I've got to analyze an electronic metronome schematic and I'm having trouble understanding how the oscillator in this schematic really works.
I believe it's a Wien oscillator with variable output wave frequency. Diodes in negative feedback loop are used for amplitude stabilization and output should be a half-wave rectified sine wave (only positive half-waves because of the opamp power supply) if I'm not mistaken.
But I'm wondering what do resistors R15 and R16 in parallel with capacitor C7 do? Are they just used as a voltage reference, or are they used for something else?
I assume that variable resistors are used to set frequency of the oscillator. Do I use Barkhausen equation to calculate the frequency based on the resistance of variable resistors, or is there an easier way to do it?