[stump4545]

If tubes in my modwright 36.5 DM pre amp  start to go, do they just die a fiery death, or is it possible that they can emit an intermittent humming ground loop type of sound?

thank you

[paul79]

Yes, tubes can hum if they are micro. I can always hear when signal tubes get bad enough, so never experienced a fiery death so to speak. Signal tubes lose focus when they start wearing out, or become noisy or hum. If you are using new production tubes, I would just change them out every couple years or so. Old stock tubes can last a lifetime though, but you will pay for it.

Rectifier tubes can short, open, flash over, etc, but they are typically good and strong until they die. Same for large output tubes.

[FullRangeMan]

do they just die a fiery death,

Each case is different, there is no a pattern of behavior depends on each tube, quality reliable tubes have a benign death, sound have a change when tube get old.

[avahifi]

The reason very old tubes change sound is because as they age their gain goes down so distortions in the circuit goes up.

No magic, easy to measure with a distortion analyzer.

Frank

[Adarsh]

Yes, tubes can hum if they are micro. I can always hear when signal tubes get bad enough, so never experienced a fiery death so to speak. Signal tubes lose focus when they start wearing out, or become noisy or hum. If you are using new production tubes, I would just change them out every couple years or so. Old stock tubes can last a lifetime though, but you will pay for it.

Rectifier tubes can short, open, flash over, etc, but they are typically good and strong until they die. Same for large output tubes.

Can you please explain what you mean by "micro"?