# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/Db0qWhQA7zR
- **Gondola URL:** https://gondola.cc/posts/69054414-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/aa864b7aec.jpg
- **Posted:** 2026-08-09T14:34:35.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

The music is not coming from a speaker. The lightning is the speaker.

A Tesla coil is not a transformer in the usual sense. It is a pair of tuned resonant circuits coupled loosely through air instead of iron, and the voltage gain comes from resonance rather than turns ratio.

- Primary: a few turns of heavy copper tube in series with a capacitor bank, low inductance, huge peak current
- Secondary: thousands of turns of fine enamelled wire, resonating against its own distributed capacitance plus a toroidal topload
- Both tuned to the same frequency, 50 to 500 kilohertz

Energy transfers between the two tanks each ring cycle. Terminal voltage climbs until the air can no longer hold it off, roughly 3 megavolts per metre, and a streamer punches into the room.

The musical part is a modulation trick. A dual resonant solid state coil drives the primary with an IGBT bridge, locked to the ringing frequency by current feedback. That carrier sits far above hearing. Sound comes from an interrupter gating the bridge on and off in bursts.

- Burst repetition rate sets the pitch, so concert A is 440 bursts per second riding on a carrier of a few hundred kilohertz
- Burst on time sets arc length, which is also loudness, so dynamics and streamer size are one control
- Each burst heats the plasma by thousands of kelvin in microseconds, the air expands and collapses, and the result is a pressure pulse

The arc is a diaphragm with no mass and no enclosure. Because every note is a train of sharp impulses rather than a smooth sine, the timbre is harmonically dense and unmistakably buzzy. Polyphony is the hard part: one channel, one arc, so voices must be interleaved within limits set by IGBT junction temperature.

Scale it up and you reach Electrum: 11.5 metres, 130 kilowatts, 3 megavolts, built in 1998 by Eric Orr and Greg Leyh.

Tune two circuits to the same note and the air will sing whatever you interrupt.
#stemantics #teslacoil #highvoltage #electricalengineering #plasmaphysics

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## Tags

teslacoil, plasmaphysics, highvoltage, electricalengineering, stemantics

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