Burn in question and evaluation before burn in

I was a believer of burn in before, much more so now than before. When I started the thread two days ago, I noticed my new preamp turned from good sounding to intolerable after about 30 hours of playing. I played several my most familiar music, the treble was so bright and thin, and the bass was absent, that I had to check all my set up and connection to see if anything wrong; I found nothing and concluded the change in sound was most likely due to a certain burn in stage, I was not sure though, and hence posted my thread out of my curiosity.

After reading Albertporter's posts, and especially his prediction on burn in stages on transistor based design, I was more assured of that what I heard was not just my ears playing tricks on me.

After another 20 hours of play time since my first post, sure enough, the bass came back, and the treble became more focused and detailed. Actually, I found the bass is now actually a bit too much, I am hoping it would become slightly better controlled. Anyway, those are dramatic sonic changes in the last few days. I would easily dismissed the preamp if I only heard it during its worse burn in period.

Come to think of it, I seldom owned brand new equipment, and maybe that was one of the reason I did not experienced such dramatic burn in change before. Also, although the preamp was not totally new, the main board was replaced with brand new one, and that the unit I purchased came with brand new Linn silver interconnects and power cables, which I also put into use at the same time, all would attribute to more burn in changes.

If my current experience about burn in is jusitified, I would not judge a brand new equipment just because it does not sound good right out of box.

Maybe I'm not being clear? I agree wholeheartedly in burn in being significant overall. All I'm saying is that a sow seldom transforms itself into a goddess.

If my current experience about burn in is jusitified, I
would not judge a brand new equipment just because it does not sound good
right out of box.

That is exactly what the manufacturer and salesman would say. Just be patient -
eventually it will sound right. I prefer gear that sounds good from the "get go"
and barely changes with use - "robust" would be the right word or - perhaps -
"radio shack".

Burn in could certainly be conveniently used as an excuse by salesman or manufacturer when facing complaint about their product.

Re design with or without components with significant burn in drift, I do not have sufficient technical knowledge to decide which way is better, I am sure it is arguable. However, I think it would be very helpful for manufacturer to educate sales and the consumer how its products would change sonically after burn in. So for example, if I know a product would eventually be sounding brighter/darker than when it is brand new,then I have some fact to rely on in deciding if this equipment would be good for my system without keeping it forever, or well past the allowable return period.

On second thought, it is probably too much too hopeful for any manufacturer to do so. There is just so many variables, and there is no financial incentive.

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