Just making sure...

[Kingofpain678]

Ok, So when using a multimeter in the studio to determine if your signal is at line level you set the multimeter to AC Volts and...
+4 dBU = 1.228V
-10 dBU = 245mV

Correct?

 

[Kingofpain678]

Bump?............

 

[Chili]

I'm not up on the details, but you would have to drive the signal with a known source, like 1khz at a specified level, then measure the voltage across a specific resistor (1K ohm???). Then you would be looking for the RMS value of the voltage.

And also, the standard for pro (+4dbU) and consumer level (-10dbV) are different scales. Pro level is dbU (notice the U) and consumer is dbV ( notice the V). The Pro level uses a reference voltage, something like 1V rms and consumer level is a measurement of voltage itself.

I can't remember the details, but it's not a straight measurement off you output jack. However, the manufacture of your equipment did their homework and put it in the manual. You should check that. Or are you doing this to learn a little more about the tcehnical end of audio??

peace,

 

[timkroeger]

I had to check up on that recently to calibrate my tape deck and found the following explanation on bnoack.com quite useful:

To describe an absolute value, the reference point must be known. There are different reference points defined. dBV represents the level compared to 1 Volt RMS. 0dBV = 1V. There is no reference to impedance (V = Volt). dBu represents the level compared to 0,775 Volt RMS with an unloaded, open circuit, source (u = 'unloaded' or 'unterminated' -- a voltage that is not related to power by an impedance). dBm represents the power level compared to 1 mWatt. This is a level compared to 0,775 Volt RMS across a 600 Ohm load impedance (m = milli).

There are several tables on the page for dBV - voltage ratio and dBu voltage ratio which puts +4dBu at 1.2277V (RMS) and -10dBV at 0.316V. I'm not sure on how to measure it, but I'd just measure it unloaded. Please someone correct me, if I'm wrong here. You'd need a true RMS meter and make sure that the signal you're measuring doesn't have a DC offset since most "True RMS" meters (even the more expensive fluke meters) just calculate the squareroot of (peak to peak voltage) / 2.

Hope that helps
Tim