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Leaving Amp On During Breaks-Yes Or No

Discussion in 'Amps and Cabs [BG]' started by TCollins, Jul 27, 2000.

  1. TCollins


    Apr 4, 2000
    I was wondering...Is it a good idea to turn off ALL power during a 15 - 20 minute break to allow a SS amp head to cool down (my amp never gets very hot to begin with)? How about tube amps? Should one just leave it on "standby"? ...
  2. SS amps - turning it off doesn't hurt it, leaving it on probably doesn't hurt it either. I'd leave it on.

    Tubes - Leave it completely on for short breaks, even up to an hour or more. Turn it all the way off when done completely. Don't flip off the standby switch and leave it. Cathode poisoning can occur that shortens the life of output tubes. Cathode poisoning can occur when the tube filament is left on, but there is no plate voltage to suck the electrons away from the hot cathode. It supposedly forms a coating on the cathode that does not emit electrons very well. Use standby switch on power up, then leave it full on until cutting it full off. Standby switch on power up prevents cathode stripping, where the plate hi voltage pulls or strips electrons off the cathode as it is heating up, eventually damaging the coating and weakening the tube.

    I didn't know this for years, and my tube amps still worked fine, even leaving them on standby for hours at a time during gigs and practice. So it may not be too critical, but that's the technically correct shpiel, and it's what I follow now.

    murphy likes this.
  3. i totally agree with your tube amp procedure. that is exactly what my amp tech told me.
  4. Scok


    Apr 20, 2000
    So Throbbinit (I think I spell it right?)

    Anyway, are you saying that I should not turn off my standby when shutting my amp down? I usually put it on standby for 1-2 minute before I shut down for good. Is it better just to shut down from full power?


    Tube life is all life.
  5. Doug


    Apr 5, 2000
    Buffalo, N.Y.
    Scok, that's exactly what's he saying. Turm off your amp using your on/off switch and not the standby.
  6. when you turn it on: hit the power switch...give it a minute or two, then flick the standby.

    when you're shutting it off completely, do it in reverse order: hit the standby switch, then shut off the main power.

    according to my tech, you should hit the standby prior to shutting off the main power...and based on his credentials, i tend to go along with whatever he says.

    [This message has been edited by Sapo (edited July 28, 2000).]

    [This message has been edited by Sapo (edited July 28, 2000).]

    [This message has been edited by Sapo (edited July 28, 2000).]
  7. i'm no tech, so i can only repeat what my tech says about the amp (v-4b) he worked on for me.

    [Edited by Sapo on 02-09-2001 at 02:10 PM]
  8. I have to play a 3-set gig this Friday night, with 15-20 minute breaks in between each set. Should I turn off my SWR SM-900 in between sets? It gets really, really hot during a normal practice, I'm almost afraid to leave it on that long, of course I will be giving it a 15-minute rest every hour.. what do you guys think? I couldn't discern a clear answer from the above posts, and I've never had to use my amp for this long (we usually practice for two hours at a time.) Thanks for any guidance you can give. BTW the amp doesn't have a standby.

    [This message has been edited by Dave Siff (edited August 01, 2000).]

    [This message has been edited by Dave Siff (edited August 01, 2000).]
  9. "throbbinut,
    What about amps that are cathode biased? Any 'coating' is going to get blasted to hell by a major voltage swing across the plates."

    Yep, when a cathode biased amp is turned on, there is a period of time when the amp is running without correct bias. If the cathode bypass cap is insanely large, it is an even longer period. But, I don't think it's that big a deal. It's not like it only takes once or anything. It's an accumulated effect. My 1979 Fender Musicmaster Bass amp is cathode biased, and it has no standby switch. So it gets the double whammy on each power up. And even so, it still has the original Fender tube set in it and works great.

    As for power down method, it probably doesn't make a damn bit of difference. If I'm about to work on the amp, I just kill AC and leave Standby on to drain the filter caps. If I'm about to put the amp in the closet for a year, I kill standby and then kill AC, so the filter caps will retain a charge for a little while. If electrolytics are stored for long periods of time, they "un-form", and have to be re-formed before use. My little trick probably doesn't do any good in the scheme of things.

    As for cathode poisoning, I heard about it on Rec.Audio.Tubes. I don't dismiss it, but it is probably not a big deal either.

    Here is one thing I know, when you open a switch that is feeding an inductive load, you get a surge and usually an arc at the switch. In Fender Bassman amps, the standby switch feeds directly into the output transformer primary center tap, and filter choke. Not having the switch go directly into a capacitor prevents a surge when the Standby switch is turned on. But I think the pop that is heard when standby is turned off is due to the inductive spike when the switch is opened. For this reason, I leave the standby switch "on" when I power down, to protect the switch.

