Int Spkr to Line Out circuit

[kiyotewolf]

This is my circuit to go from internal speaker (or piezo dot speaker) to Line Out.

The circuit matches the impedance of what the motherboard expects, as well as gives you control so you don't overdrive the input of your amplifier.

Parts list.:

1. a small blank PCB board
2. a 1k(ohm) to 8(ohm) audio transformer
3. a SPDT switch audio potentiometer
4. RCA jack or phone jack
5. someone who can solder & read schematics



I'll give you the words to do this with less parts as well.

Buy the radio shack audio transformer. On the 8ohm side, connect the leads in place of the audio speaker or piezo speaker (that means desoldering the piezo speaker and putting wires directly on the motherboard). Connect the leads on the 1000 ohm side to your audio jack (headphone wire). Hook up the jack to a headphone audio level control (those little things with knobs for your headphones they sell) to adjust the volume.

There will be either 1 or 2 extra wires on the transformer. They are center tap wires. insulate those and do not use them. Make sure they don't attach anywhere. Check the diagram on the Radio Shack item to see which wires are the outside wires.

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Taking the piezo speaker off the motherboard and using this circuit does work. I did it on my own motherboard.


[pc] -> 8ohm side [transfomer] 1k side -> [audio jack]

Because the transformer doesn't worry about which leads are hot or grounded, you don't have to worry about getting which wires right or backwards. The transformer electrically insulates the outside world (amplifier) from the PC, so you don't have to worry about it.



Kiyote!

@Trixster ~ you can post this on your site as another alternative

[Trixter]

Awesome, I will, thanks!