# tubes done?



## ccuwan (Jul 9, 2008)

How do I know if I need to change my tubes? The deterioration of a tube is like watching you kids grow. If you see them every day you don't notice them grow. 

How do I recognize when they need to be changed. Do they distort, lose power or get muddy sounding etc. Fact is, I've had the same tubes for more than a year so I'm guessing they should be changed but how do I know. Frankly my amp sounds pretty good to me but maybe that's because my ears suck. I'd hate to drop $100 to find out there was nothing wrong with the old tubes or worse still they sound better than the new ones.

Do preamp tubes wear at the same rate and are their age weaknesses the same as power tubes?

Thanks Ray


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## Wild Bill (May 3, 2006)

ccuwan said:


> How do I know if I need to change my tubes? The deterioration of a tube is like watching you kids grow. If you see them every day you don't notice them grow.
> 
> How do I recognize when they need to be changed. Do they distort, lose power or get muddy sounding etc. Fact is, I've had the same tubes for more than a year so I'm guessing they should be changed but how do I know. Frankly my amp sounds pretty good to me but maybe that's because my ears suck. I'd hate to drop $100 to find out there was nothing wrong with the old tubes or worse still they sound better than the new ones.
> 
> ...


It's easy when you're a tech, Ray. I must have at least 5 tube testers around the place!

As a player, first off you shouldn't worry about the preamp tubes. They amplify voltage and thus don't see hard wear. They can go wonky but normally they work until they die and that can be a LONG time! I've pulled 12AX7's out of equipment that were at least 50 years old and they still worked just fine.

Power tubes are different. They handle current and that wears tubes out faster. Also, modern tubes don't always seem to be as tough as ones built in the golden years. Still, if they were biased correctly when installed they should last at least a couple of years, depending on how much you play. If you played a few hours every day then a year or two at least would be normal. If you played less then the tubes would last longer.

That being said, if the bias was off the tube life could suffer a LOT! And sometimes even a good brand of tubes might deal you a poor pair that conked out early.

How can you tell by ear? Usually, if the amp is still good and loud then the tubes are ok. Tone doesn't suffer nearly as fast as gain. When the gain drops off the amp just can't deliver the power.

I tell my customers that after I set them up with new output tubes that I've biased up they should maybe come back in about 18 months or so. I'll charge them a minimum hour's time to check and if necessary re-bias the tubes and I will also run all of them through a tube tester. If the output tubes test fine then run 'em for another year and a half!:rockon2:

This also gives me a chance to poke around in the amp, check the voltages and look for anything getting crispy or something.

Others may have different opinions but this works for me.

:food-smiley-004:


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## GuyB (May 2, 2008)

I have another question related to this topic : when you have an amp that can be used in 15W or 50W (like my Traynor YCS50), there is only one power tube working in the 15W mode. So, if it's always the same tube that is working, it will not last as long as the other one. What can this do on the tone or on the overall functionning of both power tubes (bias, longevity, can you hear the difference when a tube is much "older" then the other) ?


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## aC2rs (Jul 9, 2007)

I can tell when the power tubes in my amp go as the amp makes bad noises followed by dense fog and poor air quality.


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## ccuwan (Jul 9, 2008)

Again WB....thanks for the great information. You obviously know exactly what you're talking about and answer my questions not only with facts but with explanation.....I appreciate that as I'm much more inclined to listen when I understand. 

Ray


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