How can you tell when your tubes need to be replaced?

[amra]

The obvious answer would be when it sounds shitty. But here is the thing.
I have a tube amp that I hardly ever play, except for gigs or recording. I turned it on today, and gave it a good thrashing (loud enough and long enough for the power tubes to get a good glow on). Well to make a long story short, the tone sounded to me like I was running it through a compressor and squishing it - at least compared to how I remembered it. The thing is, it has been about 2 months since I played it last, so I don't know for sure if it sounds different, or if just my perception (all I have been using lately is a solid state randall for rehearsals, and amp modelers for "riffing around", and both can be a little harsh on the high end).

So what are the early signs that tubes need replacing?

[packratlouie]

I can tell you this. Some 'distortion' pedals tend to add compression to achieve their sound. So it could just be you're ear is improving and you've noticed that. If you wanna steer away from that, stick to overdrive pedals. Theres no real rule with compression, but I find that distortion pedals have alot more than overdrive.

[BigRay]

An amp that is used every day should expect to replace its power tubes every one or two years.(doesnt sound like you have that issue) If you notice lower output, strange noises, or a "muddier" tone, your tubes probably need replacing.

"Amps usually come with fuses. When a tube reaches the end of it's lifespan they become ineficient and need to draw more power from the wall in order to keep up. Eventually, they draw so much power that you'll most likely blow a fuse. If you change your fuse and it breaks again, chances are your tubes need replacing. Sometimes one or several tubes will pop and die completely when the fuse breaks. Putting in a stronger fuse can dammage your amp so don't do it!

Sometimes your amp will develop a low rumble or high whistling noise that gets worse as the volume is increased, even if nothing is plugged in. Eventually, the squeal will get so loud that it will overpower your playing. That noise is called microphony and it's a sign that your smaller, preamp tubes need to be changed soon. The constant low rumble occurs when your power tubes succumb to microphony. The low rumble occurs very rarely, usually they start blowing fuses first.

The good news about tubes is that they usually fail in sequence. If your first preamp tube starts to microphony, you may be able to temporarily fix the problem by changing the order of the preamp tubes. The first tube in the chain bears the brunt of your playing more than the others. This fix is purely temporary and you should still get new tubes as soon as you can.

If a power tube has a slight blue or purple glow it does not mean that the valve is nec"essarily faulty.............."

[Clive Hugh]

BigRay, you answered a question for me too, thanks, the tubes are already ordered.
Clive

[prestomation]

Originally Posted by BigRay

If a power tube has a slight blue or purple glow it does not mean that the valve is nec"essarily faulty.............."

What about rectifier tubes? I dont' have much(or really any) experience with tube equipment, but i have a non-guitaramp piece of equipment(old organ) loaded with tubes. The big ones(i assume are rectifier tubes) glow blue, all of them, is that normal?

Sorry for the hijack, but it looked like your question was answered