Tube Amp myths...

GuitarStv said:
There is little real need to warm the vast majority of tube amps, and no reason at all to use the standby switch. :P
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My buddy had his Marshall for years with no problems. Then his kids started using it and never put the amp in standby. All of a sudden the amp started blowing fuses they wouldn't last more than a few minutes before blowing. The bench tech could never figure it out.
 
ehdwuld said:
Dangit Stv
my tube amps are bit sterile when I first turn them on
When they warm up for a few minutes
The bloom comes back

Of course it could be my playing is stiff and sterile
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He’s not saying the tone doesn’t change (in my experience it does too, as everything warms up) but that having the tubes heaters on for a while before applying high voltage is not necessary.

Now the interesting thing is that if you have a tube rectifier, the voltage naturally ramps up as the rectifier has to warm up as well. On a solid state rectified amp, it is more instantaneous.

Correct me if I’m wrong, but when you dig into the history, everyone keeps including them because that’s how the previous amps did it, right?
 
Standby is actually very handy for some troubleshooting methods.
There is a video from Mesa showing their tech use it like that.
 
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PFDarkside said:
This feels a little Ali G, doesn’t it?

Well for number 1, as others have said it’s a misunderstanding of needing to have a load connected when powered on.

For number two, as caps and tubes age, the chances of them “popping” is statistically more likely when it’s powered up than when it’s not, right? ;) It’s not surprising that the inrush of current may cause failure, but what are you going to do? Unless the working theory is that amplifiers that are used daily are less likely to fail catastrophically? Eventually tubes and caps and other things will fail. On that note, it’s good to be aware when things are going downhill. You might be able to shut it down before damage to other components like the output transformer occurs.
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This is what I meant by popping....component failure..capacitors, fuses, a tube...
 
From too long of non-usage and/or bad storage conditions you can have filter caps drain their charge and then dry-out, and then that can cause a failure which can take other stuff with it.

How long is too long for the amp to not be used? I have no idea.
I let my tube amps go months at a time without running, but I rotate them so each one gets it's turn for awhile and none of them really go too long.
Modern caps are better and more durable from what I've read, and it obviously isn't as likely to be a problem if the amp is newer rather than older.
If a tube amp was stored in some ice-cold garage up in Canada for years then it should not be turned on without using a device to lower the voltage until it's had time to recharge itself.
 
Securb said:
My buddy had his Marshall for years with no problems. Then his kids started using it and never put the amp in standby. All of a sudden the amp started blowing fuses they wouldn't last more than a few minutes before blowing. The bench tech could never figure it out.
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I have no idea what your buddie's kids were doing to that poor amp . . . but the fact that the bench tech didn't say anything at all about using the standby switch should tell you volumes about how (un)important it is to do so.




PFDarkside said:
Correct me if I’m wrong, but when you dig into the history, everyone keeps including them because that’s how the previous amps did it, right?
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Yep.

There's no benefit at all to using them to the electrical circuit or components.
 
GuitarStv said:
I have no idea what your buddie's kids were doing to that poor amp . . . but the fact that the bench tech didn't say anything at all about using the standby switch should tell you volumes about how (un)important it is to do so.
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The bench tech is the best in the area. It was a typical amp gremlins situation. At the shop, it acted perfectly. 3 days after being home it started blowing fuses again.
 
That sounds like brown power at house

Low voltage or something loose at the house

The tech has good power on the bench
 
dave74 said:
From too long of non-usage and/or bad storage conditions you can have filter caps drain their charge and then dry-out, and then that can cause a failure which can take other stuff with it.

How long is too long for the amp to not be used? I have no idea.
I let my tube amps go months at a time without running, but I rotate them so each one gets it's turn for awhile and none of them really go too long.
Modern caps are better and more durable from what I've read, and it obviously isn't as likely to be a problem if the amp is newer rather than older.
If a tube amp was stored in some ice-cold garage up in Canada for years then it should not be turned on without using a device to lower the voltage until it's had time to recharge itself.
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Yes I'm thinking this is or was an issue with vintage amps...
 
GuitarStv said:
There's no benefit at all to using them to the electrical circuit or components.
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I've read this too, somewhere. Basically, it IS necessary with large high-power tubes, such as used in radio station transmitters, and people like Leo just brought it along with his designs. But they aren't necessary for low-power applications.
 
I read somewhere that you can't touch tubes with your bare hands and that if you do, you need to wipe the tube off before you turn it on. That true?

The Mesa Tech in this video doesn't use gloves for either removal or replacement.
 
GreatOz said:
I read somewhere that you can't touch tubes with your bare hands and that if you do, you need to wipe the tube off before you turn it on. That true?

The Mesa Tech in this video doesn't use gloves for either removal or replacement.
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Theoretically, anything that's glass that also heats up can be negatively impacted by an uneven distribution of oils (like from your hands). It will slightly change the heat loss through the glass, which (in extreme cases) might lead uneven thermal expansion and cracking. But guitar tubes operate at a low enough temperature that I can't imagine it being much of an issue.
 
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I have seen the skinny Quartz bulbs that he is talking about
and the finger prints on the failed bulb
The halogen light bulbs get super hot

I prefer to error on the side of caution
And I'm a bit OCD about dust

If I do touch the tubes I wipe em off with alcohol before firing it up
 
GuitarStv said:
Theoretically, anything that's glass that also heats up can be negatively impacted by an uneven distribution of oils (like from your hands). It will slightly change the heat loss through the glass, which (in extreme cases) might lead uneven thermal expansion and cracking. But guitar tubes operate at a low enough temperature that I can't imagine it being much of an issue.
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I've always wiped them -my fathers company made the highest end tubes ever made and he was super specific on this -BUT those super high end gold tubes were used more in diagnostic machines like photo spectrometers where uneven heat dissipation through the vacuum can impacted data/results -so it may not affect guitar amp application much at all, although did blow tubes in the earlier days occasionally and they were usually ones I had handled less carefully -but more likely vibration did them in.

and there is a notable thickness difference in different brands (or there was -now that almost everyone is owned by the same company maybe less so) -so I wonder if oils impact different brands differently.
 
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