Will recording like this hurt my laptop?

[joecool85]

I have a 12" Apple PowerBook. It doesn't have a mic jack, only a line in. If you use a mic straight to that you get basically no sound (duh). So, I've been using my little gem 1/2watt guitar amp as a preamp. I plug the mic into that, and then use the speaker out on that into my laptop. I monitor the levels on my laptop making sure I'm not peaking too much.

Here is the schematic for the little gem:
**broken link removed**

 

[Nigel Goodwin]

No, it should be no problem, the voltage output of the amp won't be very high anyway - if you really want to feel safe though, feed it via a resistor to the laptop.

 

[joecool85]

What would be a safe voltage to run into the laptop? I've heard lineout voltages can vary from .5volts to 2 is that right?

Also, to test the voltage, can I just hook the positive of my multimeter to the + on the speaker out, and - to ground?

 

[Nigel Goodwin]

What would be a safe voltage to run into the laptop? I've heard lineout voltages can vary from .5volts to 2 is that right?

That range sounds about right!. Your laptop should handle those no problem, a tiny amp like that dosn't have enough ouput to damage anything. If you like, insert a 10kohm resistor in the signal lead.

Also, to test the voltage, can I just hook the positive of my multimeter to the + on the speaker out, and - to ground?

No, you need an AC millivoltmeter or a scope.

 

[joecool85]

Well, I have this one: https://www.radioshack.com/product/index.jsp?productId=2104114&cp=&kw=multimeter&parentPage=search

And it read between 2.5 and 3.5 volts for the levels I had been recording at...seems a little high to me. So I may need to use a buffer or something at the end of the circuit.

 

[joecool85]

Ha, I'm fine. Here is what I found out for my laptop:

maximum input signal amplitude 2 Vrms (5.65 Vpp), +8 dbu peak