Running several tube amps for close to 30 years now I have sometimes replaced tubes early (few hundred hours) more often replaced them after a few years (thousand hours plus) sometimes even run till they died. Almost always it seemed if they degraded at all it was way too slight and slow to notice. Trying new tubes hoping to improve the sound almost always is a total waste of time. Its not that there aren’t differences. Its that the differences are too slight to bother with. And I will bother with an awful lot of really minor stuff. But the difference between tubes, its a crapshoot but in general there is less difference between tubes than between the same tube new out of the box and after running a few hours. The best tube of all I have tried is the JJ, which is also the cheapest. Tube rolling, hoping for some sort of transformatory revelation, is just nuts.
Unless you spent $1300 for your 300-B. Those of course are totally worth it. Eyeroll.
Small signal tube life, (example 12AX7 and 12AT7), for new production tubes is about 4000 hours average. NOS signal tubes from the 1950s, 1960s are said to average up to 10,000 hours of life.
The average tube life depends on how hard the designer of the amp pushes the tube in the circuit design.
New signal tubes as a rule gradually wear out slowly over time.
Trying new tubes hoping to improve the sound almost always is a total
waste of time. Its not that there aren’t differences. Its that the
differences are too slight to bother with.
Guess I've had difference experiences than you with swapping tubes, for me there have been noticeable differences whether signal or power tubes.
@jrod68H@jrod68Ha@jrod68H@jrod68H link to Brent Jessee's website (I'm only a customer) but he provides listening impressions to various brands within the specific tube type - might be helpful to you
Thanks for the comments (so far). I can't tell you how much I'm enjoying my McIntosh MA252 with the Maggie 1.7s.
Darn millercarbon , you can't say stuff I agree with. It is not fair:)
Likely gradual unless a tube starts going bad. You will know when that happens. Most hybrid amps have tubes in the input (which last a long time) and solid state outputs. Check out Brent Jesse or Upscale Audio for tube options. I would wait a while before jumping into other tubes, so you can establish a baseline that would make it easier to identify the characteristics of the other tubes.
Darn millercarbon , you can't say stuff I agree with. It is not fair:)
Nor is it easy. What I mean is, tubes vary so much from brand to brand and even tube to tube its very hard to say anything meaningful about them without someone else being able to say something completely different- and both of you be right!
I mean, I used to think tubes were really reliable as maybe only one of probably 30 or 40 had ever really failed on me. Then in short order I had two flare out quite dramatically- and one of them was brand new!
There really is hardly any difference between tubes, not only between brands but even between certain types. KT88 is better to me than 6550C but not by much. JJ is better than Svetlana but by even less. But I'm comparing relative to something like a $150 Quantum Fuse or $60 set of BDR Cones or even something like running a demagnetizing track through your system. Those range from 3 to 10 times more important than the difference between tubes, which to me makes buying a new set when you already have a set a waste of money. But another guy might think a barely noticeable improvement for $500 is the moon and the stars. So both can be right and it is darn hard to say without being set up either way to get skewered.
So good to know. Thanks.
Since that’s a hybrid amp, I don’t feel you’ll notice the signal tubes degrade as much.
If it was a complete tube amp, with power tubes, you’d notice a big difference when they degrade.
I have an old sansui tube amp. When those 7591 power tubes start to go, you really notice. When you replace them it’s like you have a brand new amp. I’d tube roll your signal tubes because their is quite a difference in the sonic signature of those tubes. It’s also a lot of fun. Glad you’re enjoying your new setup.
I have a Conrad Johnson PV2ar preamp (bought new in 1981), solid state Hafler 100W amp going through Anti-cables to '78 Klipschorns.
Due to the high efficiency of the K-horns, when tubes start to age I can hear it easily....sounds to me like "wind" noise.
When the sound of the wind, sometimes a hum, gets obtrusive I know it's time for a tube change.
Brent Jesse has been my supplier for a number of years now and his advice has always been spot-on regarding the sound of NOS replacement tubes.
In my case there is a noticeable sound difference between tubes.....nothing overly dramatic, just a sweet richness that varies from brand to brand.
If your system isn't overly sensitive, and the audible tube sound differences are negligible, I would say it doesn't matter...... why spend the extra money on rare tubes?
Right now my only tube piece is my phono amp which uses 6922s.
What I care about most is noise. Roger Modjeski's Tube Audio Store tests all their tubes and hand selects them. They then sell them in grades. Their Super Low Noise 6922s were embarrassingly quieter than the stock tubes from ARC. I keep the thing on continuously. The tubes are 6 years old and as far as I can tell going strong. I have a spare set of tubes just in case something happens so I will let the working tubes go as far a they can. If you have a tube unit do check Roger's site. Every tube he sent me is dead quiet. The SLN tubes are more expensive and worth every penny.
I did a lot of auditioning of both low level tubes and power tubes in preamp, power amp and phono stage, and found that there was no reliable general rule - some brands sounded better in one use and another in a different use. It is cheap to try some of the tubes so I bought two or three different ones just to see what was what and used the ones I preferred (based on blind listening by myself and another person).
Auditioning power output tubes could get pretty expensive, though....
Tube life in most gear is quite good - and in some applications they seem to last forever without deterioration. In phono stages, for instance, you'd have to be a vinyl nut that played for hours every day to age out the tubes in a decade.
As was stated, though, it does depend on the amp design and how highly 'stressed' a tube may be in a given application - push the voltage and shorten the life.
I once owned an all-tube phono preamp (Icon) and only gradually noticed its sound no longer seemed up to snuff. New tubes changed that dramatically. BTW, the mfg. admitted the tubes were driven hard in that application.
As far as tube changes making little difference, I have to emphatically disagree. Changing out KT-88s for KT-150s in my Primaluna Integrated some years ago gave terrific power but dramatically sacrificed timbre. New preamp tubes in that same amp turned the sound so crisp I sold them nearly immediately (failing to let them break in, alas). More recently, in a Vincent tube integrated amp, I could not get the highs in my rather live room to settle down. New tubes not only retained the high-end and made it more natural, they also dramatically filled out the bass. None of these sonic changes were even subtle!