Originally Posted by Von Soundcard /img/forum/go_quote.gif It's important when you buy tubes, if it lasts half the time you buy twice the tubes
I am mostly interested in old tubes ('40s-'50s), esp. military versions. That figure of 5000 hours sounds really good. However does it represent the time until they start to degrade their sound quality substantially OR the time until they fail completely ?
5,000 hours will last you almost 3 years, if you listen to it for 5 hours a day. That's a lot of listening.
Originally Posted by Von Soundcard /img/forum/go_quote.gif I am mostly interested in old tubes ('40s-'50s), esp. military versions. That figure of 5000 hours sounds really good. However does it represent the time until they start to degrade their sound quality substantially OR the time until they fail completely ?
In the absence of information about the circuit you are running them in, the 5000 hour figure doesn't mean anything. A tube life rating makes assumptions about how hard you are driving the tube. A circuit that is easy on the tubes can extend their life significantly. One that is hard on the tubes will chew them up and spit them out.
Originally Posted by Hirsch /img/forum/go_quote.gif In the absence of information about the circuit you are running them in, the 5000 hour figure doesn't mean anything. A tube life rating makes assumptions about how hard you are driving the tube. A circuit that is easy on the tubes can extend their life significantly. One that is hard on the tubes will chew them up and spit them out.
Very well said.
I will end up buying a duplicate of the tubes I like anyways, so if something DOES happen, I have another one handy. Or I'll buy in pairs, if I can.
Originally Posted by nick20 /img/forum/go_quote.gif Very well said.
I will end up buying a duplicate of the tubes I like anyways, so if something DOES happen, I have another one handy. Or I'll buy in pairs, if I can.
Concerning this:
To ensure good tube reliability you should probably run a tube at 70% or less of its maximum plate dissipation.
Using the general audio application of 250 plate volts, a bias of 8 volts resulting in 9ma of current and plate dissipation of 2.25 Watts, we find:
5692 - runs 43 % over maximum rating – It isn’t a 10,000 hour tube when you run it this HOT!
6SN7GT - runs 64% of maximum – coasting and liking it
6SN7GTA/GTB - runs 45% of maximum – Hardly turned on, may outlast you.
The older tubes probably burn faster then the newer type tubes.
Most jan or w designated tubes have 10.000 hours of life, minimum of at least 5000 anyway.
Originally Posted by tourmaline /img/forum/go_quote.gif Concerning this:
To ensure good tube reliability you should probably run a tube at 70% or less of its maximum plate dissipation.
Using the general audio application of 250 plate volts, a bias of 8 volts resulting in 9ma of current and plate dissipation of 2.25 Watts, we find:
5692 - runs 43 % over maximum rating – It isn’t a 10,000 hour tube when you run it this HOT!
6SN7GT - runs 64% of maximum – coasting and liking it
6SN7GTA/GTB - runs 45% of maximum – Hardly turned on, may outlast you.
The older tubes probably burn faster then the newer type tubes.
Most jan or w designated tubes have 10.000 hours of life, minimum of at least 5000 anyway.
I posted a link to that info.
I've read it before.
5692's are mostly for low watts, because it runs 43% over maximum rating. The normal rating for a 5692 is 1.075 watts, in order to "maintain" the 10,000 hour rating it must be used in low wattage amplifiers.
Most tubes will last you longer than a year, in which I recommend picking up a duplicate, just in case.
Originally Posted by nick20 /img/forum/go_quote.gif I posted a link to that info.
I've read it before.
5692's are mostly for low watts, because it runs 43% over maximum rating. The normal rating for a 5692 is 1.075 watts, in order to "maintain" the 10,000 hour rating it must be used in low wattage amplifiers.
Most tubes will last you longer than a year, in which I recommend picking up a duplicate, just in case.
-Nick
If they were only to last 1 year or more, i would suggest you get multiple duplicates. or do you change amps every year?!
Originally Posted by tourmaline /img/forum/go_quote.gif If they were only to last 1 year or more, i would suggest you get multiple duplicates. or do you change amps every year?!
I have duplicates, and a wide variety of tubes too. That I actually listen to.
Originally Posted by Hirsch /img/forum/go_quote.gif In the absence of information about the circuit you are running them in, the 5000 hour figure doesn't mean anything. A tube life rating makes assumptions about how hard you are driving the tube. A circuit that is easy on the tubes can extend their life significantly. One that is hard on the tubes will chew them up and spit them out.
I already said I was referring to operating conditions within the limits set by the manufacturer (current, voltage). If you have any specifics regarding what conditions can age faster (this type of) tube, by all means share them.
