How to properly start up an SVT Classic Head

Discussion in 'Amps [BG]' started by beerthebear, Feb 18, 2014.


  1. beerthebear

    beerthebear BEADG

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    Hi,

    I've recently bought a SVT Classic Head and have a question. I'm relatively new to the tube game, as I've used solid state amps in the past (or hybrid amps). Those were easy to start up, just flip the switch. However, with this all tube amp, I've read conflicting ways to start it up.

    In the manual there is this concept of "Stand-by." I'm assuming that standby is when you flip the standby switch and no sound comes out of your amp. What I don't understand is why it is in "standby" when the switch is set to "0" instead of "l"? Also, I've read that your supposed to start the amp with standby off, and only switch to standby once it has warmed up a bit. Is this the proper way? I'm just making sure I have this right, this is an expensive amp (lovely sounding as well), and I want to make sure that I treat it with the respect she deserves =)

    I'm assuming that I need to flip the Power switch from "0" to "l" if and only if the standby switch is already positioned at "l" (with standby off). Your validation, or corrections are greatly appreciated.
     
  2. InsanityAmps

    InsanityAmps Supporting Member

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    The proper way is to turn the power switch to the on position(1) first with the amp on standby(0). This lets the tubes warm up. After a minute or so turn the amp off standby(1) and you are ready to rock. Just think of the standby switch as another power switch which it is. It turns on the high voltage to the tubes.
     
  3. BurningSkies

    BurningSkies Supporting Member

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    Feel free to ignore that switch.

    You'll read a lot about tube amps needing to warm up before 'taking out of standby' .They really need all of about 10 seconds.

    I own a bunch of tube amps that don't even have 'standby'. It's handy when you want to have a set break and leave your amp on and muted though.
     
  4. InsanityAmps

    InsanityAmps Supporting Member

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    Try to confuse him even more! There has been heated debates on whether or not standby is necessary but the original question is what is the proper use of the standby switch which is what I explained above. I like using standby on amps without a tube rectifier. Why? Maybe not necessarily to save the tubes but the filter caps. With no load on the power supply the B+ voltage can be considerably higher than when the tubes are conducting. A well designed amp will have electrolytic capacitors rated far enough beyond the B+ voltage that there is no issue but that is not always the case and I've seen more than a few amps that will exceed the voltage rating on the filter caps if they are turned on without the amp on standby. A tube rectified amp doesn't really need a standby since the high voltage comes up slowly as the rectifier tube warms up.
     
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  6. negativefx

    negativefx complete hack Gold Supporting Member

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    I've also heard that you should ignore a sports car's 1000mi 'burn in' time and just rap it out right off the lot.

    Fact: I use the power and standby switches as directed by the manual and have never blown a power tube. Yes, I've replaced tubes, but before any failure ever happened.

    Opinion: Ignoring manufacturer's recommendations is totally fine and won't cause any problems.
     
  7. BurningSkies

    BurningSkies Supporting Member

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    Fact: I've never 'blown' a power tube either.

    Fact: I currently own 3 tube amps and 2 high voltage tube pre-amps. Of those, I have 2 standby switches, the rest do not. I've also had a few other tube amps with a couple tubes in them each... SVT and a 400+. None had any trouble from 'standby disregard'.
     
  8. bachlover

    bachlover Supporting Member

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    I was in the same position as the OP and found the instructions manual to be somewhat confusing. This issue has been posted before as it's not clearly outlined by Ampeg. I sympathize with the OP as I want to follow the manufacturer's instructions, and after doing the opposite, finally found the correct procedure thanks to the great posts regarding this.
    - start up with amp in standby mode (ie. switch down, no sound)
    - after 30 sec. or so, flip the switch, taking the amp off standby so you can hear it.
    - when shutting down, leave the switch off standby to allow the capacitors to drain.
    - after 30 sec. or so, flip the stanby switch to the "on" position.
    I suggest you search "standby ampeg" on this forum and read what else has been said about this, but I think I've pretty much summed it up. One poster also suggested that if you hit the low B (or E) string while you switch it off, it'll drain the caps faster. I understand your concerns, hope this helps!
     
  9. dukeisdog

    dukeisdog Supporting Member

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    But why when it is suggested and only takes 30 seconds or less? I flip my amp to standby and start on getting my pedalboard ready/plugged in, then I tune up, etc, by then, my amp is ready to go.

    My new Mesa Prodigy suggests 5 minute warm up time, surely I wouldn't disregard a disclaimer like that from the manufacturer.
     
  10. beans-on-toast

    beans-on-toast Supporting Member

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    It is far more important to have a good clean source of power for your amp to draw on. So check that first. Some people go so far as to use an inexpensive outlet tester (available at hardware stores for under $10) to ensure that the mains wiring is correct.

