Tube Life

dcarlson

I was just wondering how do you know when it's time to replace tubes?

madmax

If I were a tube I would want to be replaced when I started spitting and making funny sounds.
madmax

Tour2ma

If that were true, I'd have been replaced decades ago...

dcarlson

Spitting as in a funny sort of wandering static coming from one channel after an extended period of play?

How do you figure out the upper volume limits a tube amp reach? I'm just not sure how hard I can push and I don't want to push too hard.

madmax

With tubes the upper limit is pretty apparent. The sounds start getting all jumbled up. Stop and set back a notch if that happens.
madmax

madmax

Originally posted by Tour2ma
If that were true, I'd have been replaced decades ago...

Sure, you have some time after that starts happening. I just hate being spit on.
madmax

O'Shag

When the performance deteriorates, most noticably sounding dry or flat, then it will be time to replace the tubes.

Power tubes generally have a life expectancy of about 3000 hours, and tubes in the output stage 5000-6000 hours. A lot depends on how the tubes are biased, how much power is set to be drawn from them during operation, and how they are managed in terms of heat (heat is the main factor attributable to the shortening of tube life). Some tweakers have designed small heat sinks to fit around tubes resulting in quadruple the lifespan.

The downside with tube technology is the maintenance cost associated with replacing tubes which will be anywher from $300 about every 5 years, dependent on how much the system is used. If left on 24 hours a day, tube lifespan will be shortened.

The upside, is that good quality tube gear, will reproduce music much better than all but the most expensive solid state Class A amps.

Several years ago I thought all this tube stuff was hype, after all how could an older technology sound better than modern solid state technology. That was befor I listened to one of my friends systems. At first listen, I knew that tubes were for me.

Besides tube power amps and preamps, I also own a Carver SD/A 390t CD player with two 6DJ8 Amperex Bugle Boy tubes in the output stage. It is one of the very best CD players I have ever heard and I've listened to very expensive CD players. Other Carver CD players were mediocre at best(non-tube), but the little known Carver SD/A390t is a total gem.

By the way, how are those Amazings? I hear they are difficult to drive, but really superb.

Tour2ma

Haven't any of you North of the Border guys invested in a tube tester yet? I mean, with no hockey in the offing, you'll have some time on your hands...

dcarlson

Originally posted by Tour2ma
Haven't any of you North of the Border guys invested in a tube tester yet? I mean, with no hockey in the offing, you'll have some time on your hands...

Ha! I know Maurice was thinking of getting one. I'm not as much of a tubehead just yet.

Without hockey, it IS going to be a long winter, maybe I'll have a chance to build the bottlehead Foreplay that's been sitting in a box for the last few months.

O'Shag,

Welcome to the forum and thanks for the info. Looks like you have the "Disease".

O'Shag

Thanks for the welcome D,

Yup, I am hopelessly addicted. Ridiculous really, but there's no point trying to explain the virtues of a good pair of Tube monoblocs to someone who doesn't have the affliction, they live in blissful ignorance (lucky them) as to how massively much better this type of gear sounds than your average run-of-the-mill stuff out there.

Can you imagine, its even got me fibbing to my better half, (like a coke fiend trying to fund his next hit). "You got a new piece of equipment did'nt you?" "Oh that love?, that old thing just cost $50 bucks". (when in reality it set me back $1000). I don't feel too bad though, because I know she does the same thing when she goes shopping for clothes and make-up. Shes starting to love my system too which is great. That way I can justify further 'investments' to her.

I'm sort of kidding though, because its worth it, wouldn't you agree?

HBombToo

Originally posted by O'Shag

Power tubes generally have a life expectancy of about 3000 hours, and tubes in the output stage 5000-6000 hours. A lot depends on how the tubes are biased, how much power is set to be drawn from them during operation, and how they are managed in terms of heat (heat is the main factor attributable to the shortening of tube life). Some tweakers have designed small heat sinks to fit around tubes resulting in quadruple the lifespan.

I agree that rectification tubes will have a shorter life by leaving the unit powered up. Its obviouse in this case.

I would like to suggest that in preamp_amp/cd type of application where there is no real draw unless the circuit is active then life should not be degraded substantially. I believe that through a tubes life span that expansion/contraction by turning the unit on and off could have a far greater negative impact on a tubes life. Through many cycles of expansion and contraction the precious vacuum could be lost and then your off surfen for new tubes.

HBomb

O'Shag

Hbomb - good point
No doubt that the switching on and off of tube-based equipment will have some impact over time. Others believe this negative effect is outweighed by the deterioration prolonged high-heat will cause during continual operation i.e. when the unit is left on even when not in use. I have a lot to learn about tube operation, but from what I can gather it seems to depend on how different manufacturers approach power output. A key factor to consider is what percentage of total power capacity is being used during operation. Commonly, manufacturers will set their tubes to perform near maximum output capacity. The more ambitious try and squeeze every last drop of power available, with the inevitable downside.

My Carver SD/A390t has two Amperex Bugle Boy 6DJ8s running in the output stage, but these tubes are only operating at 25% of their maximum output capacity. Bob Carver wisely did this to insure that performance characteristics will not diminish for a very long period of time. Whats amazing is how good the player sounds even with the tubes running at only 25%.

In contrast to this, my ARC Classic 120 monobloc tubes are operating at a much higher percentage of their total output capacity. They will inevitably give up the ghost in another three years or so at which time it will be necessary for me to fork out about $500.00 to replace all the tubes. For my perspective, thats a price I'm willing to pay for their superb performance.;)