I'm tryng to build a Bubba Oscilator with TL082 Opamps, but can't get it to oscillate in the simulation. I've added an initial charge to one of the capacitors, and yet it still won't work. I've looked on the forums, but there doesn't seem to be a clear answer as to why it wouldn't oscillate. Thank you.

 

Try increasing R24 to 3meg ohm or greater. The loop gain seems to be a little low for good oscillation.

 

Didn't Change anything

 

Running simulation of Bubba Oscillator posted here.

Can anybody see the error in Fig 18 of this pdf?

 

Didn't Change anything

My LTspice simulation of the circuit (which I think is essentially the same as yours) oscillates as shown below. I used the .ic command to initially set the voltage at one of the nodes to help start the oscillation.
I added two back-to-back zeners as a clipper to limit the voltage since the generic op amp model has no inherent voltage limit and the amplitude would keep increasing indefinitely otherwise.

 

Running simulation of Bubba Oscillator posted here.

Can anybody see the error in Fig 18 of this pdf?

Cosine output taken from the wrong point?