    Next thing to do is to let your amp acclimatize. If you live in a cold climate, let it warm up to room temperature. Thermal shock isn't good for the tubes.

    Since you have a standby switch, use it. Take thirty seconds in standby for the tubes to warm up. It ain't going to hurt them.

    What does standby do? It turns on a heater inside each tube. This heats the cathode to a temperature that allows electrons to boil off. When free, they fly to the anode. Well, its more complicated than that. The heater needs to be on for the amp to work. When you switch it out of standby, the heater continues to work, also the high voltage (B+) power supply is turned on. The high voltage also makes the tubes work. IT makes the cathode electrons fly to the anode. Opposites attract. The anode is positive, the cathode electrons are negative.

    To shut down the amp, turn off the power. If it is cold out, let it cool down before taking it outside. That thermal shock thing again.

    It helps to protect the amp from the environment. A slip cover is good. A case is even better.
     
  11. BurningSkies

    BurningSkies Supporting Member

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    This. I actually have a few outlet testers, and my gigging rig has one plugged into one outlet of my power strip at all times. I plug in at a show and I can instantly tell if there's bad wiring. The others in my gig bag test out the other outlets on stage so I don't 'cross wires' with any other band members or the PA.

    Also, I agree that you don't want to go from 'winter cold' to inside/stage temperature without letting your amp (AND bass) warm up.
     
  12. BurningSkies

    BurningSkies Supporting Member

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    My Mesa 400+ also told me that I had a 400+ watt amp.

    I think that tube guys love the ritual of the whole thing. But its not worth someone freaking/obsessing/losing sleep/worrying about the standby.
     
  13. Pearly Gator

    Pearly Gator

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    A couple more things;

    When done playing, shut off your tube amp and let it cool for 20 minutes before moving it. Bumping around gear with hot tubes can damage them. The grids are thin and when hot, can be knocked out of alignment or even short.

    Speaking of 20 minutes, I personally find that tube gear sounds best after it is warmed up and running for 20 minutes. The temperatures are stable and I can hear the difference. YMMV, IMHO, I have dog ears, etc.

    Enjoy the world of tubes.
     
  14. Jim C

    Jim C Supporting Member

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    In addition to the standby on for 30 seconds before mains, I have also been told that going to standby for a few minutes after playing allows for the fan to cool the tubes more gently.
    Moving a hot tube amp, powered or not, is definitely not good for any tube IMO/IME.
     
  15. Pilgrim

    Pilgrim Supporting Member

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    My experience with tube gear goes back to the 60's when almost everything used tubes.

    A little warm-up period does indeed allow tubes to stabilize, but once it's on and making sound, you can play through it. If the tubes do "stabilize", a few minutes is enough, and it would normally take "dog ears" to hear the difference.

    I agree that with any amp containing tubes, a short cool-down period can help preserve tube life. 5 minutes is plenty...all you want to do is let the tube's internals cool off enough not to be vulnerable, and that's enough. Shut down, pack gear, and you're good to go.
     
  16. groovaholic

    groovaholic Looking for a band... Supporting Member

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    Not to insult the experience or expertise behind the other advice you've gotten, but...

    Amps are an engineering task -- the SVT was state of the art in 1969 and still makes some significant demands on the tubes; the 6550s are running a plate voltage upwards of 600 VDC.

    Hitting those tubes with the full 600+ volts before they are warmed up might not hurt them, but it won't do them any favors either.

    The advice from "Insanity Amps" was written by a guy who has built a 1,000 watt monster tube amp FROM SCRATCH !

    The Insanity Amps amp pushes things much farther and much harder than an SVT, so his advice is the safest guidance you're going to get.
     
  17. Sid Fang

    Sid Fang Reformed Fusion Player Supporting Member

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    Though that's only important if you intend to open up the amp for repairs. Having the caps charged between uses isn't a bad thing - indeed, it can be a *good* thing for the life expectancy of electrolytics, IIRC.
     
  18. catgut

    catgut

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    You do. At about 30% THD. :hyper:
    Just saw a 400+ on bench measured at 463W completely cranked. Under 10% saw the amp hit 340W or so usable and others about 306W. I think they all kind of vary given the reports. Maybe you got a limp one.
     
  19. BurningSkies

    BurningSkies Supporting Member

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    Its long gone now. :)

    They really bench clean to about 275-300 on a good day. No matter what the 'manual' says.
     
  20. catgut

    catgut

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  21. BurningSkies

    BurningSkies Supporting Member

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    Yep. I've seen that. That guy does some really good videos.

    It all depends on what amount of clipping behavior you find acceptable and/or if you don't mind them rating their amp based on 'peak' ratings. ;)

    That's way more frequent these days than it was say a few decades ago when Mesa produced the amp...and the manual which tells you that you need to replace the tubes frequently and only use Mesa sold ones. :crying:
     

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