Quote:

Originally Posted by **mogWai**

Ok, I have setup MDA TestTone and PSP Vintage Meter in Cubase.

I am vaguely familiar with the PSP Vintage Meter, but what is

*MDA TestTone* ?

Quote:

Originally Posted by **mogWai**

TestTone is running a 1kHz sinewave at 0dB, TestTone also set to 0dB = 0dbFS.

Ok, here is an opportunity to clarify this dB business. dB is an abbreviation for decibels. Decibels are a logarithmic measurement, which means they are not a linear measurement. 1+1=2, but 1dB+1dB != (the "!=" means does not equal) 2dB. Decibel measurements are always referenced to a nominal operating level, which is defined as 0 dB. Not only are decibel measurements referenced to a nominal operating level, but they are also referenced to another measurement! To truly understand a measurement expressed in dB, you need to know...

1. The measurement that is being referenced to.

2. What the 0dB value of the referenced measurement is.

Read on and I will address these points.

Quote:

Originally Posted by **mogWai**

PSP Vinatge Meter set to VU shows this tone to be 0dB... is that 0dBU on a VU meter??

This is most likely 0dB VU. dBu (yes, capitalization matters) is a measurement referenced to voltage. If a measurement is expressed in dBu, then it is referenced to 0dBu, which is defined as 0.775 VRMS (voltage measured using root mean square). The

*u* in dBu means unloaded (high-impedance circuitry sees low impedances connected to them as negligible, which is essentially unloaded - no load connected). I will not go into RMS measurements, as that would sidetrack us from your initial goal (though you should strive to understand that concept too).

Quote:

Originally Posted by **mogWai**

Cubase channel and master faders show -12db (dbFS?)

You would have to RTFM for Cubase to know for certain what ballistics those meters use. If they use the same ballistics as other channel meters in other DAWs that I have used, then yes, the scale would be dBFS. To tie dBFS into the lesson, a measurement expressed in dBFS is referenced to

**F**ull

**S**cale digital, with 0dBFS being the greatest signal value that can be represented in the digital realm.

Quote:

Originally Posted by **mogWai**

I have reset the Rosetta200, and this tone appears to be -16dbFS.

The Rosetta 200 ships with its calibration set to -16dBFS according to TFM.

Quote:

Originally Posted by **mogWai**

The Master VU meters on the Topaz I have set to 0dB (dbU?) using the gain pots with the channel faders at 0. (there are no calibration levels on the Topaz Gain pots!)

Forgive my ignorance, but I do not know what a Soundtracs Topaz is. However, I can still help you.

Again, just like the PSP meter, this is most likely 0dB VU. Since there are no markings for the trims on your Soundtracs Topaz, it is wise to have the faders at 0dB (unity gain) for this process.

Quote:

Originally Posted by **mogWai**

So I have many questions.

I hope I have many answers.

Quote:

Originally Posted by **mogWai**

Does the Rosetta need to be calibrated to show this level as -12dbFS?

Yes. This results in your signal chain having unity gain. At the moment, you are losing 4dBFS between Cubase and your Rosetta. Think of it as having a fader between Cubase and the Rosetta. If you did, in your current setup, said fader would be -4dB below unity (0dB). Since the goal of calibration is to have every device operating with unity gain, you need to calibrate your Rosetta. The procedure is in TFM.

Quote:

Originally Posted by **mogWai**

If -12dbFS = 0dbU then my VU meters are going to be hopelessy pinned whenever I am mixing, since then I push 0dbFS...

That problem is outside the scope of simple calibration. If the VU meters will be hopelessly pinned (which damages them, by the way), then either change your mixing style or don't bother using them.

Quote:

Originally Posted by **mogWai**

Can someone, anyone help me makes sense of all this level stuff?

I hope I just did.

Quote:

Originally Posted by **mogWai**

Where does +4dbU fit into this equation.

+4dBu (remember, capitalization matters) means that a device is operating at 4dB above (hence the + sign) 0dBu, which was defined above as being 0.775VRMS. The

*u* was defined as meaning the high impedance circuit has no load connected. So if 0dBu = 0.775 VRMS, then what voltage is represented by +4dBu? This is where the log and anti-log keys on your calculator become useful. The formula for calculating voltages with logs is dBu = 20 log (base 10) Vo/Vi where dBu is the reference value, Vo is the output voltage, and Vi is the input voltage. We know that 0 dBu = 0.775VRMS, so to determine what voltage corresponds to +4dBu, we calculate it as

4 = 20 log (base 10) Vo/Vi

4÷20 = log (base 10) Vo/Vi

.2 = 10 log (base 10) Vo/Vi

Now we take the anti-log of .2 This can be thought of as raising 10 to the power of .2.

10 anti-log .2 = Vo/Vi

1.585 = Vo/Vi

Now, we know the input voltage is 0.775VRMS, so

1.585 = Vo/0.775

1.585*0.775 = Vo

1.228VRMS = Vo

We have just calculated that audio equipment whose nominal operating level is specified as +4dBu operates at a nominal voltage of 1.228VRMS! stike

What are the implications of this? Well, besides learning some math, you now know that if your audio interface outputs, Rosetta I/O, and Topaz inputs are all specified to operate at a nominal level of +4dBu that you could use a voltmeter at each point in the chain to verify that everything is operating at unity gain by checking to see that the voltage is 1.228VRMS.

Quote:

Originally Posted by **mogWai**

Just trying to learn something..

I hope you did. This was a nice refresher course for me as well.