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| | |-+  Why a rectifier tube AND a standby switch?
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Author Topic: Why a rectifier tube AND a standby switch?  (Read 8335 times)
Graylion
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« on: May 10, 2010, 05:52:36 PM »

I'm a newbie who knows his way around point-to-point wiring with a soldering iron,  Grin  but with a very limited knowledge of electronics.  I always thought that a standby switch was only used with a solid state rectifier but shouldn't be used with a tube amp.  I've even read that you should not have one on an all-tube amp.  Opinions please  Huh?  By the way, isn't Nik brilliant at answering questions at any hour of the day or night?  One time is was later than 2am his time! Cheers, Lionel
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wyatt
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« Reply #1 on: May 11, 2010, 06:43:27 PM »

I haven't a clue where you read your information,but it's flat wrong.

Most people will tell you the whole point of a Standby switch is to allow the heater current to the tubes and let the tubes warm up before you hit them with full B+ voltage (which is what the Standby switch turns on and off).  The theory is cold cathodes can be stripped over time by the high voltages.  So, the procedure is to turn the amp to standby, turn the amp on and allow a good 30 secs or more for the heaters to work before turning the standby off and applying the B+ voltage.  There is no optimum power down procedure, because there is no plus or minus to turning off the B+ voltage before the heater current. 

However, as many long stated facts in the guitar world, it seems this is pointless.  The idea of Standby switches saving tube life by preventing cathode stripping was discarded by  the hi-fi world over 50 years ago.  It's very rare to tube hi-fi amp with a standby switch (though some modern high-end equipment will have slow ramp up circuits).  And all tests to try and prove cathode-stripping of cold tubes has come back negative.  There is NO laboratory evidence that using a Standby switch or not saves or kills tubes.

But chances are that's NOT why they added them to tube guitar amps.  The Standby switch is on a guitar amp so that you can turn off the high B+ voltages between sets.  It is called STANDBY because that is exactly what it is there for...when you aren't using the amp, but aren't ready to turn it off. 

So, common believe is Standby's are on tube amps to preserve tube life, though they probably don't. They are really there so you audience doesn't here 60-cycle hum while you take a piss break.  But they definitely DON'T hurt the tube amp.  And they are almost exclusively used on tube amps. 

Now, for those who believe in cathode stripping, the 5V4, 5U4 and 5AR4 tubes rectifiers offer slow votlage ramp up, so a Standby doesn't have to be there because the rectifier takes a while to deliver full B+ anyway.  But the 5Y3, like on a Champ, well, that's a fast ramp up tube. 
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Graylion
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« Reply #2 on: May 15, 2010, 05:39:00 AM »

Thanks Wyatt but you're actually confirming what I had read.  With a tube rectifier a standby switch isn't needed due to it's slower warmup time compared with the almost instant (? - much quicker) solid state device.  When these are used you would have an argument with other electronic experts I know about the powering off procedure!  Not me because I haven't got the the knowledge!
I have spoken to Nik about this subject and he has agreed that a standby switch isn't really needed with the Ceriatone all-tube amps.  It's just "tradition" he put it.  It is also not needed for low power amps such as the 5 watters even with solid state rectifiers.  This info is from a guy who designs and sells amp kits, which are solid state rectified, but have no standby switch - even with 18Watt "Plexi" clones.  About his 5 watt kits not needing tube rectifiers he said there was no need "..because there's no sag in such amps."  I guess that will mean more to you than it does to me!
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wyatt
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« Reply #3 on: May 15, 2010, 06:20:21 PM »

Pure and simple what you should take away from my thread.  Standby is great if you play live, because you can put your amp in standby between sets keeping your tubes warm and avoiding subjecting your audience to the possible loud pops as filter caps discharge when you turn off.  It is what it says it is a standby switch, not a power up/down switch. 

If friends are actually electronic experts, they wouldn't see the point of a standby switch for powering up or down anyway.  Smiley
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Graylion
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« Reply #4 on: May 18, 2010, 06:41:52 AM »

Thanks Wyatt, I do see the use of a standby but it was always explained to me (by electronics "experts") that it was needed with tube amps that had solid state rectifiers to avoid sudden voltage surges (??) and damage to the tubes.  It seemed that its secondary use was to power down temporarily when at a gig.
Nik and the other guy both make/design/sell tube amp kits and both say the standby switch isn't needed, but for different reasons!  Some players and techies who write for magazines warn of dire problems if an amp is powered up without the standby switch in the "On" positions!  Ditto for powering down - do it wrong and your head will explode!! Grin  Joking of course, but opinions seem to vary.
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wyatt
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« Reply #5 on: May 22, 2010, 02:55:13 AM »

Thanks Wyatt, I do see the use of a standby but it was always explained to me (by electronics "experts") that it was needed with tube amps that had solid state rectifiers to avoid sudden voltage surges (??) and damage to the tubes.  It seemed that its secondary use was to power down temporarily when at a gig.
Nik and the other guy both make/design/sell tube amp kits and both say the standby switch isn't needed, but for different reasons!  Some players and techies who write for magazines warn of dire problems if an amp is powered up without the standby switch in the "On" positions!  Ditto for powering down - do it wrong and your head will explode!! Grin  Joking of course, but opinions seem to vary.


Opinions have varied for decades.  As have theories of cathode stripping with the sudden rush of B+ voltage (though it hasn't ever been proven in lab tests).  But the hi-fi world wrote it off as bunk a half century ago.  It's mostly guitar amp techs (yet not designers) who persist in arguing for cathode stripping.

BTW, a 5Y3 or 5U4 rectifier tube will deliver voltage almost as fast as a SS rectifier.  It's the 5AR4/GZ34, 5R4 and 5V4 that have "slow ramp up."
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Geosixs
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« Reply #6 on: May 19, 2020, 02:55:53 AM »

May your friends be encouraged to live life. And get through it Today is a good opportunity. Would like to introduce.
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