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Best way to turn on and turn off a tube amp?

Discussion in 'Glowing Bottle Tube Amp Forum' started by HotRodSteve, Jan 31, 2014.

  1. HotRodSteve

    HotRodSteve Friend of Leo's

    Sep 24, 2013
    The Hudson Valley
    What is the best way to turn on and turn off a tube amp? Would it be to flip the switch into Standby mode and then flip on the power switch? And to shut it off would it be to put the amp into Standby mode for a few minutes and then shut off the power switch?
     

  2. PinewoodRo

    PinewoodRo Tele-Afflicted

    Yes. Mains first, wait a minute or two, then standby. Standby off first, then mains.
    If you use this method then the standby is always off when you sitch the mains on again.
     

  3. waparker4

    waparker4 Doctor of Teleocity Ad Free Member

    Nov 9, 2011
    Philadelphia, PA
    No need, just shut it off making sure its in standby mode before you turn it on again.
     

  4. steveneddy

    steveneddy Tele-Meister

    235
    Jan 16, 2012
    Texas
    Shutting DOWN an amp you WANT to use your standby switch.

    Taking care of the tubes and circuitry powering the tubes is the most important part of tube amp ownership.

    It is a ritual that we all perform to ensure long tube life and prevent costly repairs at the tube amp repair shop.

    We all know that starting an amp by leaving the standby switch on all the time and flipping the mains on and waiting for everything to "warm up" is putting more voltage into the tubes than they were designed for - and since they are cold they have no way of protecting themselves. They die a premature death and the end user generally blames a tube company or that "crappy amp".

    Whatever - we'll move on.

    Tubes need a cool down also before shutting down. They don't need a long period of time - but 30 seconds should be sufficient.

    Start up? I generally wait two minutes or more - the tubes are physically warm at that point and the voltages have stabilized sufficiently to amplify sound - then hit the standby switch to start playing.

    These are my opinions - you can treat your amp any way you like - it's YOUR amp.
     

  5. hshight

    hshight Tele-Meister

    379
    May 25, 2010
    near Memphis
    1967 Bandmaster - blackface circuit - should it pop when I go from standby to on?
     

  6. waparker4

    waparker4 Doctor of Teleocity Ad Free Member

    Nov 9, 2011
    Philadelphia, PA
    The purpose of the standby switch when powering on is to warm up the tubes. The standby switch leaves the heaters ON. Putting the amp in standby will not cool down the tubes....
     

  7. bblumentritt

    bblumentritt Tele-Afflicted

    Dec 3, 2012
    Austin, Texas
    It depends.

    Do you have a Bandmaster or a Bandmaster Reverb? A '67 Bandmaster used a solid-state rectifier, while a '67 Bandmaster Reverb used a 5AR4/GZ34 rectifier.

    6L6 and 12A_7 tubes have an 11 second warm-up time for their heater. A GZ34 is an indirectly heated cathode rectifier, which has a controlled warm-up time before it starts passing high voltage. Fifteen seconds is enough time to allow heaters to come up to spec.

    The standby switch allows the HT(B+) to be turned off while the heater supply, and bias supply if applicable, is on. The idea is that if the HT is applied while the cathodes are cold they will be 'stripped' by ions crashing into the unprotected cathode, and effect known as Cathode Stripping.

    If you're using an indirectly heated tube rectifier (GZ34, Sovtek 5Y3), it shouldn't be passing HT anyway until the heaters are warmed up, thereby negating the use of a standby switch.

    Directly heated rectifiers produce HT more quickly, and solid-state rectifiers produce HT almost immediately, so the standby switch is thought to be necessary.

    However, there is some controversy about standby switches. The whole idea of cathode stripping may be moot for receiving tubes, as cathode stripping was applied to transmitting tubes, and not receiving tubes. )6L6, 12A_7, 6V6, EL_4, etc are receiving tubes.)

    The RCA Transmitting Tubes Technical Manual No. 4, p65, states: “Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature.”​

    So, cathode stripping may not be an issue after all, again negating the necessity of the standby switch, and the standby switch may be nothing more useful than a mute switch. A more effective design would be to use a limiting resistor, and Peavey uses a form of this on their tube amps that don't have standby switches.

    Now, on to the "pop". The standby swtich is probably not rated for HT DC. They're usually rated 5A 125VAC, not for 500VDC. Furthermore, Fender standby switches are directly on the B+ supply, in series with the smoothing choke, and don't have any transient shunting capacitors or fly-back diodes on them.

    When the standby switch is thrown, one end of the choke is left completely unconnected to anything. Not only is this likely to lead to pop sounds, but the choke can develop a massive fly-back voltage which can cause serious arcing in the choke and switch.

