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Tubes and TTs: Turn em off or keep em on?

Discussion in 'General Audio Discussion' started by BassKulcha, Nov 6, 2018.

  1. BassKulcha

    BassKulcha Cathode Follower Subscriber

    Messages:
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    Location:
    NYC
    Sometimes you need to leave the room for 5-10-15-20 minutes. Is is better to turn the tube amp OFF (in this case a Dynaco ST-70) to save tube life, or keep it ON to minimize inrush current/start-up tube stress?

    While I'm here, what about the AR-XA turntable I've been running lately? Better to NOT stop and start it when flipping/changing records, to minimize belt stretching? (I don't have the same concern with the TD-124)

    Or maybe the concern isn't really warranted? FWIW, I'm inclined to just keep em ON...
     

     

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  2. rebellovw

    rebellovw Super Member

    Messages:
    3,016
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    I turn it off if I'm going to be gone for a while - like hour or so - but just in and out - I leave on (Tube Monoblocks.)

    It doesn't hurt to turn them off - just don't do a quick off then on (immediate flicker of power switch) - as that puts a strain on the tubes.

    Mostly I turn on - use - several hours - then turn off.

    As far as turntable - I have a VPI Classic - always switch off - switch record - tight clamp - which rotates platter - and turn on.
     
  3. robert_kc

    robert_kc AK Subscriber Subscriber

    Messages:
    862
    Location:
    Midwest USA
    I own 24 vintage tube amps, all professionally restored. Recently an amp that had been restored by one of the top techs in the country suddenly put on a "spark show" (i.e., sparks shooting out of the top of the amp). Fortunately I was sitting a few feet away and was able to quickly unplug the amp. The amp has subsequently been repaired. (A wire wound resistor failed.) Moral to the story: Don't walk away from a vintage tube amp for more than a few minutes.
     
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  4. Mellotronix

    Mellotronix Active Member

    Messages:
    396
    I own a bunch of tube gear including 15 guitar amps--some vintage, some new, some heads, some combos etc. Only had one instance where something bad happened and it was a cracked vacuum tube that started a small fire in what was left of the bottle after it exploded. Of course, this happened at church during the sermon, but whatever. It was the most excitement that place had seen in years. People started whispering, "Dude, your amp's on fire..."

    Standby is your best friend, but I don't think your Dynaco has that feature. So, what can go wrong in five minutes? Probably nothing if you keep it in tip top shape and bias your tubes correctly. As long as you inspect it thoroughly every few weeks, it should be fine, and your tubes will thank you for not powering it down. The power that surges to the tubes on startup without a standby switch will wear them out faster than leaving them on for short periods between records. Your Dynaco probably has a slow startup system where it automatically delays sending the full current to the power tubes. But better check me on this.
     
  5. Route 66

    Route 66 AK Subscriber Subscriber

    Messages:
    703
    Location:
    Burbank
    I turn off my tubed equipment and turn it on an hour prior to a listening session. I leave my SS gear on all the time.
     
  6. AdamAnt316

    AdamAnt316 Collector of heavy things Subscriber

    Messages:
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    Location:
    MA
    I don't turn my tube gear on until I'm ready to listen to it. In the past year, I've learned to be careful with leaving my tube equipment on, as the output tubes in my Dynaco ST-70 have red-plated on me a couple of times. :eek: Both times, I was sitting in front of it, and was able to kill the power before anything majorly bad happened. All capacitors have been replaced except for the filter can and the micas, so this stuff can happen even if an amp has been "restored".

    As far as turntables go, I don't think there's anything wrong with leaving them plugged in all the time, though I don't leave them spinning in between listening sessions. Best to avoid wear on those ever-so-important motors and bearings. As for the platter, I always stop it before removing the record, in order to reduce the chances of accidents.
    -Adam
     
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  7. JoeESP9

    JoeESP9 ESL's & tubes since 83

    Messages:
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    Tube power amps that have a rectifier tube instead of a SS bridge rectifier have an automatic slow start because of the rectifier tube.
     
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  8. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    36,756
    Location:
    Southern NJ
    Sometimes yes, depends on the rectifier. Direct heat ones ramp up faster than the output tubes so there is a nice voltage spike.

    I don't turn my stuff on and off every time I leave the room, but if I'm not going to be back for a while it shuts off. "a while" is probably 30+ minutes. I have accidentally left things on for days.

    When I'm running the Thorens I don't usually stop it between records but when I'm done it gets turned off.
     
  9. BassKulcha

    BassKulcha Cathode Follower Subscriber

    Messages:
    1,103
    Location:
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    Thanks for the input folks.

    Is it safe to say that the possible catastrophic issues from leaving the amp ON trump the probable tube wear from inrush current?

    Second thing is that, while the ST-70 was (partially) restored about a year ago, I still don’t know how to properly bias the tubes, so that’s going to have to be in the cards sooner than later....
     
    Last edited: Nov 8, 2018
  10. triode17

    triode17 Super Member

    Messages:
    1,301
    Have you changed the octal sockets yet? You may have lost the control grid connection.
     
  11. UncleBingo

    UncleBingo AK Subscriber Subscriber

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    IIrc , the cathode-stripping thing was largely de-bunked for consumer tube gear; having it's roots based in valid concerns inherent in high-power broadcast transmitter tubes.
     

     

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  12. twiiii

    twiiii Addicted Member

    Messages:
    6,209
    Location:
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    Mcintosh used Thermistors to prevent the rush of current to the tubes when first turned on. A friend of mine used a Variac for his Dynas. Yes tubes should be brought on line gradually. At the radio station all the miniature tubes ran 24/7. Only big power tubes for amps etc was the B+ turned off. The heaters remained on. turn tables were left on in broadcast studios, not in the recording studios. We always had three turntables in each broadcast studio in case one gave up the ghost. I use to have 2 turntables, but only have one now. My Thorens TD-125 II has never let me down though it approaching 50 years old. We started out with Two broadcast studios and one recording studio, but the station added FM we tried to get by and it didn't work and using the recording studio was a real pain as a backup. So engineering and record storage got moved to a new building and engineering became the 3rd studio with the wire less links to the transmitters in case the phone lines went down. I admit it was a pain to walk. half way down the block when looking for tubes or searching through the historic record library. We just couldn't do our old time live request show anymore. Eventually we put two turntables in the library and a small Urei board in for request shows, which were more popular than management had thought. I wonder what happened to all those 78's and 45's. There were numerous 33's, but nothing like the 78's.
     
    Last edited: Nov 9, 2018 at 1:08 PM
  13. AdamAnt316

    AdamAnt316 Collector of heavy things Subscriber

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    Location:
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    Not as of yet. I have tried tightening the pin connections, as well as re-soldering the joints which connect to them. I'm not sure if this has solved the problem, as I haven't had a chance to test it since said adjustments were made, though I intend to do so soon. Also a matter of finding a matched set of suitable octal sockets (preferably Amphenols, if possible).
    -Adam
     
  14. triode17

    triode17 Super Member

    Messages:
    1,301
    I used ceramic, Japanese sockets from Angela, including the rectifier socket. Most importantly, did you add 100 Ohm resistors in series with the Screen Grids yet? This has prevented any red plating now for years, in all my amps.
     

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