Wien bridge audio oscillator - homebrew

Here's a Wien bridge audio oscillator I built back in 2008. It uses an incandescent lamp to stabilize the gain of the feedback circuit. Search the web for the details on how and why the Wien bridge is such a good sinusoidal oscillator. From what I read, the Wien bridge circuit was used in the HP company's first product.
www.hpmemorypr...
Here's one website that explains the details of the Wien bridge,
www.electronic...
it does a much better job of describing it than I can do here.
73 Rick N3FJZ

[@arcanestudio]

Great video, Rick. Your measurement demonstrates that the oscillator purity is excellent; probably good enough for on-the-air use to generate CW. '73 Marty, K1FQL

[@beef-v5b]

Good work; Can you make it variable

[@Circuit6040]

Yes, here's one website I found that shows a variable Wien bridhe audio signal generator - see: www.eeweb.com/diy-audio-function-generator-part-1/ about 3/4 the way down the page you will see a schematic with the title "Function Generator 16Hz - 60kHz dates 4-29-20212". To make it variable they used a dual gang potentiometer (R1a and R1b in the schematic) and a 2 pole multi position switch with a range of capacitors. I hope this helps, but if not let me know and I will draw a schematic showing my version of a variable oscillator using only transistors instead of the IC OpAmp shown on that website. 73 - Rick - N3FJZ.