Tube life and good tones

Re: Tube life and good tones

Brown Note said:
People have been a bit mislead about the stand by and why it's needed. The tube takes about a 10 seconds to warm up, after that the cathode is already at opeartional temperature at which it works perfectly. The current spike cannot happen unless the cathode is warmed up and emitting the space charge. The reason for warm up period is not the prevention of high current spike, but the cathode poisoning that happens when unheated cathode material conducts current. The amp is class A or AB, which means that it conducts current even when no guitar signal is fed through it. It would make a difference, but guitar amps are built no where near the limits of the tubes capabilities hence the cathode is never conducting enough current to really need the warm up period. Even 100W amps don't really suffer from cathode losing it's emission capabilities even when no stand by is used! The ultra high power tube amps are those that require the warm up. The actual current spike happens in the heaters(the heated wire that indirectly heates the cathode) and not a single amp that I know, has current limiting that would prevent the heater wire from suffering the inrush current at startup!

So don't worry about the warm up period. 30 seconds is what you need to use in order to make sure that the cathode is completely heated and even this is beyond overkill as far as tube longevity goes. You almost certainly won't need the warmup at all but it's better to err on the safe side.
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Nice! Thanks for the info. I know that Bogner recommends allowing the amp to warm-up for about a minute before taking-off standby. But I usually went conservative and allowed 5-15 minutes. Won't bother with that now if I makes absolutely no difference in terms of "hurting" the amp or the tubes.

Another question for you (or glassman)... is there a difference in tube and/or other amp component logevity depending on whether the amp is on or off standby? I'm thinking that there must be, because you hear stories of people leaving their amps on for days or weeks accidently, and I would think that it'd be a WHOLE different story if they were ON and not on standby for that long. If for nothing else, than for all the heat generated for that time.
 
Re: Tube life and good tones

Red_Label said:
Another question for you (or glassman)... is there a difference in tube and/or other amp component longevity depending on whether the amp is on or off standby? I'm thinking that there must be, because you hear stories of people leaving their amps on for days or weeks accidentally, and I would think that it'd be a WHOLE different story if they were ON and not on standby for that long. If for nothing else, than for all the heat generated for that time.
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There is...but it depends.

Tubes: in a class AB that is conservatively biased there really isn't a lot of wear on tubes when leaving it on. With a class A or AB amp biased really hot, there can be some wear but no more than what is experienced when playing the amp. Wear is relative to current.

Resistors and poly caps: generally these are unaffected other than the changes they experience during a heating cycle. High dissipation resistors, such as those commonly found in the power supplies for channel switching networks can get hot enough from their own current draw to cause their solder connections to become poor.

Electrolytic caps: heat can actually add life to these if they are lower rated ones (45C, 65C and 85C). Prolonged heating can actually reform them; ever wonder why those 4 section cans in Princeton Reverbs seem to last forever if the amp is played regularly? That's why. Higher rated electrolytics (105C) tend to dry out quicker due to heat; the composition of the dielectric is less resilient the higher the heat rating. The interesting thing is that the heat rating isn't a maximum temperature rating; its a stability rating/value de-rating point. Temperatures over that rating will equate in a reduction in value (uF) which is a majority of what you hear when your amp gets really hot.
 
Re: Tube life and good tones

glassman said:
The sapphire blue corona inside the tube is gas...every tube has it to some degree. You will grow to love the color...it's the color of tone.
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I once played drums behind my old '68 Bassman, and every time the bass player hit a note, the blue light would move. Too cool.
 
Re: Tube life and good tones

glassman said:
All normal.

The orange glow is the filament (or heater). It runs the length of the tube (though you can only see the ends of it) and heats the cathode so it can emit.

The sapphire blue corona inside the tube is gas...every tube has it to some degree. You will grow to love the color...it's the color of tone.
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It look like my filaments are blue....is that possible? The blue color is really thin like a thread and runs the length of the tube.
 
