Author Topic: valve / tube life span ??  (Read 700 times)

Offline ronman

valve / tube life span ??
« on: August 10, 2018, 03:56:27 PM »
Hey chaps

I had a globe in my store room which did its job reliably for years. Light the room. Until a ladder accidently whacked the fixture and shattered the globe. It was only after a matching globe (same brand and same purchase date) was installed did we realise how dull that previous globe had become during its use. I use this example of the globe as, to me, a globe and a hifi valve / tube are similar as they both emit heat, light and pass current. Reason behind this line of thinking is for years I have heard stories of tubes degrading with every use, and that these are having to be constantly swapped out. To me, as a tube noobie, that sounds like a headache. Is this true when they are used in a pre-amp / music situation? Does the music become less so because of an "aged" tube? Do I need to stockpile a collection of potentially delicate tubes to maintain the level of musicality I am enjoying now, or do I stay with quality solid state that has never failed me. I recently got a Woo Audio headphone valve pre-amp, and as lovely sounding as this little thing is, these "worries" now shadow my enjoyment of it.
Any thoughts or opinions based on your experiences would be greatly appreciated.

Offline Curlycat

Re: valve / tube life span ??
« Reply #1 on: August 10, 2018, 05:33:29 PM »
Live in the now  ;D and let your Woo woe you.

I will happily spend money on replacing tubes because I much prefer the sound of tubes in a pre as appose to solid state. Rolling tubes allows you the opportunity to change the character of the sound as well. Generally speaking, preamp tubes last much longer than power tubes, but always good to have some backup tubes available.

Offline Steerpike

Re: valve / tube life span ??
« Reply #2 on: August 10, 2018, 06:05:18 PM »
Valve life is VERY dependent n the circuit it is used in. An ECC83 used in a hi fi preamplifier will last WAY longer than an EL34 used in a guitar amplifier.
Typical lives are 1000 hours to 10,000 hours or even longer for special quality editions.

Different cathode materials also have different life spans.

Even so, a good circuit is designed to minimise the effects of valve ageing. Up until the point of failure, you should not notice a salient change in performance as the valve characteristics slowly change.
That was good design technique in the 1950s and 1960s where a product had to last to maintain the good reputation of the company - modern 'fashionable' designs may place less emphasis on long term reliability.

Offline JonnyP

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Re: valve / tube life span ??
« Reply #3 on: August 10, 2018, 07:47:33 PM »
Tubes are like that favourite armchair.  It started out new and a little edgy and standard.  After a year, it had molded to your frame and the table you take your drinks from.  After 10 years it feels like part of your self.  After a few more years, nobody understands but you want to keep it because it has become part of you.  Then it finally breaks after 20 years and you have to replace it and start all over again
Are you waiting for loneliness to paralyse? Are you waiting for sister midnight to anaesthetise?

Offline ronman

Re: valve / tube life span ??
« Reply #4 on: August 10, 2018, 10:12:51 PM »
Ok. Thanks.
So in a nutshell, buy quality tubes and all will be good.

(just dont whack them with a ladder  :giggle:)

Offline JonnyP

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Re: valve / tube life span ??
« Reply #5 on: August 10, 2018, 11:05:31 PM »
Most tubes have the lifespan, but dont hit them with a ladder
Are you waiting for loneliness to paralyse? Are you waiting for sister midnight to anaesthetise?

Online Ampdog

Re: valve / tube life span ??
« Reply #6 on: August 10, 2018, 11:43:57 PM »
Ronman,

Yes - and no.

Lamps for illumination are designed quite differently from electronic tubes/valves. In the latter the 'heating element' or heater (in early valves called a filament, looking rather like that in a lamp) needs to heat up to a quite lower temperature than in an incandescent lamp. For many reasons the real electron emitting element later became a narrow metal tube (cathode), heated by an insulated filament inside said tube. (That tube is coated with various rare earth elements to enhance its electron emitting function - but that is part of electron valve principles, not relevant here.)

While the filament of an incandescent lamp is heated to some 2,200C to give enough light (its only function), electronic valve cathodes normally operate at some 770C only (the heater/filament may be slightly higher.)  Typical colour is dull-red. Thus the life-time of an electron valve heater is (or should be!) orders higher than that of a lamp. Also, in a valve the heater does not fail so much because of shock, than the valve itself 'gives out' because of lowered emission of electrons, mainly because of failing of cathode coating material etc.  This effect is not linear with time but increases towards the end-of-life of the valve. (You may have read before that many of us who have experienced the hey-day of valves, hardly ever had a valve fail because of breakage of a heater. You may also imagine P.A. valve amplifiers being knocked about in a trailer travelling from venue to venue, heater still working afterwards - although then cold, of course.)

This is a very brief and general description of matters -  lots of other factors influence valve life, but this hopefully suffices to answer your question for now.     
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)

Offline capetownwatches

Re: valve / tube life span ??
« Reply #7 on: August 11, 2018, 09:15:06 AM »
If you intend to keep the Woo long term, make it a mission to source at least one backup pair of drivers and a quality NOS power tube.
For peace of mind more than anything else.
The good stuff is definitely getting harder to find for sane money.

That said, no one can say for sure how long a particular valve might last in your particular chain.
Enjoy the music and don't think about it until you need to think about it...  :groovy:


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Offline ronman

Re: valve / tube life span ??
« Reply #8 on: August 11, 2018, 09:29:55 AM »
Morning all

Some very insightful replies.
Nice input Ampdog.
Reading all this makes me grin again and inspires some shopping!!
Thanks Capetownwatches

Be well

Offline marantz123

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Re: valve / tube life span ??
« Reply #9 on: August 14, 2018, 08:51:04 AM »
Gotta say...a lightbulb in long term service in a storeroom would likely collect a nice layer of dust on its glass...and(its light intensity) would look dull compared to clean glass. Also....was it a 60w bulb that you replaced with a 100w bulb ?  :)

Offline El Sid

Re: valve / tube life span ??
« Reply #10 on: August 14, 2018, 11:54:37 AM »
As an aside, our understanding of light bulbs has been wrong all along - it turns out that they don't actually emit light, but rather suck dark in! See:  A New Theory of Light

I haven't given much thought to how this applies to valves, but some of my older valves do have a lot of residual darkess in them.

Offline Steerpike

Re: valve / tube life span ??
« Reply #11 on: August 14, 2018, 12:42:27 PM »
As an aside, our understanding of light bulbs has been wrong all along - it turns out that they don't actually emit light, but rather suck dark in!

Seven is the number of the young light - it forms when darkness is increased by one.

Offline Mars

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Re: valve / tube life span ??
« Reply #12 on: August 14, 2018, 04:53:53 PM »
Nice quote, Steerpike!

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Offline El Sid

Re: valve / tube life span ??
« Reply #13 on: August 14, 2018, 05:35:38 PM »
Well obviously Pink Floyd have the answer...

Offline ronman

Re: valve / tube life span ??
« Reply #14 on: August 15, 2018, 11:27:11 AM »
Valid point     but globes were from bulk box    and there was a regularly cleaned cover over the globe

Globes suck dark in!!!  I like that.

Thanks for the input guys