Burn in question and evaluation before burn in

I think we are in full agreement about capacitors - see what Douglas Self has to say;

....well-known capacitor shortcomings such as dielectric absorption and series resistance, and perhaps the vulnerability of the dielectric film in electrolytics to reverse-biasing. No-one has yet shown how these imperfections could cause capacitor audibility in properly designed equipment.

The last sentence is a key one - "in properly designed equipment".

I think we also agree that it is not safe to assume that everything out there is designed properly and burn-in is necessary for many designs.

Cyclonicman,

My preamp was freshly installed with new upgraded board, it is supposedly better than the old version, but no, I have no idea how it will eventually sound.

Demo gear fully broken in and then decide if you like it. If you like it buy it...maybe even try it at home:)

what prompted me to ask the question was that I was frustrated that my new solid state preamp sounded good at first install, but became too bright, and strangely, the tight bass was gone too after a week.

Something is not right, IMHO. Check your interconnects and speaker wires. Any chance you got phase reversed - or did you flip the balanced/unbalanced switch or change the input volume offset by accident? Remote controls can be tricky - I have had weird things happen when I sat on one !

I think we also agree that it is not safe to assume that everything out there is designed properly and burn-in is necessary for many designs.

If that single criteria were used to assign quality to high end audio components, most or all of the best available would be termed "improperly designed," by that Douglas Self proclamation.

I'm excited by the improvements of the last few years from Dynaudio, Aesthetix, Audio Research, CAT, BAT and other companies that have embraced the latest high tech cap design. Many of the newest and finest pieces contain caps made by a guy that's a friend in the business. These caps are sold under a dozen names, made to different performance standards depending on budget.

I know of no contributions from Mr. Self that rival these designs, In fact he's probably one of those that think Radio Shack, Cardas and Nordost wire all sound the same with no audible effect on a high end system and the music it produces.

Wenrhuang, regarding break in process and what to expect. There are no set in stone results available where performance can be spelled out. Too much variation in parts and systems.

IF I had to guess (and this is a guess), considering the type of upgrade and the fact it's a transistor based design, I imagine right out of the box the sound was OK, but perhaps a bit compressed with slightly sloppy bass.

The music turned to shrill with poor bass after perhaps 20 to 50 hours and if it does prove to be superior to the original status (before your upgrade) it will not completely smooth out until about 450 to 600 hours.

You can accelerate the process by turning the preamp on and feeding it signal ( FM, CD, or whatever) 24 hours a day for a couple of weeks. That should be close to 400 hours by then.

The amps and speakers need not be on and no requirement to listen to music during this time unless you want to. I would love to hear a report if you choose to do this experiment. The electricity used will be less than the shipping cost to return the preamp and you might learn something.