Tubes?

[Gary Dunn]

How often should you replace the tube(s) in a preamp or amp?

[Brad Sarno]

Change them when they're going bad. Tubes in a combo amp where the tubes are physically vibrated by the chassis will age much faster. Tubes in a rack unit that's separate from the speaker will last much longer. The first thing to check for is microphonics. Tap on a tube. If you can hear it and it rattles or rings, it's probably time. Some tubes last decades, some only months. Some tubes sound cool when they've dulled with age.

Brad Sarno