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    Output tube rotation???

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    Kentley

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    Output tube rotation???

    Post by Kentley on Fri Feb 12, 2016 11:02 pm

    I got my little mind thinking about the uneven output tube temps in my ST-120. Since the rear tubes tend to run substantially hotter, is there perhaps a benefit to rotating the four KT-xxx periodically? Kinda like rotating tires on my '69 Chevy Nova.......???


    Last edited by Kentley on Fri Feb 12, 2016 11:03 pm; edited 1 time in total (Reason for editing : Wrong year on Chevrolet. Dementia...)

    MontanaWay

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    Re: Output tube rotation???

    Post by MontanaWay on Sat Feb 13, 2016 12:49 am

    I can't say for sure, but I don't think that rotating the tubes will extend the life of any of them. They all run quite hot, sure, the rear ones run a bit hotter than the front ones, but I have not ever heard, nor read, that rotating hotter running tubes with somewhat cooler running tubes will make any difference in the life of them.

    Kentley

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    Re: Output tube rotation???

    Post by Kentley on Sat Feb 13, 2016 6:03 am

    MontanaWay wrote:I can't say for sure, but I don't think that rotating the tubes will extend the life of any of them. They all run quite hot, sure, the rear ones run a bit hotter than the front ones, but I have not ever heard, nor read, that rotating hotter running tubes with somewhat cooler running tubes will make any difference in the life of them.

    I guess it would be pretty difficult to  prove, at any rate. On the other hand, since it's a given that socket and pin maintenance should be performed regularly, as well as bias fine-tuning, I guess I'll give rotation a shot. Can't hurt {famous last words}.
    Thanks, Mr. Way. Cool

    peterh

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    Re: Output tube rotation???

    Post by peterh on Sat Feb 13, 2016 9:40 am

    Kentley wrote:I got my little mind thinking about the uneven output tube temps in my ST-120. Since the rear tubes tend to run substantially hotter, is there perhaps a benefit to rotating the four KT-xxx periodically? Kinda like rotating tires on my '69 Chevy Nova.......???
    Each time a tube is pulled there is a small risk of damage, both by mechanical stress
    on the tube and socket, but also due to the risk of shaking loose debris inside the tube.
    There is also the stress that might occur when re-bias, especially if it happens to
    start with a larger the normal current.

    I'd suggest letting good tubes be left alone ( and bad tubes thrown away )

    Kentley

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    Re: Output tube rotation???

    Post by Kentley on Sat Feb 13, 2016 9:53 am

    Points well-taken, Peter. BUT - logically, if a tube's bias has drifted to the high side, wouldn't it make sense to correct it ASAP instead of leaving it too high? Or is this nornally a sign that the tube is on its way out, in which case you should plan for replacement soon?

    peterh

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    Re: Output tube rotation???

    Post by peterh on Sat Feb 13, 2016 11:24 am

    Kentley wrote:Points well-taken, Peter. BUT - logically, if a tube's bias has drifted to the high side, wouldn't it make sense to correct it ASAP instead of leaving it too high? Or is this nornally a sign that the tube is on its way out, in which case you should plan for replacement soon?
    Of course a tube that has drifted ( > 10%) should be corrected asap.
    But continous repeated drifting is a sign of a tube on it's way to the wastebasket ...

    Usually tubes will drift somewhat during the first hours of use, but after 10h or so
    they will remain constant, until it slowly begins to drop. But the drop will typically
    be 1000 or so hours away.

    Tubes4ever

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    Re: Output tube rotation???

    Post by Tubes4ever on Sat Feb 13, 2016 3:05 pm

    Peterh is correct. Tubes shouldn't drift UPWARD in current as they age.
    Leaving tubes alone in their sockets is the best advice. Tube sockets don't need regular maintenance unless you are tube rolling.

    Kentley

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    Re: Output tube rotation???

    Post by Kentley on Sat Feb 13, 2016 3:14 pm

    That settles it. Thanks, gents.

    audiobill

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    Re: Output tube rotation???

    Post by audiobill on Sat Feb 13, 2016 6:02 pm

    Just my 2 cents, I've observed that frequent tube "rollers" seem to have the most trouble with their amps.

    Perhaps a coincidence........

    peterh

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    Re: Output tube rotation???

    Post by peterh on Sat Feb 13, 2016 6:04 pm

    audiobill wrote:Just my 2 cents, I've observed that frequent tube "rollers" seem to have the most trouble with their amps.

    Perhaps a coincidence........

    I don't know. My 6550 have been in their sockets for > 2000h now .
    They are JJ by the way.

