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possibly a stupid question

4/30/2003 3:54 AM
andy	possibly a stupid question I'm concerned about the life of the tubes in my brand new fender blues jr. and I'm wondering if it's better to leave it on constantly (I don't pay for electricity at my apt, so that's not a concern) and maintain a constant temperature in the tubes, or should I be turning it off every night when I'm done playing?

4/30/2003 5:00 AM
jeff	Andy My guess is that this is your first tube amp... is that correct? Some people feel that tube amps are such a hassle, but they're really not. Just turn it off every time you're done using it. If you don't turn it up very loud, then your power tubes will last a very long time. If you're cranking it often, then they won't last quite as long. You'll probably never have to replace the pre-amp tubes...... See ya Jeff

4/30/2003 5:00 AM

jeff

Andy

My guess is that this is your first tube amp... is that correct? Some people feel that tube amps are such a hassle, but they're really not. Just turn it off every time you're done using it. If you don't turn it up very loud, then your power tubes will last a very long time. If you're cranking it often, then they won't last quite as long. You'll probably never have to replace the pre-amp tubes......

See ya
Jeff

4/30/2003 5:35 AM
andy	the simple answer to your question is yes. the more lengthy, informative answer is sort of. for several years I've had a stromberg-carlson model 220C hi-fi amp (from the 50's?) that I picked up from a friend for free. I started playing through it when I got bored with the dull sound of my crate GX-30 (no tubes). and just recently I've been able to afford a tube amp that was designed for guitar. while it sounds way better than the stromberg, that little hi-fi amp made me fall in love with the sound of tubes. that little amp was perfect for in my apartment, because even when it was cranked to max volume, it was still only about as loud as my crate at about 2. all it had was a clean sound (you could switch inputs and get more gain from an additional 2 stages of 6EU7, but it sounded like crap) which was ok for the time. the biggest reason I bought the blues jr. was that it was cheap, especially with the trade-in value I got for the crate. the added bonus is that I now have something to compare to when I build my own amp which is soon to come (I hope). the history lesson aside, I don't play it very loud, so you're probably right in that I'll most likely not have to replace the tubes for a very long time. on the other hand, I'd feel a lot better about it if it had a standby switch that I could turn off and leave the heaters on. after all, in my experience, elements of that type (whether they be tube heaters or light bulb filaments) tend to last longer if they are left on rather than turned on and off frequently, which was the overall basis for my question.

4/30/2003 5:35 AM

andy

the simple answer to your question is yes. the more lengthy, informative answer is sort of. for several years I've had a stromberg-carlson model 220C hi-fi amp (from the 50's?) that I picked up from a friend for free. I started playing through it when I got bored with the dull sound of my crate GX-30 (no tubes). and just recently I've been able to afford a tube amp that was designed for guitar. while it sounds way better than the stromberg, that little hi-fi amp made me fall in love with the sound of tubes. that little amp was perfect for in my apartment, because even when it was cranked to max volume, it was still only about as loud as my crate at about 2. all it had was a clean sound (you could switch inputs and get more gain from an additional 2 stages of 6EU7, but it sounded like crap) which was ok for the time. the biggest reason I bought the blues jr. was that it was cheap, especially with the trade-in value I got for the crate. the added bonus is that I now have something to compare to when I build my own amp which is soon to come (I hope). the history lesson aside, I don't play it very loud, so you're probably right in that I'll most likely not have to replace the tubes for a very long time. on the other hand, I'd feel a lot better about it if it had a standby switch that I could turn off and leave the heaters on. after all, in my experience, elements of that type (whether they be tube heaters or light bulb filaments) tend to last longer if they are left on rather than turned on and off frequently, which was the overall basis for my question.

4/30/2003 7:50 AM
jeff	I guess I'm just not worried about this in the same way. I mean, a couple of EL-84s is like $20. So, about every year (maybe less frequently) you might have to spend a few bucks, but compare that to something else. Let's look at strings for example: Let's say you replace strings everything couple of months on two guitars. So, let's say 12 packs of strings a year. Let's just say for simpliciy you spend $2 a pack. That would be $24. Looking at musiciansfriend.com they have a matched pair of Ruby EL-84s for $19.99. Now, do you wipe your guitar strings down after you play and whatever else to keep them in like-new condition? Well, that's enough rambling for now.... I hope I have not offended you because that is far from my intention -- I just wanted to give you a different side because I'm not as worried. See ya Jeff

4/30/2003 7:50 AM

jeff

I guess I'm just not worried about this in the same way. I mean, a couple of EL-84s is like $20. So, about every year (maybe less frequently) you might have to spend a few bucks, but compare that to something else. Let's look at strings for example: Let's say you replace strings everything couple of months on two guitars. So, let's say 12 packs of strings a year. Let's just say for simpliciy you spend $2 a pack. That would be $24. Looking at musiciansfriend.com they have a matched pair of Ruby EL-84s for $19.99. Now, do you wipe your guitar strings down after you play and whatever else to keep them in like-new condition? Well, that's enough rambling for now.... I hope I have not offended you because that is far from my intention -- I just wanted to give you a different side because I'm not as worried.

