One of the devices with the lowest breakdown ionization potentials is the neon light. There was one version sold by Radio Shack that broke down at about 50 volts. With a resistor and a capacitor you could make it pulse. The voltage built up on the capacitor and the lamp pulsed discharging the capacitor.
I tried to employ this negative coefficient of resistance to make an amplifier. The pulsing operation is actually an oscillator, perhaps it would oscillate at audio frequencies. I had no luck with this idea. The bulb glowed dimly. This was not a bright idea! Anyway is fun to play with and learn about glow discharge arcs. As before, I had none break down at less than 50 volts. Today I am making apps. My latest app Video Selfie Start / Stop is now running a paid advertising complain. https://www.amazon.com/Znidarsic-Science-Books-Video-Selfie/dp/B076WMXB99/ref=sr_1_2?s=mobile-apps&ie=UTF8&qid=1511638214&sr=1-2 I have had about a quarter of a million impressions issued. Of that at I got about 500 hits. I sold one app. Its is really hard to do anything, is it not! frank