Re: Tube life and good tones

Red_Label said:
*SNIP*
Another question for you (or glassman)... is there a difference in tube and/or other amp component logevity depending on whether the amp is on or off standby?
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Heating the tube is not that big of a problem as they are ment to be continuously used with temperatures of 400F and above! I wouldn't suggest to leave the amp on for weeks at a time, but in a good studio day the amp is on for 5-10h at a time and played quite a lot. Most tube amps are ment for this kind of use. Some combo class A amps that are run really hot at all times suffer from overheating, but most amps don't. Only parts, aside from tubes, that really can overheat are the electrolytic caps. Luckily modern caps, even the bad ones, are so good that they basically don't break with heat unless they are running at the limits of their ratings. This is more of a bad design choise than something that could be avoided by the end user.
 
Re: Tube life and good tones

There are basically three things that affect tube life: cathode wear, vacuum and loose components within the tube.

In theory the cathode material does wear out when it's conducting current, but it's practically never the thing that happens first.The cathode takes several thousands of hours to really be so worn that it cannot be used anymore and this is with continuous use!

Tube loses it's vacuum because the glass envelope leaks a bit, because the different metals aren't completely clean and because stuff is evaporated from the getter(shiny metal on top of tubes). This also takes a LONG time to happen, but some tubes are more prone to this than others. EL34 is known for it's soft vacuum.

The third possibility is the reason for most bad tubes, loose construction. This is what makes a tube microphonic. The actual materials have enough space to move a bit. Glass itself is material with no solid structure, hence it thins with time. Also, when the glass is heated the thinning is more pronounced. The joints within the parts inside the tube also come loose when tube is heated, but these also happen quiter rarely. In most tubes that are well constructed this also takes a *LOT* of time(thousands of hours of continuous use) and bad tubes don't pass the tests.

What breaks down a tube is physical wear, especially rattling and shaking. It greatly enchaces all of the above and wears down the socket of the tube. Rattling happens when amps are moved and mostly when amps are played on top of speaker cabinets. The worst case scenario is with Combo amps with upside down tubes. These can easily have 5 times shorter tube life than other constructions as the heat from the tube rises to the socket which also has to support the weight of the tube and the speaker makes the entire thing shake with. This makes the socket pass gas(hehe) puts stress on the joints and overall is bad for the tubes. Tubes like to be still and cool, even though they run hot.
 
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Re: Tube life and good tones

jimbo1 said:
It look like my filaments are blue....is that possible? The blue color is really thin like a thread and runs the length of the tube.
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The 6L6 is sort of an "open" construction you can actually see the cathode. This also means that some of the electrons aren't captured by the plate structure and bounce from the glass and other materials that they hit. This makes up for the blue glow inside the tube. It's nothing to be worried about. 6L6 is just a tube with a nice blue glow in them. Play them loud and the glow dances with the low bass notes!
 
Re: Tube life and good tones

I have never paid much attention to it or noticed any difference at all.

I put my amp on standby while I'm hooking up my cables and pedal power and such, then get right to it. Sounds the same to me on minute 1 as it does on minute 100.

1996 Fender Hot Rod DeVille
 
Re: Tube life and good tones

ImmortalSix said:
I have never paid much attention to it or noticed any difference at all.

I put my amp on standby while I'm hooking up my cables and pedal power and such, then get right to it. Sounds the same to me on minute 1 as it does on minute 100.

1996 Fender Hot Rod DeVille
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It might have something to do with the stage players getting themselves worked up by the third set, as much as anything to do with the amp.

I still notice that when I've played my amps hard at a show, they get more responsive as the night goes on, and by the third set, they definitely don't sound like they did at minute 1 any more.
 
Re: Tube life and good tones

guitfiddle said:
It might have something to do with the stage players getting themselves worked up by the third set, as much as anything to do with the amp.

I still notice that when I've played my amps hard at a show, they get more responsive as the night goes on, and by the third set, they definitely don't sound like they did at minute 1 any more.
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Maybe my inability to hear a difference is related to me having a huge 60 watt clean amp that never gets turned up very high on the volume dial, even at a gig.

