be the reason?
my speakers are old so maybe its somthing wrong with my board???
hlp pls.

man is it running in 9v battery ?? we have the same speaker but my little brother broke it but my sure the components inside is still working please help me i like to convert it to portable speakers that i can bring in my bag... haha...LOL 
but i'm serious hehe.....great thinking keep it up....