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PostPosted: Thu Jul 26, 2018 6:47 am 
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I'd like to compile data on the above subject putting together a quick reference chart. A thread that new members might want to refer to when investigating tube gear.

I'm asking the collective whom which have been long time users of vacuum tube gear to contribute.

What is the average life expectancy of common vacuum tubes? Is it dependent on the size of the tube or type of tube?

For consistency add info on a per hours basis. Preamp/Power/rectifier categories.

If you don't have anything of value to add to this thread don't contribute.

Audiois1st

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PostPosted: Thu Jul 26, 2018 6:56 am 
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Audiois1st wrote:
What is the average life expectancy of common vacuum tubes? Is it dependent on the size of the tube or type of tube?
t


Tube life expectancy is dependent on material construction and how the tube is employed i.e. circuit type, operating parameters, thermal cycles, etc.


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PostPosted: Thu Jul 26, 2018 7:09 am 
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None of it would be relevant or valid.

Not a reliable list....

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PostPosted: Thu Jul 26, 2018 7:12 am 
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Simply too many factors so case by case basis is the only thing possible.

Some people re-tube just for the halibut.


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PostPosted: Thu Jul 26, 2018 7:45 am 
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Audiois1st wrote:
I'd like to compile data on the above subject putting together a quick reference chart. A thread that new members might want to refer to when investigating tube gear.

I'm asking the collective whom which have been long time users of vacuum tube gear to contribute.

What is the average life expectancy of common vacuum tubes? Is it dependent on the size of the tube or type of tube?

For consistency add info on a per hours basis. Preamp/Power/rectifier categories.

If you don't have anything of value to add to this thread don't contribute.

Audiois1st

A worthy goal :idea:

Start here http://www.tubebooks.org/ and scan the old school technical data books from high volume tube manufacturers like RCA, Western Electric, GE and Tung-Sol.
All audio equipment design engineers, during the decades when hollow state was king, would be very familiar with these books, or the European equivalents.

This is a great reference that directly looks at your concerns:
Reliability Factors for Ground Electronic Equipment, Keith Henny, 1956, 266 pages 8)
Discusses reliability factors in military electronics in the 50's.

Chapter 8 on "Components" has 63 pages, of which 61 pages are focused on the reliability of vacuum tubes.
Everything here should be noted as referencing Mil-Spec tubes, not your every day consumer parts.
Clear that many things influenced the useful life of a tube, even with experts designing equipment.

How to extrapolate this collection of knowledge to more recent tubes manufactured in much lower volume (maybe 99.99% less) is the challenge :?:


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PostPosted: Thu Jul 26, 2018 10:01 am 
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brf wrote:
Audiois1st wrote:
What is the average life expectancy of common vacuum tubes? Is it dependent on the size of the tube or type of tube?
t


Tube life expectancy is dependent on material construction and how the tube is employed i.e. circuit type, operating parameters, thermal cycles, etc.


You nailed it brf! I have seen the same brand and model tubes rated to last as little as 5k hours in one type and brand of gear and as long as 100k hours in another (6DJ8 btw). I have also seen KT-88 power tubes rated to last for as little as 1k hours in one model of amp and as long as 10k hours in another. It really dépends on how hot/hard/agressive the design of the gear in question was speced for.


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PostPosted: Thu Jul 26, 2018 11:05 am 
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Okay work with me guys. Even if we put a range per tube type in hours to show operating range conservative to aggressive. I realize there are variables but it's to give an idea of average life expectancy.

Anyone with the knowledge willing to submit some figures? Or provide a link to a site that may have already compiled this information but I wasn't able to find.

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PostPosted: Thu Jul 26, 2018 11:23 am 
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You are better off using Google and look up the equipment in question to see what tube is recommended etc.

As an example, if you look up Audible Illusion Modulus tube recommendations you will find that they were notoriously hard on tubes, therefore, the life expectancy of a 6922 tube in that pre would vary significantly when compared to another 6922 based pre.

Also, a tube may no longer be suitable for a sensitive gain/driver stage but will work just fine as a cathode follower.