I get my dirt from pedals - works better with this DeVille - it's dirty tones are harsh and thin, but it's clean channel is huge, so I stay there and bump it with pedals.

At any rate, I never turn it up too much, because it's so loud and clean by nature. I have never had it above 3 on the master.
 
Re: Tube life and good tones

ImmortalSix said:
Maybe my inability to hear a difference is related to me having a huge 60 watt clean amp that never gets turned up very high on the volume dial, even at a gig.

I get my dirt from pedals - works better with this DeVille - it's dirty tones are harsh and thin, but it's clean channel is huge, so I stay there and bump it with pedals.

At any rate, I never turn it up too much, because it's so loud and clean by nature. I have never had it above 3 on the master.
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Could be...These days I usually bring a little single ended 6L6 amp I have, and put it on a 2x12. The band plays just to the level of that amp on 10, so it changes over the night.

Even my Music Man, which I run on 3 on the volume, gets hotter over the night and the tone warms up some. I run the preamp pretty hard on that amp, though, and it's a voltage beast (700 on the plates in 150 watt mode) so it gets real warm inside.
 
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Re: Tube life and good tones

Interesting...

glassman said:
Electrolytic caps: heat can actually add life to these if they are lower rated ones (45C, 65C and 85C). Prolonged heating can actually reform them; ever wonder why those 4 section cans in Princeton Reverbs seem to last forever if the amp is played regularly? That's why. Higher rated electrolytics (105C) tend to dry out quicker due to heat; the composition of the dielectric is less resilient the higher the heat rating. The interesting thing is that the heat rating isn't a maximum temperature rating; its a stability rating/value de-rating point. Temperatures over that rating will equate in a reduction in value (uF) which is a majority of what you hear when your amp gets really hot.
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In the pro audio world the typical rule of thumb when it comes to electrolytics, temperature and life vs. re-capping is to generally replace with caps that have a higher temperature rating. Usually this is in tape machines and consoles like old Neve's and Harrisons that would run hot and eat caps like jelly beans. The consoles would also be left on 24-7 365 and those caps would last about 5-7 years before starting to fail on a semi-regular basis.

We'd pull out the stock 85C when they let out their goo and replace with 105C... usually panasonic's. In a console where there's 40-75 caps per channel times 40 channels... that's a lotta caps! And a lotta heat!

Getting back to it, of the biggest reasons to let gear warm up is that the sound DOES change in the early stages after power is applied. Most of the production gear makes strange sounds, tube preamps, EQs, mics... they'll clack and pop for the first 10 minutes or so and it takes a bit longer for the sound to 'stabilize'. I typically give that stuff at least 30 minutes to get going.

I've also met more then several 'old' amps that needed significant time on standby to really warm up otherwise they'd make all kinds of strange sounds. Get an old Marshall or Magnatone that wants 10 minutes on standby... they probably all wanted new caps too!
 
Re: Tube life and good tones

I don't mean to hyjack this thread, but related to hot tubes...

My amp is a Bogner Alchemist. Great sounding and versatile. Problem is, like was said earlier, it's one of those upside-down-tube amps. The chasis gets very hot from the tubes. So hot that after a couple hours of playing the chanel switching is affected...I can't change chanels either with the footswitch or the toggle switch on the face of the amp. If I let it cool down for a couple minutes, it works fine. (By the way, the tone sounds terrific when it's hot).

Is this problem directly related to one or more hot tubes, or is something else inside affected by the heat and screwing up the switching? And what is it that would be directly responsible? Is there anything I can do about it, other than mounting a fan inside (which I have done...and it works perfectly)?
 
Re: Tube life and good tones

I generally let my amp warm up on standby while I setup the guitar, strap, etc, etc. I haven't played it non-stop for a few hours in a long time so I can't remember if it gets better or not. But I do recall that everybody else at the local jam sessions were always turning their amps up the further we were into the night. Must of had something to do with the drinking and stuff.
 
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