    If you want to eliminate standby switch popping, attach a capacitor between the upstream side of the standby switch and chassis ground. This will shunt transient voltages and high frequency interference to ground, and also provided a small load to the power supply so you can measure the B+ voltage at standby. A 0.033µF capacitor ensures that most frequencies will be passed through. Very high frequency signals, such as TV signals, will add noise to our signal. These are filtered out by this capacitor, which has much less ESR (Equivalent Series Resistance) than electrolytic capacitors at high frequencies. Adding a snubbing diode in parallel with the choke to prevent fly-back voltages could also help alleviate the issue.

    Bottom line.

    The easiest way to prevent popping is to either not use the standby switch, because you have a GZ34 rectifier, or to use a 0.033µF shunting capacitor between the upstream side of the standby switch and chassis ground.
     

  8. hshight

    hshight Tele-Meister

    379
    May 25, 2010
    near Memphis
    Non-reverb, so ixnay on the itchsway, I suppose.
     

  9. muchxs

    muchxs Doctor of Teleocity

    Aug 14, 2004
    New England
    I got tired of the standby / no standby debate. I just yank the cord outta the wall now. :twisted:


    Seriously, using the standby switch unloads the power supply in some amps. Some of 'em are pretty close to the voltage limit of their filter caps, loaded. If your caps are 450v and the amp drifts over 450v on standby... that ain't a good thing.

    That's why Twin Reverbs are designed to withstand 700v on the first filter.
     

  10. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Since I don't play amps with old electrolytics and since there is no reason to warm tubes up before applying full voltage, I find no reason for a standby switch on any tube amp. As I understand it, it takes 10,000 volts to 'strip' those cold cathodes of precious metals, and no guitar amp operates with those voltages. There is no such thing as 'cathode stripping' in these amps of ours. There are numerous sites that explain this.
    On the other hand, leaving an amp in the stand by mode for extended periods can assuredly cause something called 'cathode poisoning' which degrades the tube. IF an amp has a standby switch, I might use it to remove/install a tube or unplug/plug in a speaker...but for no other reason is a standby switch needed.
     

  11. SamClemons

    SamClemons Poster Extraordinaire

    Jan 23, 2011
    Jasper, TN
    I have flipped both switches on and off simultaneously for years. I don't think it makes a whole lot of difference.
     

  12. jackleg

    jackleg Tele-Meister

    364
    Aug 19, 2004
    when turning off, just turn off!!! only think about standby when you power up....
     

  13. joeford

    joeford Friend of Leo's

    Apr 17, 2013
    st. louis, illinois
    what's normal warm up time on a tube amp? i usually just wait about 30 seconds or so before flipping the standby switch.

    thankfully, my newest amp has a 3-way toggle for the power switch. off-standby-on. i can't second guess the ritual of powering on and off... i have to take a visit through the world of standby both ways
     

  14. Triton Thrasher

    Triton Thrasher Tele-Afflicted

    Sep 8, 2010
    Wick, Scotland
    Why isn't the 11 second delay and change from "standby" to "on" done automatically by amps?

    And why is standby un-necessary on valve amps with no standby switch?
     

  15. bblumentritt

    bblumentritt Tele-Afflicted

    Dec 3, 2012
    Austin, Texas
    6L6 and 12A_7 tubes have an 11 second warm-up time for their heater.
     

  16. bblumentritt

    bblumentritt Tele-Afflicted

    Dec 3, 2012
    Austin, Texas
    Limiting resistors do this "automatically". Peavey uses a form of this on their tube amps that don't have standby switches.

    So do indirectly heated tube rectifiers, such as a 5AR4/GZ34 and the Sovtek 5Y3 (but not true 5Y3 tubes, which are directly heated). These rectifiers have a controlled warm-up time (11 seconds) to match the warm-up time of the other indirectly heated tubes, such as 12A_7, 6L6, EL_4, and 6V6 types. The indirectly heated rectifier isn't passing HT anyway until the heaters are warmed up, thereby negating the use of a standby switch.
     

  17. Coop47

    Coop47 Poster Extraordinaire

    Apr 10, 2009
    Boston
    I turn the standby off when turning off just so that it will be off when I turn the amp back on. As I get older, I need to rely on ritual to get me through certain processes.
     

  18. BartS

    BartS Friend of Leo's

    Feb 18, 2013
    St. louis MO
    it's a tube amp no matter what you do every 2-4 years it will need new power tubes and every 4 to 10 years it will need either a new cap or a transformer or something that the average person can't fix on their own that will cost some serious scratch to get fixed. Just plan on it. It's called maintence.
     

  19. muddyh2o

    muddyh2o TDPRI Member

    94
    Jul 25, 2010
    houston,tx
    Fairly we'll know fact with an ac30. Excluding the new c series. If you use the standby switch it will blow the rectifier tube.
     

  20. wtk0315

    wtk0315 Tele-Holic

    512
    Sep 21, 2013
    Houston area
    I laughed when I read that they put standby switches on the newer classic series and delta blues, not because they needed them but because so many guitarist wanted them.
     

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