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    Tube Longevity

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    n3ikq

    Posts : 26
    Join date : 2014-10-16

    Tube Longevity

    Post by n3ikq on Mon Dec 29, 2014 1:08 pm

    Hi, under NOMINAL conditions (1.56v bias, 117v power) approximately how many hours will a typical output tube last in an ST70? Does playing at high volumes reduce tube life more so then just on but idling? I assume a tube fails when it "runs out" of electrons on its cathode or its filament burns out so it's probably not good to leave the amp on if it is not being used. Thanks!

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Tube Longevity

    Post by sKiZo on Mon Dec 29, 2014 6:05 pm

    General consensus is the average power tube should be good for around 3000 hours, all else for 10,000 hours. As you mentioned, how hard you drive them can make a big difference. That was part of why I went with the KT120's in my ST120 - I figure they should last forever in a KT88 based amp.

    (Not an option in the ST70 btw ... not enough iron to keep them happy)

    I turn mine off if it's gonna be a couple or three hours between sessions or when I leave the house.


    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Tube Longevity

    Post by deepee99 on Wed Dec 31, 2014 12:35 pm

    sKiZo wrote:General consensus is the average power tube should be good for around 3000 hours, all else for 10,000 hours. As you mentioned, how hard you drive them can make a big difference. That was part of why I went with the KT120's in my ST120 - I figure they should last forever in a KT88 based amp.

    (Not an option in the ST70 btw ... not enough iron to keep them happy)

    I turn mine off if it's gonna be a couple or three hours between sessions or when I leave the house.


    I've resolved bit of the tube-ageing issue by installing some Bedini sand amps when I just want background music to listen to while I'm working, to save wear and tear on the tube rack. (Am also running Tung-Sol KT-120s).
    Bias setting also has an influence on tube life. If you can live with say, .5 or .55 per tube, your tubes will live longer, or so I'm told. Andy Bowman suggests as low as .45 as a starting point for KT-88/6550 tubes.

    Bob L, Roy, you guys might answer this one: does running in triode mode have any salutary effect on tube life?

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Tube Longevity

    Post by sKiZo on Wed Dec 31, 2014 2:36 pm

    Way I understand it, a tube in triode mode runs just as hard, if not harder, as a pentode configuration. Difference in output is due to how the signal is routed through the tube.

    And ya ... stands to reason that a lower bias setting will go easier on the tube, but there's always a trade off. I prefer the PUNCH of a higher bias. Especially true with the KT120's as those really sing at 60mV ... maybe more so in a KT88 based amp. Much of the "sound" is due to how the tubes interact with the rest of the components in an amp, and my target is the "sweet spot". Given that, or improved longevity ... hey, you only live twice ... ;-}

    PS ... I seldom "listen" to music. For me, it's more LISTENing when I have the time to sit back and sink in. Full immersion, doncha know ... blub blub ...

    corndog71

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    Join date : 2013-03-19
    Location : It can get windy here

    Re: Tube Longevity

    Post by corndog71 on Wed Dec 31, 2014 3:17 pm

    According to an old Sylvania engineer, tubes should last roughly 10,000 hours. Power tubes can achieve this by running at half of max dissipation. Now there's a puzzle for you to solve.

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Tube Longevity

    Post by deepee99 on Wed Dec 31, 2014 3:31 pm

    corndog71 wrote:According to an old Sylvania engineer, tubes should last roughly 10,000 hours.  Power tubes can achieve this by running at half of max dissipation.  Now there's a puzzle for you to solve.

    There's plenty of anecdotal evidence that the 1960s-vintage production tubes lasted that long. Guess the modern solution would be an M-125 running eight KT-120s. Wink

    And sKiZo, I'm kinda with you. Life is short, tubes are cheap. I run mine at .6.

    Gregg R.