See ya
Jeff

4/30/2003 2:12 PM
John Culp	Standby and Tube Life It's well documented that tubes with oxide coatings on the cathodes, left at operating temperature with no emission current flowing, will lose emissivity and may not operate properly when taken off standby. There's a section in the RDH4 referring to that. It's discussed in Spangenberg's "Vacuum Tubes" and Chaffee's earlier "Thermionic Electron Tubes." The likely mechanism is that the actual electron emission from the oxide coatings comes from tiny islands of free barium metal in the oxide. Tubes don't put out full emission when they're first evacuated and fired up, it builds up during break-in. Current flowing through the oxides produces free barium (and perhaps strontium and calcium, depending on the mixture) metal. That's maintained in operation by the cathode current slowly electrolyzing the oxides. (End of life comes when electrolysis can no longer keep the cathode active and the emission falls too low for satisfactory operation. Tube designers of the 1930s shot for a 2000 hour life, same as for light bulbs.) Without current, evaporation of the metal into the vacuum (barium's the same stuff flashed into the getter coating when the newly pumped-out tube is baked out before sealing) and oxidation by residual gas traces in the tube ("cathode poisoning") deplete the active metal, and there's no emission when you need it. Oldtimers called this malady "sleeping sickness." So leaving an amp on standby, while unlikely to cause immediately discernable harm, is definitely not beneficial to tubes. The RDH4 recommends turning an amp off when it's going to be idle more than 10-15 minutes, IIRC. For keeping equipment on long term standby ready to fire up and go online in a hurry, the book recommended dropping the heater and plate voltages somewhat. (I don't have the book with me.) BTW, overheating the cathode with excessive heater voltage also ruins it. According to Chaffee, if the oxides get hot enough to sinter together (as in firing a ceramic), the emission will be drastically reduced and can't be restored. There's a good bit of margin above the operating voltage before that'll happen, though.

4/30/2003 2:12 PM

John Culp

Standby and Tube Life

It's well documented that tubes with oxide coatings on the cathodes, left at operating temperature with no emission current flowing, will lose emissivity and may not operate properly when taken off standby. There's a section in the RDH4 referring to that. It's discussed in Spangenberg's "Vacuum Tubes" and Chaffee's earlier "Thermionic Electron Tubes." The likely mechanism is that the actual electron emission from the oxide coatings comes from tiny islands of free barium metal in the oxide. Tubes don't put out full emission when they're first evacuated and fired up, it builds up during break-in. Current flowing through the oxides produces free barium (and perhaps strontium and calcium, depending on the mixture) metal. That's maintained in operation by the cathode current slowly electrolyzing the oxides. (End of life comes when electrolysis can no longer keep the cathode active and the emission falls too low for satisfactory operation. Tube designers of the 1930s shot for a 2000 hour life, same as for light bulbs.) Without current, evaporation of the metal into the vacuum (barium's the same stuff flashed into the getter coating when the newly pumped-out tube is baked out before sealing) and oxidation by residual gas traces in the tube ("cathode poisoning") deplete the active metal, and there's no emission when you need it. Oldtimers called this malady "sleeping sickness." So leaving an amp on standby, while unlikely to cause immediately discernable harm, is definitely not beneficial to tubes. The RDH4 recommends turning an amp off when it's going to be idle more than 10-15 minutes, IIRC. For keeping equipment on long term standby ready to fire up and go online in a hurry, the book recommended dropping the heater and plate voltages somewhat. (I don't have the book with me.)

BTW, overheating the cathode with excessive heater voltage also ruins it. According to Chaffee, if the oxides get hot enough to sinter together (as in firing a ceramic), the emission will be drastically reduced and can't be restored. There's a good bit of margin above the operating voltage before that'll happen, though.

4/30/2003 8:44 AM
Enzo	Re: possibly a stupid question Just turn it off. You can make cases for filament longevity and stuff but put them in context. I work on amps for a living, and I almost never see a tube fail because the heater quit. DArk tubes are more likely due to bad sockets. I replace maybe one tube in a couple years for filament failure. Your tubes will wear out for tone long before the heaters wear out. It just isn't an issue.

4/30/2003 8:44 AM

Enzo

Re: possibly a stupid question

Just turn it off. You can make cases for filament longevity and stuff but put them in context. I work on amps for a living, and I almost never see a tube fail because the heater quit. DArk tubes are more likely due to bad sockets. I replace maybe one tube in a couple years for filament failure. Your tubes will wear out for tone long before the heaters wear out. It just isn't an issue.

5/1/2003 2:58 AM
BillnShell	And.. Gweetings Sports Fans, All above is excellent. I'll throw one more idea out.. Whether it's free or not, leaving an amp on when not in use is ultimatly a waste of of a resource that took a time period and very unique set of circumstances to create that we cannot reproduce ( bang for buck, or otherwise ). Where I live, most of the power plants were re-configured to burn Natural Gas to produce electricity. While the benifit of cleaner air is nice, the fact is we are consuming something that, unlike oil which comes out of the ground slowly and thus provides a taper affect in regards to end of consumption, Natural Gas, being an actual gas, extracts quickly, thus it's end will be rapid and dramatic. Long story short, Let's not waste it too much, eh? I'm not an Eco-Nazi, I swear Bill

5/1/2003 2:58 AM

BillnShell

And..

Gweetings Sports Fans,

All above is excellent. I'll throw one more idea out.. Whether it's free or not, leaving an amp on when not in use is ultimatly a waste of of a resource that took a time period and very unique set of circumstances to create that we cannot reproduce ( bang for buck, or otherwise ). Where I live, most of the power plants were re-configured to burn Natural Gas to produce electricity. While the benifit of cleaner air is nice, the fact is we are consuming something that, unlike oil which comes out of the ground slowly and thus provides a taper affect in regards to end of consumption, Natural Gas, being an actual gas, extracts quickly, thus it's end will be rapid and dramatic.

Long story short, Let's not waste it too much, eh?

I'm not an Eco-Nazi, I swear

Bill

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