Valves life expectancy question.

[jibidy]

My Teacher tells me that Valves can actually last many years more than most people think, He says that he has had Valve preamps and poweramps for around ten years and never needed to replace the valves.

Kind of like guitar cables, the problem was in the manufacturing techniques when they were first around but the quality over the years (im guessing since about the 60's) has become much better to the point where you dont really have to worry about it to much.

I guess my question is this. Is the life expectancy of valves really as  short as 1-2 years or is this bit of an old wives tale that doesnt really matter these days?
Same with cables. Guitar cable and power cables.

I know speaker cables are different because speakers have such a low impedance.

[Twinfan]

It's all down to use.  You can't say life in years unless you know how often they're going to be used per week/month etc.

[AndyR]

I bought a Laney 50w master vol combo in 1983, played it non-stop at home for many years, did 150+ 2 hour gigs, and many many more 4 hour+ rehearsals...

I used to carry spare valves, fuses, whatever, but I never used them (and I gave the valves away eventually).

It's still got all the original valves in it, and when I tried it a few months back, it still does exactly what it used to do...

However, if I was about to start using it again in anger... I would get someone to service/overhaul it! :lol:

[jibidy]

I mean like everyday use. Quite heavy use.

Ive heard of people buying those old wem or watkins amps with the original valves and just keeping them in.

[MrBump]

Also depends on the bias adjustment.  They can be adjusted to run quite cold which extends their life, I think.

Might shag the OTs though...

[hunter]

like said before, it depends on usage.

You can burn them pretty quickly if you run your amp flat out e.g. with a power soak all the time.

Think of them like tires, you can drive slow and carefully or leave rubber on the street by doing wheelies each time you start.

Get good quality, matched tubes that are biased correctly, warm your amp up well and don't throw it around while tubes are still hot and you can have fun with 'em for long.

[jpfamps]

My large box of dead valves would suggest that they aren't indestructible......

It all really depends on usage.

Furthermore, the fact your teacher has had an amp for 10 years without changing the valves is an example of one, so is not statistically significant.

Pre-amp valves are generally run very conservatively and will work for ages. It is very rare to find a pre-amp valve that has expired, the exceptions being DC coupled cathode followers (eg Marshalls) and reverb drivers in Fender-style circuits.

Power valves can last a very long time too depending on how conservatively they are used/ biased.

e.g. EL84 based amps for example tend to run the valves very hot, often well over the maximum rating, and thus tend to suffer failure.

With use valves slowly deteriorate in performance over time, so installing a new set of valves will often improve the tone of your amp if you have haven't changed the valves for several years; however if you are happy with the sound of your amp I wouldn't bother changing the valves.

Incidentally running an amp flat out (either into an attenuator or a speaker) will cause the plate dissipation to reduce to zero, thus reducing the wear on the valves.

Power valve life is usually a function of the time the amp has been on and the extent of any mechanical disturbances.

[tomjackson]

I don't think the quality of valves has increased over time, generally I'd guess it was the other way round.
That said I think the current manufacturers have got a lot better and JJ seem pretty good.

As previously posted I've just got a WEM amp from about '73, the valves look like they might be original but even though they might be 35 years old I can't draw a conclusion because I have no idea how much they have been used or if they were nicked out of another amp.

Valves are a bit like light bulbs, they work until they don't......

[AndyR]

Valves are a bit like light bulbs, they work until they don't......

:lol: love it...

Furthermore, the fact your teacher has had an amp for 10 years without changing the valves is an example of one, so is not statistically significant.

I was thinking that actually. One of the reasons I posted my little story is that I've got one of those amps that lasted nearly 20 years of solid use without me ever changing anything in it. I didn't know any different, it's only since coming on here I've found myself wondering "bluddy hell, what was I thinking?!" ... but on the other hand, the damn thing worked, and in the later period of use (late 90s to 2001 or so) it was sounding even better! It's about the last piece of kit I'd part with, even though I don't use it now. The other guy with his Marshall kept getting re-valved etc and sounded sh1t in comparison - we, not knowing much, just thought he had a cr@p temperamental one and I had a nice reliable one... :lol:

Having said all that, given its age, and what it's been through (it could do with new pots, the knobs of various controls got busted off, they still work, but there's not enough spindle to put a knob on), I would definitely be getting it serviced and overhauled if I was about to use it to any extent - I'd be wanting all the valves checked/replaced, all these "cap" thingies looked at, etc... And it's not something I'm remotely interested in learning how to do myself - hats off to you guys who do it :D

[Elliot]

My experience with a Fender Blues Junior (which has had the bias cooled from the insane factory bias) which I have owned for 4 years and use everyday is that the 12AX7s/5751s pre-amp valves have not deteriorated at all (swap in, swap out - no difference) but the EL84 power valves - I have always used either matched pair Electro Harmonix or for the last 2 years matched pair New Sensor 'Mullard' reissues - are that the EL84s go too bassy after 1 year and have to be replaced.  In the late 80s I owned a Vox AC30 and the same thing happened with that. 

BTW in my experience lots of people who talk about speaker break-in (like, after 4 years the speaker is nicely broken in and has tons of bass) are actually talking about powervalve degredation - their speaker is not so 'broken in' after a re-tubing!

So pre-amp valves last ages, powervalves - at least EL84s - deteriorate quickly

[dave_mc]

older valves were better, surely? They've got worse since the 60s (certainly since the last US and british valve factories shut), not better. Unless everything I've heard and read about them is untrue. :)

[jpfamps]

Well the real hardcore valve hi-fi punters reckon that grid winding quality started to so south in the 50s (!!) once the use of negative feedback became prevalent, and hence amp distortion did not depend solely on valve quality.

Certainly by the late 80's early 90's valve quality was often fairly poor. Also many valves, eg KT66s, and most rectifiers went out of production.

There is now a good selection of current production valves and generally the quality is pretty decent (much better than late 80's).

I've had good results with modern valves in all styles/ages of amp.

[dave_mc]

thanks :)

[HTH AMPS]

I think in general there are some nice valves in current production, but there are also some tat too.  Also, the quality isn't very consistent - you seem to get batches of valves where the quality is shitee and they end up in circulation for years as no reputable valve reseller wants them, but some unlucky punter will eventually get them some way or another.

I still don't think there are any valves being made now that are as good as the equivalent from the 60s/70s/80s.  The 90s were a wasteland for current production - remember Marshall changing to those shitety 5881s because they couldn't source EL34s of sufficient quality ???

[Alex]

My Marshall still had Tesla valves (now JJ) in the power amp and worked fine. I did use it quite a lot (and excessively loud as well), they just held and there was no warning or problems.

In general, power valves will die eventually, preamp valves not unless something is broken. But you'd still want to replace preamp valves, because they deteriorate in sound quality.
The 1-2 years change advice of power tubes seems to be much too short for the majority of amateur players, I think it should be more around 4-5 years. However, I don't know if Class A amps not have a higher strain on power valves than class A/B.