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3V Amplifier - How'd they do it?

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drewlane

New Member
I built a little audio amplifier last week using the LM386 chip.

It works OK as long as I keep the voltage above 6V, but it gets kinda distorted if I try to use voltage below 6V (even though the specs say it will work with 4V). I don't know, maybe the battery is not supplying enough amps at 4V.

Anyway, I have this old portable Sony radio from about 10+ years ago:

http://www.roberts-radios.co.uk/radios/images/sony03.jpg

This thing runs off two AA batteries, and sounds great!

Any idea what kinda of circuit it uses to amplify the speaker?
I'd rather not take this thing apart as it still works, and if it ain't broken, well...

Thanks,

Drew
 

bogdanfirst

New Member
probably it ahs a transistor amplifier....
nost radios like that, especially if they are a bit older dont have ICs in them
so i think it is defientely a transistor amp inside it.
 

stevez

Active Member
The amount of sound (volume) that comes out of a speaker is dependent on the power delivered to it. The amount of power (watts) than an amp can deliver to a speaker depends on the impedance of the speaker and the voltage that is output by the amp - all of course, within the capability of the amp.

The amount of voltage that the raw amplifier circuit can deliver is somewhat dependent on the power supply voltage. It is reasonable to think that a lower voltage amp has less voltage output possible. Here is the BUT - in some amplifiers (solid state or vacuum tube) use transformers at the output that are described as impedance matching transformers. They do exactly that but for this discussion we can say that they step the voltage from the raw amp up or down depending on the requirements. So, if a solid state circuit than ran on 3 volts could deliver the power, just not at the voltage required to drive the speaker then a transformer (audio output) might be added to take the low voltage/high current signal and transform it to higher voltage/lower current. in the older tube type equipment the power supplies and resulting amp output voltages were very high but low in current. In order to properly drive a speaker an output transformer was included to transform high voltage/low current to lower voltage/higher current.

Sorry, this isn't the whole answer but might help a little.
 

drewlane

New Member
bogdanfirst said:
probably it ahs a transistor amplifier....
nost radios like that, especially if they are a bit older dont have ICs in them
so i think it is defientely a transistor amp inside it.
Does anyone have the plans of a very simple transistor amplifier that I can look at? Preferably, something that runs on 3V.

I would need a schematic and parts list at the minimum.

Thank you,

Drew
 
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