How to build a circuit that generates a sine wave?
DDS chip + filter is one way that's pretty common these days. 

You can try to round off and then filter triangle waves with diode or active circuits. 

At 72kHz, an LC oscillator would not be bad (wind your own high quality inductor or tapped inductor on a pot core if you like) and pair it with quality PPS or other film capacitors.  

Or a Wien bridge oscillator. 

If you want low distortion with an LC or Wien bridge you need to have a good AGC that controls the output level without adding too much distortion (so it will necessarily take many cycles to stabilize).