Burn in question and evaluation before burn in


We all experienced sound transformation before and after a new equipment or cable is burned in, however, I am wondering if there is a general rule as to which direction any burn in would be heading? Specifically, I am interested to know would sound generally go smoother/darker or brighter/more transparent after burn in? I am thinking if there is such a rule, it would be valuable to know for evaluating products.
wenrhuang
For those of you wondering about the effects of both better caps AND burn-in, I propose a simple and low cost test:

1) Buy an inexpensive but decent quality tube amp in its stock configuration. My example will be the Almarro A205A. Low power but very nice sound, even stock.

2) Listen to your reference recordings and get the amps strengths and weaknesses firmly in your auditory mind, as best you can.

2) Change the cheap output caps for something nicer. I put in Sonicap Platinums; lots of people use V-Caps, sometimes Mundorf, pick your flavor. Make no other modifications to the amp. Doing this yourself is usually pretty easy and keeps the cost down.

3) Put the amp back in your system and fire it up, no prep, no burn-in.

4) Put your reference recordings back on and listen to them again, once again noting the strengths and weaknesses.

5) Listen to the reference recordings again at 50, 100, 200 and 400 hours. Feel free to accelerate the burn-in by leaving the equipment on 24/7 until it reaches the hour checkpoints.

I predict that during 4) you'll hear immediate and noticeable improvement in many areas. This often the case even with far more expensive amps, because so many use parts that aren't very good. This has little to with good design or bad design; it's mostly about hitting a price point. If that isn't convincing that better caps are generally an improvement, I'm not sure what else will.

I further predict that at the checkpoints in 5) you'll hear noticeable differences, some that will be improvements, some that won't be, but that at all the checkpoints the sound will be converging on what you hear at 400 hours. The total number of hours to "settle in" will, of course, vary with the equipment and the caps, but you get the picture.

At 400 (or whatever your "settled in" point is), I predict you'll think the sound is improved, possibly greatly improved, from what you heard immediately after the upgrade. If that isn't convincing that burn-in is real and generally an improvement, I'm not sure what else will.

If you only bought the amp for the experiment and not to keep, chances are good you'll be able to re-sell it for $50-100 more than you paid for it, because lots of people believe doing such upgrades makes a difference and are will to pay for a piece where they're already done and burnt-in. At worst, you'll sell it for what you paid for it and the only cost of the experiment will be the caps and maybe some shipping.

I was skeptical about both better caps and burn-in effects until I did the above experiment. I am no longer a skeptic.

David
My example will be the Almarro A205A. Low power but
very nice sound, even stock.

The total number of hours to "settle in" will,
of course, vary with the equipment and the caps, but you get the picture.

Exactly! I completely agree. Those tubes and that coupling capacitor on the
Almarro will almost certainly yield audible changes with a re-cap or burn-in - I
can see that simply from a circuit diagram. This is exactly the kind of design
that I was referring too - one that will indeed change audibly pretty much over
its entire useful life - although there should be a period of 1000 hours or so
where it is fairly stable.
Shadorne,

I'm glad we agree. :-)

I think the question then becomes, is it even possible to build an amp that is unaffected by component burn-in? My experience, and not just with the Almarro, leads me to believe that it's difficult, maybe impossible. Do you own such a piece, or have an example you know of? Do you think such pieces inherently sound better than ones that experience burn-in, or do they just drive you less crazy because they don't change?

David
The discussion is veering towards the absurd. Are people seriously arguing that they can accurately compare the changes in the sound of high quality systems when separated by hundreds of hours of actual listening time? It can't be done. Memory is not that reliable. If a component takes 400 hours to fully settle in, that translates to 2 or 3 calendar months (assuming 3 or 4 hours/day of listening). There are too many variables involved for any reliable comparative conclusions to be drawn over such a time span.