Quote:
Originally Posted by originalscottyg
My understanding is that the Signal Generator plugin allows you to select dB-RMS or dB-PEAK. These are the same for a pure sine wave, but different for more complex waveforms. When measuring voltage with a DMM, you are generally measuring Volts RMS (TrueRMS on a Fluke). The dBFS (peak) value of -20 or -18 will be referenced to an RMS voltage value at the converter output, in this case +4dBu or 1.228VRMS.
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No. Time to revisit basic definitions. Which is where I started here. If you remember what things actually are you can just calculate and do anything you want.
Vrms and Vpeak is not the same for a sine wave. Vrms is the equivalent power that would be delivered if the signal was DC into the same impedance.
You integrate over all the different signal patterns and can work out the difference for each between Vpeak and Vrms. Which gives...
Sine: Vrms ~0.71 Vpeak ~ -3 dB
Square: Vrms = Vpeak = 0dB
Triangle: Vrms ~ 0.58 Vpeak ~ -4.7 dB
Ramp: Vrms ~ 0.58 Vpeak ~ -4.7 dB (same as a triangle, you can argue this via symmetry)
And be careful if you are measuring Vpeak or Vpp on an oscilloscope.
Just play with the signal generator and you can see what is happening. If you set 0dBFS peak all the waveform signals exactly hit the digital extremes. If you then change to rms the signals (except square wave) will clip, by varying amounts, the exact dB differences above. Look at waveform levels, don't get confused by different Pro Tools meters.
But again, the original specific question is actually simple, if the goal is to get an internal dBFS signal and compare it to an external level. You just work in peak.