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In Reply to: Tubes - on or off? posted by w9ls on March 11, 2007 at 01:11:50:
The tubes in it should go thousands of hours before problems. Pre's
tend to run tubes far below their max operating characteristics
(Audible Illusions are one exception) so they tend to last longer than expected.
You'll want to leave it up if possible to lessen warm up time
which with some pre's is a few hours before they thermally stabilize and sound
their best. If you're using shockingly expensive tubes in the
pre you may want to shut it down if you're away for days, but I've found tubes
are kind of like light bulbs, you get more hours out of them if you run them constantly.
Others may have a different opinion or experience.If your SS amps have a standby mode that helps
shorten their warm-up as well.
Follow Ups:
One year (365 days) x 24 hours is 8760 hours. With the pre on continuously that will use up the tube set in a year or less. The people I know who buy tubes from me that leave their pre's on all the time change tubes about every 6 months.To each their own, but that seems like a terrible waste to me.
As well, capacitors wear as do some other components. And the electricity use is much higher than it needs to be.
I use Black Gates in most power supplies, and as we've noted
from previous threads, they sound best after a day or two of being left
on. Sorry to be obtuse Jim.Preamps using other power supply capacitors may warm up and sound
fine after a half hour or so. Previously, I had good luck
with preamps after only an hour of warm up. w91s's post would be best
answered by his own experience, but satisfactory results can
be obtained with minimal warm up, he should power down if it
also best suits his interests.
Jim,
I thought most small signal tubes, such as 6922 and 12Ax7,can burn for 5 years with no trouble when used properly in a DAC or pre amp. Also FWIW, some manufacturers put the power switch in the back of the pre-amp or DAC because it is their intention that you turn it on and leave it on. Just a thought.I wonder if there is some sort of data table available that gives us MTBF figures for tubes like similar data we can obtain for transistors.
Mullard used to make premium quality tubes they called "10,000 Hour" tubes. That might give you some perspective on anticipated life.To say the tubes can last 5 years is a lot different than saying the unit can run continuously for 5 years - which is 45,000 hours or so.
Putting the power switch in the back is sometimes done because it reduces the amount of AC carrying wiring in the unit, potentially reducing noise/hum. I am not aware of any tube pre or DAC maker that recommends it be on all the time - although I'm sure I don't know EVERY one made...
There is some MTBF data out there, I've seen it, but how relevant it is (or where to find it!) I'm not sure of.
Hi Jim,
Glad to see some sanity on this issue. I am not an Al Gore type, but it is an awfull waste of equipment and energy to leave audio equipment 24/7. Glad we can turn on our rebuilt Citations and get excellent sound after a brief warm up, some of mine has tubes that have been in use well over thirty years with thousands of off/on cycles. If left on continously the tubes would have been history back in the sixties.
I didn't know they only lasted 10,000 hours. I will keep that in mind.FWIW, the owner's manual for my Audio Note DAC recommends that I turn it on and leave it on. They say that the tubes will last just as long leaving them on as if they are cycled on and off. I believe there are other reasons why they recommend this too. Like keeping the Blackgates on continuous burn in because they sound better that way.
Anyway, thanks for the info about the Mullard premium tube life. It is helpful.
Especially if using rare, NOS tubes.
3 to 4 years tube life is common in my experience, even ratty old
used up Bugle Boys last more than a year. That's in a cross section
of preamps as well.I'm sure some preamps run tubes hotter, but even if the number is
more like 2 years it's harldy that big a deal compared to other
costs in hifi. If a preamp burns through a set of tubes in 6 months
it's time to get a different preamp.
Granted, I do turn things off, but mine have been playing away for at least 10 years and were used to begin with -- found them in an estate sale Tandberg tape deck.
Teles are the tubes for longevity. I pulled an early-60's Tektronix 531 scope apart, with loads of 6dj8s, 12aus, and 12axs. All the original 12au's (other than a pair of Teles) had been replaced with orange-globe Amperexes, and were all past their best. The two Teles were obviously originals, and still pegged the top of the meter.
Dave if the average life of the Telefunken ECC83/12AX7 is 10,000 hours it is very possible they could last 10 years.Just an example:
Say on average Mon thru Fri you listen to your system a couple of hrs a day. On weekends a total of 10 hrs. That would be on average of 1,040 hrs a year.
Your premise is logical, but a little off in my case. Especially since I retired (in 2000), the system has been on for a LOT more than a couple of hours a day :-)
Dave,I do get worn out ones from time to time. But I will say they are amazingly durable! Way more so than any other I've seen.
Just bear in mind that long after Telefunken stopped producing these tubes they kept ordering them in Yugoslavia. These tube have perfect Telefunken marking but in fact they are the same Ei tubes.
When I get home from work, I turn on the pre. I use about $1,000.00 of NOS tubes in that unit. In a half hour it is completely warmed up. I turn it off before bed. Why should I run those tubes for a completely non-essential additional 18 hours a day?? The tubes will last 3-4 times as long--fact.
That's my thinking too. No matter how long the tubes last with the unit on all the time they will last longer if the unit is off when not in use. Those cathodes have a finite number of electrons to give off. I'm of the school of thought that says I want them to work for me when they boil off the cathode, not just warm the unit up.
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