    Just as an aside, tubes last a hell of a lot longer than people think they do. But I still try and treat them nice.

  10. Dave,

    I leave my SVT-III Pros on during an entire gig (three sets) with no problems. They are hybrid amps. I don't know if this helps or not. I have no experience with SWR gear.

    I'm still in a quandary over the proper shut down procedure for my V-4B! confused.
  11. <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Sapo:

    I leave my SVT-III Pros on during an entire gig (three sets) with no problems. They are hybrid amps. I don't know if this helps or not. I have no experience with SWR gear.

    Thanks Sapo.. I needed to hear someone say it was OK to leave it on. My SWR is a hybrid amp too.

  12. Doug


    Apr 5, 2000
    Buffalo, N.Y.
    Dave SS amps you can leave on. When I used mine, I never shut it off between sets.

    Sapo, turn the amp on while it's in standby and let it sit for 30-60 seconds, before flipping the stand by switch on. Turn amp off by on/off switch, not standby. Turn standby switch to standby after shutting down.
  13. I use SS amps only. I don't turn them off until the gig is over. When we take a break, I simply turn the volume knob(s) on the bass all the way down and put the bass on its stand.

    According to a number of EE's that I work with, you will probably won't gain or loose anything with SS amps leaving them on or turning them off, if everything is working as it was probably designed to do. However, they told me that if things weren't working quite right, you could could cause some minor damage each time you turned the amp on with power spikes, etc. Would you every really notice it? They said, maybe, maybe not. Too may variables to say. So, not being a EE or an amp tech, I turn it on at the start of the gig, and off at the end.

    Just thought I pass this on.
  14. White_Knight


    Mar 19, 2000
    Right on, Sammy.
  15. DaveB


    Mar 29, 2000
    Toronto Ontario
    Sammy - just a point of clarification. Does your gig amp have a tube pre-amp. And would you also leave it on if it does?
  16. Dolan


    May 23, 2000
    Vienna Md
    Wow!!Another subjective subject that doesnt seem to be going anywhere.Isnt it weird how *some* amp techs have different opinions?Isnt it also weird how *some* rag on each other?Seems like the most successful ones get reamed the most.Is this jealousy guys?Some think what they say is GOD and what others say is total bulls**t.From what I have read on here it seems there is no right or wrong way.

    Here is what I do.........tube amps when I am on break.....standby baby.....( I tend to think the amp manufactuers know what they are doing, why the hell would they put them there? )never had a problem doing it that way yet.SS I just leave em on when I am on break.I have even left tube amps on and ss for days ( I know so shoot me ) and suffered no repercussions.If something is wrong its gonna tear up no matter what you do.Is what I am doing wrong?Probably not but it just may be.
  17. sic and twiztd

    sic and twiztd

    Jul 28, 2000
    i have no idea what you're saying. i use my sisters guitar amp to play bass, when i am borrowing my friend's Fender.
  18. DaveB: My gig amp is 100% SS. Even if it wasn't, I would still leave it on.

    I worked as a Radar Technician in the Air Force back in the '60s. The vast majority of the equipment that we had back then was tube powered with point to point circuitry. The tubes in the equipment that was on 24/7 lasted a lot longer than the tubes in the equipment that was fired up once in a while and then shut off. The heating/cooling cycles create mechnical and electrical stress on the tubes. Each individual tube will react differently to the process. Some will last, some won't. But overall, the 24/7 ones lasted much longer in terms of hours of operation.

    I currently work as a Logistics/Reliability/Maintainability Engineer for an electronics defense contractor. My experience, and the words from design EEs tells me that the less cycling a piece of electronic equipment experiences, the longer, on average, it will last. Most of the electrical/mechanical stress that takes place happens during turn-on/warm-up and shut-down cycles.

    So, when I have used tube amps in the past (never owned a hybrid amp), I still left them on during a gig.

    You will find all sorts of opinions on this. Do some research for yourself and decide.

    Good luck on your choice of operation.

    Keep Thumpin'! Sammy!
  19. Preach it, Sammy. You speak the truth.

  20. Laker


    Mar 23, 2000
    I turn my Aguilar preamp on as soon as I can before the gig (to warm the tubes up) and don't shut it or my Crown K2 off until the gig is finished. The K2 goes to "sleep" after a few seconds with no signal to it. The Aguilar has a mute switch so once volume level is set on the bass, I never turn that down on breaks either.

    Just my two hundredths of a dollar.

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