My pre and power amps all have standby switches that provide a much reduced current to the tube filament, thus avoiding thermo shock when powering up from cold.
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I was under the impression vacuum tubes were akin to light bulbs so they shouldn't be on all the time. I keep my tube gear turned off and only turn them on when needed. My warm-up time is similar to Pops.
One thing I'm trying to help prolong tube life are various tube coolers and dampers. I'm new to tubes so I'm not sure this stuff will help. On my preamp tubes I've got Herbie's tube dampers. On my power tubes I have Pearl PCF tube coolers. They look like heat sink jacket when put around the tubes. They supposedly help with the heat. I just started with them so don't know yet if they are truly helping. This will be a long term test.
Well tube amps should never be left on unattended. Too many fires for a tube amp to just sit runnning all day long with no one watching it.
Tube preamps on the other hand can be left on 24/7 (usually)
I leave my four tube VAC Standard preamp on 24/7
As i am listening to music all day every day..
If all I listened to was on weekends.. I would turn it off betwwen listening sessions.
I only turn my tube equipment on when I going to be listening. A standby switch is nice if you have one (I do on one of my amps) but I would still turn it completely off if I wasn't going to listen a for a long time like for a day or two.
I would not turn an amp back on (like if you were changing cables or ?) for at least 5 minutes and probably give it a half hour and I wouldn't do it that often.
Another factor in how long tubes last is how hard the designer has chosen to run them.
When you get a new set of tubes I am a firm believer in NOT running them 24/7 or close to that just to speed up the breakin. I think best, for sound and longevity, is to run them 3-4 hrs then let them cool completely (4-6) then start up again. Do that for just the first week or so.
Jedinite24, tubes are similar to light bulbs in that in rush current is their main enemy. You will notice that most light bulbs blow out when turning on a light, that's in rush current.
Tubes will last longer if you avoid turning them on/off. Certainly some previous advice is solid. Do not leave tube amps on 24/7 unattended, and you can use stand by circuitry if your tube equipment employs it.
A comment: Light bulbs... IF you run a light bulb off a dimmer, and never run the light bulb at 100%, rather always at 50% or so..(and ramp it up slowly from zero to that 50% 70% etc. it will last nearly forever.
I would bet tubes which are very lightly stressed, like in some preamp designs will last for many many years.
(Some preamp designs which used 6dj8 s used to burn out tubes maddenly fast!!)
So how the tube cicuit is implemented matters a great deal for tube life.
I have read slightly under-biasing the output tubes will extend the life. Does it affect the sound? Yes in my opinion. That being said with most of my tubes I have to 'squint' to hear it. Another thing when the unit powers up you should let the tubes 'bias up' before playing music. I have found with under biasing the tubes it generally takes 2 to 3 min to bias up and when biased to spec it may take 5 - 7 min. Anyhow that's the routine I go through. My integrated is an Octave V70se which has standby and soft start. Soft start turns on the input and driver tubes first and about 20 sec later it turns on the output tubes.
thanks guys...I'm doing the same. Now how about this:
how do you know your tubes are beginning to fail and your music is suffering from tube deteriration? Do you bring you little babies to the tube Doctor to be tested? I would not know what to listen for. Also, when one of my driver tubes goes, time to replace all of them? I started a new thread on this to get some additional action. Thanks again.
Great follow up question, Warrenh. I'd wanted to get a tube tester and did talk do a couple of electronics techs with units for sale. Those discussions were not real helpful. They were very non-commital on whether a tester (and talking some of the better regarded vintage units...think Hickok) would do what I was hoping; i.e., warn of a tube going bad or that needed replacing. Kind of left me scratching my head and I never did invest in a primo tester as a result. I guess I could ask the audio dealer I've done business with to test them on his unit for a fee.
Hello Warren,I would have a new set of tubes on hand .You can compare the
sound quality between the old and new to give you an idea how worn your tubes
are.Also to get an idea what is changing as the tubes age.I ve noticed in guitar
amps that the sound gets duller,less vibrant as they age .Kind of like a set of
guitar strings getting old and flat sounding.You can also keep a set of old tubes
to remind you how much better your amp is sounding with the new,or newer
tubes.Ive noticed some of the worn tubes seem to lose some volume as well.
Since we're only talking about non-power tubes, then neither of your questions should be a source of worry. Leave the tubes powered 24/7 and change them at fixed intervals. It could be every 6 months or 2-3 years. A very small number of vendors are selling truly unused NOS tubes, most are used, even when stated otherwise. If you're not hearing any distortion or gain imbalances, then don't worry about it.
Generally, again reffering to light bulbs, tubes either are working or not working. You will hear failure as buzzing, becoming microphonic (hearing footfalls amplified), or some other audible clue. This is unlike cartridge wear, in my experiences. While a cartridge can slowly degrade over time, the tube's decline will be rather sudden. It will sound fine one day and then the next day you'll notice a buzz or hum being generated. Then you'll have to track it down to a specific tube.
Do you bring you little babies to the tube Doctor to be tested?
No, once an audible issue has been diagnosed in a tube, the doctor's equipment cannot save it, so why bother testing it?
Also, when one of my driver tubes goes, time to replace all of them?
You can, and many people do, but you don't have to. I would say it depends on the age of the tubes. If I've had the amp for 3-5 years, and one driver tube goes, I would probably replace them all. However, if the tubes are only a few months old, I would probably just replace the defective one. Again, think of light bulbs. Let's look at a chandelier, if one bulb goes, do you replace them all? I have a chandelier with 6 bulbs, recently 3 bulbs died within a 1 month span. I changed them one at a time. Should I have just changed all 6 at once, maybe. That's a personal issue that will depend on your own personal comfort level, OCD level and financial situation.
My Hickok 539C does have provisions for a "Life Test". This setting reduces the filament voltage by 10%. In this setting the mutual conductance is not supposed to drop more than 20% compared to the "normal" setting.
I'm no expert here, and can't confirm the accuracy, but it sounds like this is what you're looking for in a tester.
Thanks, Mark. Helpful info. The other thing I was hoping to be able to do was match tubes so if I had a group of, say, EL34s of the same brand but with different histories, be able to put together a quad that could be managed by my amp's auto-bias circuit. I believe if tubes are too mis-matched auto-bias can't compensate...apparently not good for the amp. Is matching something a tube-tester can be used for?? Happy to be corrected on this issue.
Warren - apologies for hijacking but hopefully this is at least somewhat related to your question; that is, having a reliable piece of test gear would keep you from unnecessarily tossing tubes that still have some life in 'em (assuming no audible degradation in sound quality).