I now see a double figure of 10000 hours mentioned. This is already hard to belive, as new E88CC professional tubes have 10000 hours and they are among the best at this. Is there any resource on this ? And are these figures referring to operating life while sustaining the best sound or to the whole life-span until complete failure ?
Originally Posted by Von Soundcard /img/forum/go_quote.gif I already said I was referring to operating conditions within the limits set by the manufacturer (current, voltage). If you have any specifics regarding what conditions can age faster (this type of) tube, by all means share them.
I now see a double figure of 10000 hours mentioned. This is already hard to belive, as new E88CC professional tubes have 10000 hours and they are among the best at this. Is there any resource on this ? And are these figures referring to operating life while sustaining the best sound or to the whole life-span until complete failure ?
Well, I'll give this a try. These are the results that came up from a quick search.
"The 5692 is a commercial "premium" version of the type 6SN7 tube."
"They also have long life cathodes rated at 10,000 hours of service."
"The 5692 is a militarized version of the 6SN7, originally designed to work with artillery (all the vibration was destroying tubes at a frightening rate). Scott Frankland (the F in MFA) has written that they chose the 5692 because of its longevity (10,000 hours!!!)"
Then..
"5692 was markted as a 10,000 hour 6SN7, ruggardized for the military with multiple (usually five) support rods. But the reason why it lasts 10,000 hours is it was rated at only 275V and 1.75 watts of plate dissipation, much less then 6SN7 ratings. When 6SN7 electrical specs are applied, the 5692 doesn't last any longer then a 6SN7."
Yep, and I have many 5692's and do not like their sound. They have a poor frequency extension on both ends, lack dynamics and clarity and just plain do not present the music in a convincing manner. Now the 5691, the 6SL7 sub but at lower operating points, does sound pretty good but I will take a good Sylvania of 1952 vintage or a nice Tungsol 6SU7.
This tube is highly sought-after. BUT, it is NOT a 6SN7. It is an ECC32, which is NOT a drop-in replacement for 6SN7. As mentioned earlier, the current draw for this tube is 50% higher than a 6SN7. This will blow most power transformers over time. And power transformers rarely die alone – they usually take some other parts with them when departing this plane.
The higher current draw also results in higher gain – something which many people forget when trying out this tube. All other factors remaining constant, a higher gain results in a higher volume, which can in turn result in the (mistaken) impression that the tube has a ‘fuller’ sound.
Which may or may not have contributed to this particular tube’s much sought after status. Food for thought, indeed.
“It's interesting to note that a single dealer created virtually the whole myth and market for the CV181. He made a lot of bucks off them because he had an almost limitless South African source for the tube.” Robert H.
This section from the OP is interesting, but I think it can be slightly misleading. Certain designs , such as the SinglePower MPX3 and Extreme, are more than capable of handling the ECC32 and, in those amps, the ECC32 does in fact sound truly excellent, even in the opinion of the designer. The warning that the ECC32 is not a drop in replacement for the 6SN7 is very real and valid; the idea that in the right design that it isn't a good sounding tube (which was quoted by the OP) is most likely sour grapes about the fact that they are pricey. Just my opinion of course.
In general however, the OP is a terrific piece of work!
Originally Posted by Von Soundcard /img/forum/go_quote.gif If there is a good resource or anyone actually knows about this topic from experience and not Google, I'm still interested in this.
Also about factors which may shorten a 6SN7 tube's life, other than the obvious (excessive current / power).
What's wrong with Google? Do you want someone with a book to show you? Maybe copy pages and post them here.. I'm confused..
There's nothing wrong with Google, only with people that misuse it. Google is for (quick) finding, not for learning and certainly not for advising others. If you got your (professional) knowledge of Google I understand your position, but then do refrain from posting any more advice, at least for my questions.
Yes, I'd like someone with a book (what a scary thought...) or better yet with professional experience to give his opinions on the topic.
Originally Posted by Von Soundcard /img/forum/go_quote.gif There's nothing wrong with Google, only with people that misuse it. Google is for (quick) finding, not for learning and certainly not for advising others. If you got your (professional) knowledge of Google I understand your position, but than do refrain from posting any more advice, at least for my questions.
Yes, I'd like someone with a book (what a scary thought
) or better yet with professional experience to give his opinions on the topic.
I'll bite my tongue on this, before we head into OT territory.
However, most everything from Google, came from a book, eventually. How do you think it got there?
I'm working on a college degree, and 75% of the time I use Google, however I enjoy books to. Furthermore, I will guess there will be only a handful of people with tube books out there..
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