Speakers & amplifiers

[Swiz1611]

Maybe somebody here can help me out with this so whatever tips or advice you can give me will help a lot so here it goes.

I acquired two small amplified speakers from an old computer. I can't find who makes these speakers at all. The name on them is (EP-280/Amplified Speaker System). No serial number, model or anything.

The speakers had a bad hum so I decided to take it apart and fix the hum but became intrigued and wanted to know how to build the small amplifier attached to the circuit board. I can read and figure out schematics and componets which I have already. The problem I have now is I don't know the size amplifier schematic to build to test with the small speakers. There is no impedance or wattage printed any where on the speakers. I want to build the entire amp circuit board from scratch and hook them up to the speakers. I tried figureing out the circuit board that was already in it but lost track of the componets hook ups, became ****ed and soldered everything off of it.

Does anybody have any ideas or advice on how I can start this out? I want to build the amp but I don't know the size amp to build because I can't figure out the wattage of my small speakers or the ohm load. They are real small speakers so this is not a lot of power here. The speaker size is approx. 3 in. I also took the transformer out (assuming a step down transformer) and don't know how to measure the voltage coming out of the transformer. any tips on that also?

Any help or suggestions would be great Thanks

-Justin

 

[Nigel Goodwin]

Probably only 2 or 3 watts - to measure the output of the transformer use your meter on AC volts, you're probably looking at 12-15V?, or less.

 

[Sceadwian]

If there was a bad hum on them then the amplifier itself was probably cheap so that means the speakers were cheap, 2-3 watts might even be pushing it. But you at least have a ballpark. It's not always bad to overbuild an amplifier though, as long as you're cautious with the volume control, a higher wattage amplifier using a lower volume setting on lower wattage speakers will generally sound better than an amplifier turned up to 8 or 9 to get the same output power. Just don't turn the higher wattage amp up on lower wattage speakers or you'll blow the cones, or burn out the voice coil. If you expect a 2-3 watt speaker. I'd say using a 5 watt amp would be a decent goal, requires an ear for clipping when you turn it up though, you'll hear the distortion when the speaker starts reaching it's physical boundaries long before the speaker blows as long as you don't feed it any bass spikes.