Now directly from the mouth of an engineer designer who i trust more than mijostyn bashing audiophiles as all deluded by their brain 😁:
«First and foremost, I’m an Engineer and don’t do mojo BS. The fact this Industry has become a marketing nightmare of BS and lies not only misleads people, but attempts to fill knowledge blanks with marketing instead of fact. Add to that a billion unqualified people on the internet all with an opinion. If I can’t measure it or analyze it, it ain’t happening. Emotive response based on gut feeling is completely unreliable when attempting to address something like this subject. Often what sounds ’better’ is simply a result of you playing in a way you perceive as ’better’ so something external to you must have changed, right ?
So for this discussion, while its impossible to completely remove ones own tonal preference, the end result should be thought of as reliable unit operating within its design parameters.
However........
Yes, I can certainly vouch for the fact that amps do break in. They start off a long way from their intended operating points. Its a rather exponential process. No newly built amps sound incredible on first fire up, I’ve built a few thousand so can say this with a lot of confidence. Almost every component ’breaks in’ to some degree or other. For some components, its not so much a break in, more a settling at a particular operating point or range. Tubes certainly do initially burn off contaminants on the cathode coating and on other structures, even contaminants in the gas itself (every fired a brand new power tube and heard some crackling that goes away after several minutes or an hour or two) . It also takes a little while before their bias will remain stable. Preamp tubes as well as power tubes. Electrolytic capacitors form an oxide layer on the plates over time. There’s a period of about 30 mins to 2 hours where you can see the ripple levels change on a scope as they start to operate more efficiently. Their ESR also decreases in the same time period. The electrical and magnetic properties of transformers change too, but that’s more long term. This process continues, eventually flat lines and then starts to reverse as some component starts to reach the end of its working life, usually power tubes are the first to degrade.
The break in testing is as much to insure against premature failure as it is to ’make the amp sound and feel right’. However, there is a marked change between hours 0 and 1 and hours 1 and 5, the noticeability of the change gets less and less after longer periods of time. Noise levels do also generally decrease, but not always, they can in fact increase in some cases.
I wont even start to tweak or change anything once I’ve got an amp up and running properly, until its been hot run for a couple of hours. Its pointless as any change you make is countered by all the other parts settling in to their operating environment.
Speakers are an electro-mechanical device, so they certainly break in. Some people use variacs to attempt to speed this process up. Personally I think you are better just giving them the complete signal range by simply playing through them in the way you intend to use them and putting up with about 20 hours of stiffness.
Outside of this, the most major factor to changing tone on a day to day basis are changes in wall voltages, temperature and humidity. All these factors affect the operating points due to resistive, capacitive and inductive changes and the fact that every component has a tolerance band. I developed the autobias system to counter some of the major factors that change the tone of your rig from club to club due to bias shift caused by changing voltages.
Just a word of warning on buying ’burned in’ tubes. If by burn in they mean fired up with the filaments heated for 48 hours, that’s not really doing anything apart from creating a nice orange glow and giving them an excuse to take an extra $5 from you. To settle in a tube (for me) has to be done in its end operating environment. Granted, a few hours under load by the Supplier on a test rig will certainly help find early failures, but they will still need to ’settle in’ in your amp.
So, its all very real and physics can 100% back it up. Now heres the big caveat that separates science from Mojo.....BREAK IN DOESN’T ALWAYS GO IN A POSITIVE OR PLEASING DIRECTION. Think about it, that would be impossible. You certainly can get an amp that sounds great after two hours and by hour five has settled in to a less than ideal place and requires reworking. This is the reason I gig test every amp. Some things I may only notice when its being used in a live setting. However, the general direction of the settling in period usually leads to a more stable place and closer to the actual intended design points. Hope that helps.»
https://www.thegearpage.net/board/index.php?threads/is-it-possible-for-electrolytic-caps-to-break-in-burn-in.1671283/
