Do new tubes undergo break-in like other devices?

I just put a new pair of Mullard Ecc34 (should be 6sn7s) tubes in the r/l inputs on my BAT VK60. These are the 2 most importants positions for BAT amps.

Part of it sounds wonderful...back of the soundstage, instrument separation, dynamics, articulation in the bass. Oh, and much queiter.

However, I don't think they have as much gain, I have to turn up the volume some on the preamp, and the bass is much lower vs the other parts. Kind of like a new power cord...needs time to open up. I can deal with the gain, not sure about the bass. This may just be a system matching thing, works great for some, not for me.

Is it break-in related?
Can be, I know I would give 50/100hrs burn in time before I would really find fault here. Then it could be matching. I assume you have checked bias( I am not all that familiar with how to set up a BAT) as it could have changed. That being said, I know I can change the sound of my tube devices by changing out a couple of tubes. Like most things, it part of the reason that there are so amny out there.
Yes. Tubes do burn in. We find anywhere from 25-100 hours depending on the type of tube and the equipment used. Some gear draws a lot more current which tends to break them in quicker than low voltage devices.
the vast part of break-in process of the new tubes is when you idle them for almost two hours with no input signal. the second and further times you will have to follow the instructions suggested by manufacturer on how long you should worm-up the tubes before you listen. the rest will come with time. i might mistake to say that it's more matter of personal adaptation rather than some physical electronic process takes place, but imho i can't find any other explaination.
Man!!!! I asked the same question and got different answers!!!!

I recommend that you listen like crazy for the rest of your life. You lose your hearing by the day, anyway. Worry about there not being enough broken-in musicians.

Brad Day
Atlanta, GA
Jfrech, did you change from well used Russian tubes?

If so, consider two points. The Russian tube had poor highs when new and undoubtedly got worse as it aged. Second, the bass on Sovteks (if that's what it was) are "bumpy" in the bass.

Comments already posted about tube break-in are accurate in my experience. If you are still dissatisfied after your gear has settled in, post back here.
I was using some early russian 6sn7's bought from upscale audio. The positively smoked the stock sovteks from the start. I do have about 1.5 years on the russians...

Sounds like a little patience is in order here. Thanks for the info!
I've found tubes need break-in but not to the extent of components such as amps, cables and speakers. Tubes go through the same sonic character changes during break-in as other components, but I've found they do so much faster.
A new power cord needs time to open up?????!!

What does this mean? How does it open up? I didn't know powercords "opened up"...

I'm not going to a DBT zone or saying wires don't matter. I just want to know what to listen for if I buy a long I should wait for it to open up before I decide that it didn't matter.

Do wall outlets need time to "open up" too?
everything "opens up" and breaks-in. this crazyness goes onto the tip-toes and other tweaks. man, your stand should also break-in...

listen more more more more to realize he...he...!!! is what I heard...less than 30 hours on the tubes...

These are awesome sounding, and in the right system, you'll love em. If you are looking for more air, detail, quietness, these will do it for you. The bass was a little less for me, and that's a weak point in my system before the tubes went in. A single VK60 is a little underpowered for my room size and WP 6's.

Everything else I loved. The bass was more detailed, more tuneful, just less of it.
Tubes do not break in, they break down. There are only a finite number of electrons available to make the leap. So, as the thoriated coatings become thinner (even after hours, not just weeks or months) the tube's performance can only become worse. Any improvement that one may hear can only be related to the piece reaching its thermal equalibrium. No piece of audio gear performs fully or properly before all of their conductive components normalize their temperature. Of course, this is just warm up not break in. This gradual decline of a tube's performance is just a way that we pay the price of their greater musicality.
here is my conclusion...

tubes do not break-in they start to work out their life time just from the moment you turn your amp(s) on. within the time to the end of tube life tubes sound dull and mushy and certainly need to be replaced.

next thing you do is you change tubz and certainly you need some time to adopt to them since they do sound different from your previous setup and certainly brighter. within "n" hours you will get used to it.
Dozer, yes, wall outlets open up. I had an FIM 880 that started out OK for my system, but got progressively brighter over the course of 4 or 5 weeks. I finally had to take it out. I sold it to my buddy with a tube system and he loves it.

Also, power cords do break-in as well, but usually faster than other components.
Astonishing that you could attribute the brightness in your system to a wall outlet that had gradually broken in. My hat's off to your aural acuity and deductive powers. Well done... For me probably wouldn't help because darn if I can't keep the rest of the environment exactly the same week-to-week... I'd never think to switch out my wall outlet for tone control.
An ECC34 has different specs than a 6SN7. That may be causing the difference, although I have read that it will substitute.