Nixie or Numitron — Which Clock Should I Buy?
How the two technologies actually differ physically
A Nixie tube is a cold-cathode gas discharge device: a sealed glass envelope filled with low-pressure neon (sometimes with a trace of mercury or another gas to alter the colour), containing a wire-mesh anode and a stack of individually shaped cathode wires, one per digit. Apply roughly 170–180V DC across the right cathode and the neon around it ionises and glows orange-red. Driving one needs a boost converter to generate that voltage from a low-voltage supply, plus a driver IC or transistor per digit to switch each cathode.
A Numitron tube contains no gas at all. It's a set of fine tungsten (or similar) filaments, bent into the shape of digit segments, sealed in a small evacuated or inert-gas-filled glass envelope — functionally a miniature multi-segment incandescent bulb. It runs directly on a few volts DC per segment, the same low-voltage domain as the rest of the board, with no boost converter and no high-voltage anywhere in the circuit.
Glow character and brightness, dark room vs daylight
Nixie tubes produce a sharp, saturated orange-red glow with a distinct discharge structure around the lit digit, which is the look most people associate with the word "Nixie clock." It reads clearly even under normal room lighting. Numitron filaments produce a softer, warmer, dimmer glow closer to an old incandescent dial lamp than a neon sign — it's an appealing, low-key look, but it is more of a low-ambient-light display than a Nixie is; in bright daylight the segments are harder to read than a Nixie's discharge glow.
Reliability and lifespan trade-offs
Nixie tubes have a well-documented lifespan story: at rated current, well-made tubes commonly reach 15,000–25,000+ hours, but they are also susceptible to cathode poisoning if a digit sits static for very long periods without ever cycling — see How Long Do Nixie Tubes Actually Last? for the detail on that failure mode and how it's mitigated. A Numitron filament doesn't suffer cathode poisoning at all, because there's no gas discharge to poison — its failure mode is the same as any incandescent filament, which is an extremely well-understood and generally very long-lived mechanism when run within its rated current.
The other side of that trade-off is component count: a Nixie board needs a working HV boost converter and driver stage on top of the tubes themselves, which is one more subsystem that can develop a fault. A Numitron board only has the low-voltage segment drivers, which is a simpler circuit with fewer things to go wrong independently of the tubes.
[Ian: worth adding here — the actual power draw comparison between your Nixie and Numitron models, and which specific Numitron products you currently sell, since only two exist today (4-digit and 6-digit) versus a much wider Nixie range. Any real-world failure-rate difference you've observed between the two across the units you've built would also be strong material for this section.]
Which one to pick for your use case
- Want the classic, unmistakable "Nixie clock" look, don't mind an internal HV stage, and want the widest choice of tube types and clock models? Go Nixie.
- Want a warmer, quieter glow, the simplest possible electronics with no high-voltage anywhere on the board, and are happy with a smaller model range? Go Numitron.
- Displaying it somewhere bright (a well-lit office, a shop window) favours the Nixie's stronger glow; a bedside table or a dim room lets a Numitron's softer light shine without being overwhelming.
Numitron models: 4-digit Numitron clock and 6-digit Numitron clock. The full Nixie range, across tube types and formats, is on the main store page.