Rectifier tube = they will last a lifetime
Small signal tubes = <5,000 hrs
Power tubes = 1,000 - 1,500 hrs


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PostPosted: Thu Jul 26, 2018 1:29 pm 
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My experience with a Rogue Audio power amp and Audio Research pre over the last 14 years after collecting and trying many many different tubes:
New production Russian made power tubes (EH KT88, Gold Lion KT88 and KT66)— 1500 hours to 2500 hours of use before the sound noticeable degrades.
New production Chinese made power tubes (PentaLabs KT88SC, Treasure KT88 and KT66, Treasure KT120, Psvane greyglass KT88, Shugang EL34B)—— 70% last 1000 to 2500 hours, the other 30% last 1 day to 3 months. Quality control seems to be very sketchy, even if you buy from a good dealer that really tests and matches them. So if you want to use a quad of these in your amp, better buy 6 or 8 so you have spares for the inevitable failures. They do sound nice though when they work.
NOS or used tested new vintage power tubes (Mullard EL34, GEC KT66, EI KT90, 6n3cE, RCA and G.E. 6L6GC)— 2500 hours to 5000 hours or more. They do test slightly weaker over time but have yet to hear any sound degradation on them after thousands of hours. Never had one fail on me either.
New production small signal tubes—- 1 month to thousands of hours. In my experience, NP 12ax7s, and 6dj8/6922 don’t loose strength, they just get noisy either quickly, or slowly over time. A bit of a crapshoot but at least they are cheaper than the power tubes.
NOS small signal tube (Teles, Mullard, Amperex, Siemens, RCA, GE, Sylvania etc from 1950s and 1960s)——5000 hours to 50,000 hours or more depending on the circuit—they will probably outlast you! Have never had one go bad or noisy in my gear.
My amp is not tube rectified so can’t comment on those.
Just one mans experience, enjoy the roll!


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PostPosted: Thu Jul 26, 2018 1:37 pm 
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And at what bias point?

Just like a clutch in a car....can last for decades or a day.

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PostPosted: Thu Jul 26, 2018 2:31 pm 
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If you need help in the database development I have extensive experience in Excel, Access, and MySql.

I think you are in an uphill battle. The number of variables that would need to be put on each tube
would make the data irrelevant.

If you have a range of 1,000 hrs to 10,000 hours you will be no further ahead than checking the specific
tube and manufacture specs.

Most here change the tubes when they think they hear sound deterioration, and that is something you cannot
put in a database.

Something like these,
How long is a piece of string?
What is green for?
How long will a car last?
When will the Leafs win a cup?
Audio related, How long will my cartridge last? etc.

Regards
Ohms

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PostPosted: Fri Jul 27, 2018 9:06 am 
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MENDEL24 wrote:
My experience with a Rogue Audio power amp and Audio Research pre over the last 14 years after collecting and trying many many different tubes:
New production Russian made power tubes (EH KT88, Gold Lion KT88 and KT66)— 1500 hours to 2500 hours of use before the sound noticeable degrades.
New production Chinese made power tubes (PentaLabs KT88SC, Treasure KT88 and KT66, Treasure KT120, Psvane greyglass KT88, Shugang EL34B)—— 70% last 1000 to 2500 hours, the other 30% last 1 day to 3 months. Quality control seems to be very sketchy, even if you buy from a good dealer that really tests and matches them. So if you want to use a quad of these in your amp, better buy 6 or 8 so you have spares for the inevitable failures. They do sound nice though when they work.
NOS or used tested new vintage power tubes (Mullard EL34, GEC KT66, EI KT90, 6n3cE, RCA and G.E. 6L6GC)— 2500 hours to 5000 hours or more. They do test slightly weaker over time but have yet to hear any sound degradation on them after thousands of hours. Never had one fail on me either.
New production small signal tubes—- 1 month to thousands of hours. In my experience, NP 12ax7s, and 6dj8/6922 don’t loose strength, they just get noisy either quickly, or slowly over time. A bit of a crapshoot but at least they are cheaper than the power tubes.
NOS small signal tube (Teles, Mullard, Amperex, Siemens, RCA, GE, Sylvania etc from 1950s and 1960s)——5000 hours to 50,000 hours or more depending on the circuit—they will probably outlast you! Have never had one go bad or noisy in my gear.
My amp is not tube rectified so can’t comment on those.
Just one mans experience, enjoy the roll!

An excellent first hand account dating back 14 years. Thank you. I've only had tube gear for the last 2.5 years. Does anyone else have anything of value to add as MENDEL24 has? I didn't realize the variance you experienced existed. Others must have more information to provide on this topic.

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PostPosted: Fri Jul 27, 2018 9:33 am 
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Another variance could be KT-120 tube life on amps designed for KT88/6550 tubes, comparing to using them on amps designed from the ground up to use KT120s.


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PostPosted: Fri Jul 27, 2018 10:11 am 
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It's all over the map. It tends to come down to the utilization in a given circuit.

Therefore, tube lifespan information is generally applicable to a specific piece of gear, as an average, in that circuit and in that socket.

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PostPosted: Mon Jul 30, 2018 6:23 am 
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I agree that there are too many variables to provide a comprehensive list on the life of different tubes, but a sharing of experiences with certain tubes in certain gear can be helpful to those using tube electronics, especially those just starting out. Especially given the costs of tubes these days.
Tube rolling is a lot of fun but it is nice to have an idea of where to start.


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