This is very frustrating

antispatula

antispatula

Active member
And really doesn't have much to do with mics, but there is no specific place to put this, and lots of people here seem to know what they're talking about, so I'll ask:

Ok, I need to read the voltage of a signal coming out of my computer.(Soundcards have a -10 db output right? Unbalanced stereo? 1/8") But I have no idea how to use these multimeters.

All I really want to know is which wires to I touch with the 2 leads?
It's a stereo 1/8". So there is the R wire, L wire, and the ground wire.
Which are the ones I touch if I'm measuring the voltage?

And secondly, What setting should I have it on if I'm trying to measure milivolts? There is a setting for both 200m and 2000m. and this is on DCV, right?

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The rest below is me ranting and not making sense. What's really important is above.

So NONE of this is making sense. I'm supposed direct current setting right?

So I put the setting at 200m, and I messed around with putting the leads on different wires of the cable. Which ones am I supposed to put the leads on?

Ok so this is what I tried: I'm using a oscillator, a 1kh tone. Since I think soundcards have a -10 db output, and I need a -18 db tone, I put the 1kh at -8, since -10 + -8= -18.

Anyways, I'd measure the vultage, and sometimes the level would increase, going from like .23 to .24 to .25 all the way up to like .4 and it would just keep going. The other time I tested, I would read the tone at like .22 and when I would TURN THE SIGNAL OFF, the level would INVREASE to like .28! Does this make ANY sense?
 
woah holy craparoni......I'm supposed to have it on AC, aren't I? When I had it on DC, I didn't get a reading. When I put it on AC, I got 4 volts, EXACTLY what I was looking for. :rolleyes:
 
glad you sorted out the AC/DC thing out. easy way to remember it: a sine wave has both positive and negative values, and so therefore must be Alternating Current..


antispatula said:
Since I think soundcards have a -10 db output, and I need a -18 db tone, I put the 1kh at -8, since -10 + -8= -18
Click to expand...


just remember that the dB is a logarithmic scale and so you can't actually add 2 dB values together in a simple 1+1=2 manner (imagine if both you're monitors pumping out 80dB resulted in 160dB hitting your face!!!). seeing as you're correlated sources (i'm assuming the L and R signal from your tone generator are the same..if they're not, you can't use this method), you have work back to the pressure level from dB (btw i'm also assuming that you're talking about dB SPL..)

pressure(pa)=20x10^-6 x10(dB SPL value/20)

if you're adding dBs, then you need to find the pressure value for each dB, add them together, and then go from pressure back to dB(SPL).
 
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