Wien Bridge oscillator

Hello, I'm doing some work with Wien Bridge oscillators and having a look at some of theory.

Apparently oscillation occurs at the resonant frequency = 1/2*PI*R*C

However, if you apply the Barkhausen criteria for oscillation you get a completely different expression for oscillation frequency, in my case f = 1/R*C

What is the difference between the two?

Thanks!

Stare at this:

At what frequency is the phase shift exactly 0 degrees?

What is the loss (in db) at that frequency?

Relate that to the formulas you posted.

Notice what happens if the Wien network is connected to a non-inverting amplifier with gain slightly higher than 3 (9.54db), and is given an initial perturbation.

Thanks a lot MikeMl, those were really helpful. I feel stupid for asking the question now, having woken up feeling (relatively) refreshed, I can see that one expression simply gives the oscillation frequency in Hertz and the one I derived gives it in Radians... D'Oh!

Thanks again MikeMl!