How long do tubes need to be burned in?

The burn-in time of tubes in the audio sector varies greatly and can range from just a few hours to several hundred hours; however, it is usually assumed to be around 50 to 100 hours. The reason for this is the expansion of different materials, such as metals and glass, as well as the vacuum, which is improved by the getter — the silver-colored mirror inside the glass.

After burn-in, the vacuum is better, the materials have found their final position, the sound becomes calmer, spatial imaging improves, resolution improves and the sound becomes more structured. Most tubes are already burned in, or formed, by the manufacturer for several hours at the factory for basic use.