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In Reply to: Re: Leave the pre on all th time posted by Jim McShane on March 11, 2007 at 10:29:26:
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.
Follow Ups:
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.
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