Ok, I think you guys are missing my question.
I realize that the positive feedback loop has a gain of 1/3 at the freq of the filter. I realize then that the gain of the amplifier needs to be 3 to get the ~unity gain needed for stable oscillation.
But these are fractions, not absolute values. I want to know how to predict the exact output level for known Vcc (and any other variables I might not know are relevant).
For instance, I currently have a WB on my bench running on a +/- 6V supply. I have a 1 k resistor as my feedback resistor, and I have the bulb in series with my decade box currently set at 447 ohms. This value gets me the purest sinewave. The harmonics are barely above the noise, at least on the low brow FFT my 1054z offers. My filter loop is 470 nF caps, and 10k resistors. I get 35ish Hz, which is pretty close to the math, and even closer with the actual measured values of the parts.
I am getting an 8 volt PtoP signal at the output. (actually, at the output of the opamp buffer I have it going to).
With that info, how might I have predicted specifically the 8 volts? Opamp is a tl072 if its relevant. I do see that 8 is 2 thirds of my supply, which the back of my brain says is a clue. Is it as simple as that?