    Posts : 80
    Join date : 2014-02-20
    Age : 71
    Location : Land of 11,842 Lakes

    Tube Longevity

    Post by Gregg R. on Wed Dec 31, 2014 8:08 pm

    I run my Shuguang EL34s a little high at .425v; they sound more dynamic that way. At less than $40/quad, I'm not too worried about tube life. Heck, at 70 years old, I'm more worried about Gregg's longevity!!

    Have a Happy New Year!!

    n3ikq

    Posts : 26
    Join date : 2014-10-16

    Re: Tube Longevity

    Post by n3ikq on Mon Jan 05, 2015 9:29 am

    Good Point! Life is short, turn it up!

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Tube Longevity

    Post by deepee99 on Tue Jan 06, 2015 12:10 pm

    n3ikq wrote:Good Point! Life is short, turn it up!
    November 3 and sKiZo, I'm with you guys. We can always get new neighbours.

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Tube Longevity

    Post by sKiZo on Tue Jan 06, 2015 4:02 pm

    I went through a lot of neighbors until the deaf guy bought the house next door.

    He still goes on about the "ghost trains" rumbling by and shaking the house at odd times of the day and night. I'll see him through the window, out in the yard and looking up and down the abandoned track bed trying to spot one when I'm cranking it ...

    audiobill

    Posts : 271
    Join date : 2014-03-13
    Location : Philadelphia

    Re: Tube Longevity

    Post by audiobill on Tue Jan 06, 2015 5:05 pm

    Get him a "bass shaker" for his easy chair......

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Tube Longevity

    Post by deepee99 on Tue Jan 06, 2015 5:43 pm

    Bone conduction. We need bone conduction . . .

    Bob Latino
    Admin

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    Join date : 2008-11-26
    Location : Massachusetts

    Re: Tube Longevity

    Post by Bob Latino on Tue Jan 06, 2015 6:16 pm

    Major thread drift you guys .. lol ..

    Back to tube longevity ...

    Years ago when all the tubes were made in the USA, Great Britain and Germany and quality control was better, tubes would last a long time. They used better alloys in the contruction of the metal parts inside the tube. They held better tolerances on distances between the anode, cathode and screen placement. Tubes did last noticeably longer. Today all the tubes are made in Russia, China or the Slovak Republic. They try to MAKE the tubes as cheaply as they can. Quality control is not as good .. The glass on some octal tubes is crooked on the base, the tube pins are undersized etc. Output tubes today should last 2000 to 3000 hours. Driver tubes 5000+ hours ... If you get more than a year out of a rectifier tube today, you are doing good. This is the reason why NOS or lightly used USA made tubes (RCA, Sylvania, GE etc.) go for big bucks on Ebay .. Audiophiles know that those tubes are better and they drive the prices up. If you want to listen to tube audio gear, this is an issue we all have to deal with ...

    Bob

    deepee99

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    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Tube Longevity

    Post by deepee99 on Tue Jan 06, 2015 6:24 pm

    Yeah, what Bob said. Pass that thang over to me so no more drifting.

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Tube Longevity

    Post by sKiZo on Wed Jan 07, 2015 12:41 am

    audiobill wrote:Get him a "bass shaker" for his easy chair......

    Speak of the devil ... Looky what I did to my easy chair just last week ...




    Driving them with a 200wpc mono plate amp ...

    Trrrrrrrryyyyyyyyy iiiiiiiiiittttttttttt
    yyyyyyyyouuuuuuuuuuuuullllll llllllllliiiiiikkkkkkkkeeee iiiiiitttttttttt!!!!!!!!!!!

    EDIT > > Just caught the admonishment about thread drift ... er ... uh ... these will definitely shorten tube life unless you isolate the amp. I use Vibrapods -



    Stacked #4 and #1 under the back corners where all the weight is, and single #1's on the front corners. Zero vibration transmitted from the room. Highly recommended!

