# sound card

Discussion in 'General Electronics Discussion' started by mahin, May 2, 2012.

1. ### mahin

11
0
May 2, 2012
hi everybody,
i want to know output current and voltage of audio jack in PC, how can i measure them,
thank you

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,839
Jan 21, 2010
It's a bit of a Schrodinger's cat type of question.

You can't measure one without affecting the other.

For example, you might short out the output and measure 100mA. And then you might measure the voltage and see 2.5V RMS. From that you might (incorrectly) assume you can draw 100mA at 2.5V. But the voltage was measured at zero current, and the current at zero voltage.

To really answer the question you need to define a load (say a 33 ohm resistor) and measure the voltage across it and the current through it.

On another level, you also need to consider the source of the signal and the volume level. In this case it will have a substantial effect.

If you know the rating of the output in watts (or in this case probably milliwatts) you can calculate the relationship between voltage and current. What the amplifier can do at its best will be a point on that curve.

For your amplifier, lets say it's rated at 150mW, that means it may be capable of delivering 75mA at 2 volts. But note that this is one point on the curve, and not necessarily the one the amplifier can reach (for example, you wouldn't expect 1mA at 150V or 15A at 10mV)

Now, remember I said you have to read the voltage across the load and the current through it? Actually that's a lie. From the voltage across it we can determine the current through it (for a simple resistor). But is either case (measure or calculate) you will come up with a voltage and a current.

3. ### mahin

11
0
May 2, 2012
thank you, i want to use output jack of sound card as input in rectifier and then output of rectifier to input jack for seeing signal at monitor,
can i do this?

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,839
Jan 21, 2010
Sure, you can do it. I'm not sure why you want t do it (so I can't comment on whether it would achieve what you want).

And what is your monitor? An oscilloscope?

5. ### mahin

11
0
May 2, 2012
i want to use it as generator and oscilloscope togetherutput(speaker) as generator and input(mic) as oscilloscpe. i have a program that can display mic jack on monitor such oscilloscope.