    MontanaWay

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    Re: Output tube rotation???

    Post by MontanaWay on Sat Feb 13, 2016 6:08 pm

    audiobill wrote:Just my 2 cents, I've observed that frequent tube "rollers" seem to have the most trouble with their amps.

    Perhaps a coincidence........

    I totally agree......leave them alone!...in most cases of tube rolling, we 'want' to hear a difference, when in fact there is very little difference in the audible sound.
    If it sounds great and all is good..leave them!!!

    deepee99

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    Re: Output tube rotation???

    Post by deepee99 on Sat Feb 13, 2016 6:36 pm

    MontanaWay wrote:
    audiobill wrote:Just my 2 cents, I've observed that frequent tube "rollers" seem to have the most trouble with their amps.

    Perhaps a coincidence........

    I totally agree......leave them alone!...in most cases of tube rolling, we 'want' to hear a difference, when in fact there is very little difference in the audible sound.
    If it sounds great and all is good..leave them!!!

    That would be my hard-earned experience as well. Also, may I be so bold as to suggest that output tube-rolling is quite unproductive. A little rolling in the drivers and preamp is far more useful to find that flavour that suits one best. Output tubes, not near as much if at all.

    MontanaWay

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    Re: Output tube rotation???

    Post by MontanaWay on Sat Feb 13, 2016 6:42 pm

    deepee99 wrote:
    MontanaWay wrote:
    audiobill wrote:Just my 2 cents, I've observed that frequent tube "rollers" seem to have the most trouble with their amps.

    Perhaps a coincidence........

    I totally agree......leave them alone!...in most cases of tube rolling, we 'want' to hear a difference, when in fact there is very little difference in the audible sound.
    If it sounds great and all is good..leave them!!!

    That would be my hard-earned experience as well. Also, may I be so bold as to suggest that output tube-rolling is quite unproductive. A little rolling in the drivers and preamp is far more useful to find that flavour that suits one best. Output tubes, not near as much if at all.

    yes, that is very true. Drive/preamp tube rolling can make quite a difference in the overall sound.
    But again, once you find 'your sound'......leave it be and just enjoy tube music! Very Happy

    Kentley

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    Re: Output tube rotation???

    Post by Kentley on Sat Feb 13, 2016 11:46 pm

    This has been a fine example of getting more than I bargained for, and it's a good thing.
    The truth is that I've had only two sets of output tubes in my ST-120 in a year, and I've had zero problems with either set. No red-plating: no bias drift. I suspect my concerns came from the "wisdom" that tube amps are inherently "high-maintenance" and that there must be something to futz with at all times.
    So - especially with the high-voltage areas of my weaponry - IF IT AIN'T BROKE, DON'T BREAK IT.

    deepee99

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    Re: Output tube rotation???

    Post by deepee99 on Sun Feb 14, 2016 12:47 pm

    Kentley wrote:This has been a fine example of getting more than I bargained for, and it's a good thing.
    The truth is that I've had only two sets of output tubes in my ST-120 in a year, and I've had zero problems with either set. No red-plating: no bias drift. I suspect my concerns came from the "wisdom" that tube amps are inherently "high-maintenance" and that there must be something to futz with at all times.
    So - especially with the high-voltage areas of my weaponry - IF IT AIN'T BROKE, DON'T BREAK IT.

    It's a truism that while tubes are physically more delicate than sand components, tubes are far more robust electrically. This is not to tempt you away from the sound advice of others here to leave well enough alone . . . Everytime you "roll" a tube, esp. the top-heavy outputs, some degree of damage is going to be inflicted on the pins and sockets. HRH Latino suggests a monthly bias check, bearing in mind that voltages will vary slightly depending on what voltage is coming out of the wall.

    tubenutr

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    http://dynacotubeaudio.forumotion.com/t2949-output-tube-rotation

    Post by tubenutr on Wed Feb 24, 2016 8:24 pm

    Rotate baby, rotate lol!

    Kentley

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    Re: Output tube rotation???

    Post by Kentley on Wed Feb 24, 2016 10:41 pm

    Eskimo wrote:Rotate baby, rotate lol!
    Perhaps the wisest course of action would be to take a page from your friendly M.D.'s "handbook" and periodically request each output tube to "Turn your plates and cough, please". What a Face
    {Latex gloves, of course.}

    tubenutr

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    Re: Output tube rotation???

    Post by tubenutr on Wed Feb 24, 2016 11:07 pm

    Ze little gray cells are rejuvenated by ze cold.

    Mon, ami.

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