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timm

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What is your typical tube life for a pre? reason I ask.... I was looking at a tube pre - and asking questions about age etc... and the seller kind of kept forgetting to answer on the age... So, I'm going to steer clear of it... Here is just an example 'How old is it?' answer: 'I am the second owner... the first owner had it a month.' ...okkkkkk....second question: 'So, how long have you had it?' answer: 'I got it in march'...Usually a year here would be helpful??? So, I go and look up and the guy bought a pre in march...of 07!!!... Jeez I hate that... Anyway, enough for your amusement...

When you replace - and if you needed 4 - would you replace all 4 at one time - if you were getting the same tube? thanks all....
 
Just put a new set of 6H30s in my ACT 2 before I sold it. Got about 14 thousand hours on the last set, so I was pretty surprised.

Depends on your preamp, how hard it is on tubes and what tubes you use. One of the best things about good NOS tubes is that they were usually made more robustly. Where the Chinese and Russian tubes can go in 3-5000 hours, a lot of the Telefunkens, Mullards, etc. would often go 20,000.

Unfortunately no hard and fast rule. All the big tube heads I know have told me that if tubes don't croak at turn on, the big milestones are 100 and 1000 hours. Typically, everything I've had here has failed at that point or gone on to a fairly ripe old age.

In a preamp, unless you know that the gain measurements, etc are all similar (or really close) I'd replace the whole set.

Another thought is the next time you buy tubes for your preamp and purchase a matched set, ask them to match two spares for you. That way if a tube goes south along the way, you have a similar one to plug in, costing less money in the long run.
 
thanks jeff -- so they are different based on their batch too - not just the horus on them? Your comment about buying a couple of spares -- Are you saying the match is really about when and how they were manufactured - not necessarily about the life on each? so, if 2 were purchased at the same time - yet one of them was being used while one was in a box, just replacing the 'bad' one would be 'ok'...?
 
Tubes in most pres last a long time 5 years (10-12K hrs) or so has been my experience with both of two Counterpoints and my current TAD. Besides, pre-amp tubes are not too expensive even if you replace them more often.
 
I agree. The tubes used in pre-amps are low-voltage signal tubes and should last between 10k - 20k hours. That is true for most tube-based pre-amps, unless you stumble on a unit which drives the tubes very hard. Case in point is the Audible Illusions Modulus 3A which has a reputation for being a "tube eater"! Great sounding pre-amp, but the tubes only last around 2000 hours in these units. Consider yourself...warned on the subject of tube life.

I usually replace the set in an attempt to match the output voltage of the left and right channels. Think of it as replacing a pair of shoes when 1 is worn out ;)

Spike
 

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