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?
128x128jfrech
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 superpowercord...how 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...!!!
Ok...here 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.