    There ... back on track ... sort of ...  geek

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Attempting to drift back to the centre-line

    Post by deepee99 on Wed Jan 07, 2015 11:10 am

    SkIzo, I am really tempted to try one of those b*tt-shaker layups, just 200 more watts not on the financial table right now.
    There was an article maybe 30 years ago in Stereo Review (or was it Mad Magazine) about direct bone-conduction bass, written tongue in cheek, before the era of megawatt amplifiers or the invention of powered or even passive subwoofers. Can't remember where the needles went.
    If an OCD tube-roller, be aware of pin dimensions, as Bob L. just mentioned. They DO vary. Antique Tung-Sol 6550s have smaller pins than their new Russian KT-88/120 counterparts. If you've been using Russkies and then try out a set of original 6550s, you'll find much to your discomfort that the Russian pins have blown out the pin-holders a tiny bit, to where the old tube will not make contact at certain, important places like Pin 7. It's a pretty light show when that happens as your beautiful antique 6550 red-plates and emits magic smoke, but it's not worth the hundred bucks.
    Quick fix: tighten up the sockets with an optical screw-driver, pour a bucket of D-eoxit over the mess, squirrel in pipe cleaners to muck 'em out, and wipe the tube pins with some bronze wool. Repeat.

    My hard-earned advice: suck it up and buy the best New Jersey or Dutch tubes you can, especially for drivers and preamps. Second-best advice: the Russian Tung-Sol KT-120s from Jim McShane are pretty tough to beat and you can drive the shite out of them. If they go to the grave at 3k hours, that's in the real world probably three to four years. Not a bad thing; they'll make more unless we go to war. Consider them meantime as consumables, like hamburger.

    Last thing, has anybody seen MontanaWay's (Holger's) new Big Bopper M-125s on tube nirvana? Individual per-tube bias, and a board that replaces the multi-cap with individual caps, all mil-spec PCBs below decks. Holger works in concert with Roy and Bob so all is kosher.



    peterh

    Posts : 641
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Tube Longevity

    Post by peterh on Wed Jan 07, 2015 12:23 pm

    I have a quad of JJ-6550 in an vta-70 that has been active since june 2013.
    Since november 2014 they have accumulated 160h so my guess is that they have done >2000h
    Still no bias drift and no flashes.

    audiobill

    Posts : 271
    Join date : 2014-03-13
    Location : Philadelphia

    Re: Tube Longevity

    Post by audiobill on Wed Jan 07, 2015 4:27 pm

    Bass shakers - constipation cure!

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Tube Longevity

    Post by sKiZo on Wed Jan 07, 2015 6:52 pm

    More on topic, more or less.

    I did pick up an hour meter for the ST120.



    Truth be told, I really can't say how many hours I've accumulated, and that should take the guesswork out of it. This one has non-volatile memory, so it doesn't lose the hours. Plenty of places I could pull DC from the chassis, but ... I've been planning to install a 24v power supply to do some lighting, and that's yet another reason to git er done.

    Rectangle LCD hour meter quartz 9-80 VDC, hourmeter




    ATTENTION: THREAD DERAIL AHEAD!
    FEEL FREE TO IGNORE THE FOLLOWING

    bASS shakers are something I was looking into for a while now. The ST120 paired with the Big Mac speakers can certainly get the rumble going, but these are pretty amazing. Yet another level of immersion. I did get a bit carried away with the amp ... 100watts should be more than enough to drive a pair hooked up in series to deliver a four ohm load to the plate amp. As is, I can only turn them up about a quarter of the way before I endanger the foundation here. Have to play around with attenuating the line level to see if that helps.

    And bone conduction ... I still got my bone fones ... anyone remember those?



    Just toss them around your neck and adjust the transducers to hit your collar bones, and instant stereo. Pretty slick - I still use them when mowing the lawn.

    anbitet66

    Posts : 131
    Join date : 2009-12-23
    Location : Valley Stream, NY

    Re: Tube Longevity

    Post by anbitet66 on Thu Jan 08, 2015 2:38 pm

    Skizo,

    Holy Good Night (as my Dad would say), I tried as I might, I couldn't ignore your post.  I nearly fell off the "throne" at the sight of your post at 5 AM. Sleep

    I was all of 14 when they debued, and I read about them in Radio Electronics (or an equivalent electronics magazine) waaaaaaaaaaaaaaaaaaaay back in '80.

    http://blog.modernmechanix.com/bone-fone/

    And that was the exact ad for them I remember.  They were around $80 with different colored sleeves weren't they?  I could not afford that, so I got a JC Penneys AM/FM stereo radio with 'phones for Christmas that year that cost maybe $25.  I always wanted to know if they really worked, or was this advertising fluff???

    Never thought to look to see if they are at "that auction site" but wouldn't be surprised to see some for sale.  So, do they sound as good as the ad says?

    Tony

    BTW, thanks for making me feel old.  No, wait, I already did.  Forget I brought it up.

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Tube Longevity

    Post by sKiZo on Thu Jan 08, 2015 3:01 pm

    $80 was a lot of money back then. Gas was what ... 70¢ a gallon?

    Luck with finding them on da bay, eh. Not sure if they didn't last, or they didn't make many, or just that folk who have them tend to hold on. Mine have held up well over the years, but I don't treat them rough either. You gotta wear the strap to get good conduction, or a sweatshirt works fine to keep the transducers tight to da bone ... good sound, and I get good reception out here in the sticks too ...

    Oh ... tube longevity. The blue tube that covers the radio has held up well as well ...  clown

    jsfrench46

    Posts : 1
    Join date : 2015-02-15

    Variac to the rescue!

    Post by jsfrench46 on Tue Feb 17, 2015 11:18 pm

    I'm sure this horse is almost dead, due to the repeated beatings----However....   I own and use a rebuilt (by me)ST-70, a PAS-3x, FM-3, Scott 299(a), 3 Heath A-9(C)'s, 2 Heath AA=121's, 1 Heath SA-2, 1 Magnavox AA-175, 2 Baldwin 54A's, and even a Silvertone Console Amp (PP-EL-84 X 4).  Also own a Jolida BRC-302, since I had to have remote in one of 'em.    In 12 years of engaging this addiction, I have only burned up a few power tubes-- (EL-34's in the Heath Amps).  This is attributed to two things: 1)  I always put in a CL-90 (or whatever appropriate for the device) Inrush Current Limiter in the Primary Circuit, and 2).  Never go beyond 115 VAC.  By necessity, this requires a Variac during all listening.  I have found no adverse effects from using this method, other than a slight increase in hum.  My K-Horns hum with everything, though--so it's really no big deal.  I'm sure there is a downside to this method, but it has worked for my equipment.  I don't want to ruin the vintage tubes/transformers I have, and this is the only way I have found to preserve them.  On occasion, I do crank some of these amps with KEF Reference 107/2's---These are 4-Ohm (more like 1 ohm at some frequencies) Power Suckers.  This, just in case some might think my amps are never "stressed."
    Can't wait for some of you to weigh in on this one!
    bounce  bounce  bounce  sunny

    zx

    Posts : 194
    Join date : 2011-08-05

    Re: Tube Longevity

    Post by zx on Wed Feb 18, 2015 5:43 am

    Varaics...I have 8ea here today....get them at yard sales...fleas....$10-15 at most.
    Never lose tubes... having  tubes for over 40years....just don't kill tubes!.. an all my Vintage tube amps an pramps Never sounded better with the AC set at 110-15....I sale a tube amps from time too time....thay get a Varaic with the Sale!..........
    I got tube here that are over 50 years old.....test 80-90%.....with the price of tubes...  think others would get this ezey fix....but there just post after post about tube death on all sites ....

    An how about the sound of the old hhscott....299c..355 pretuner puts my Krell KBL&KSL to shame...hehe ... some of the best tube sound I have ever had...
    An scott run some of there input  tube heater at 5.70.....
    But never used any cl-90s....but I sound like a plane...
    Thanks for any an all info on tubes............



    Thanks for the site Bob.......

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