Pavel, I suspect that you actually never tryied to do a real burn-in procedure, and it is difficult to judge about thing that was not experienced with.
Just make this adventure, put on the newly assembled and listened amp, for 1-2 days with dummy load, and listen to it after coming back from weekend.
Everybody who did it reported "wow".
I also used to use similar special CD, and I believe that there is nothing real with special kinds of signals on these CDs, it is more like advertising bla-bla.
Physics behind the burn-in is simple - at a non-zero temperature, micro-imperfections (point defects and their clusters) in solids undergo transformations, to thermally equilibrium state (concentrations and size distributions). The higher the temperature - the shorter equilibration period. At room temperatures these periods could be years and even centuries, depending on definite solids. Additional heating, high alternating currents, vibrations, ultra-sound waves induced i solids, facilitates equilibration processes, leading to orders of magnitude shortening of the periods of thermal equilibration (for instance, copper becomes softer, slightly better conducting, mechanical vibrations are changed).
Our task is in choosing most efficient additional stimulus for defects annealing, and square wave is better for me than special CD signal.
Interestingly, if you take that special CD signal, rip it to hard disk, then use an editing program to invert it back to front, you can return a burned in component to the non-burned in condition.
This is something that NASA doesn't like to talk about because it's controversial, but the early problems with the Hubble telescope were actually caused by them neglecting to burn in the wires.
This is something that NASA doesn't like to talk about because it's controversial, but the early problems with the Hubble telescope were actually caused by them neglecting to burn in the wires.
Something magical like burned resistor in Boucherot cell?
This is a bit another song. I am not referring to amps that become unstable under square wave signals, such amps have a lot of chances to vary sound signature stronger than the burning-in do.
If one uses a stable diy amp, reproducing square wave signal without stability problems, than simply increase power rating of the resistor in Boucherot cell.
If it is not a diy amp, simply decrease output power to resistive load.
Sure.
I have once destroyed even a polyester film capacitor during power amplifier square wave test. Output was running at some 40Vp-p or so, I was testing the capacitive load behavior. I forgot about maximum allowed dv/dt of the capacitor, and it exploded after about 5 minutes of testing
. Nothing nice, very bad fumes.
Please send me the test-recovery file data in *.wav, I'd like to try it as well.
For an even increased "wow" effect try whiskey "burned in" for 20 years or so...
I usually let a green amp run for 48 hrs before listening , interesting you run @ 80% for 24hrs I do agree break in is needed and essential on everything , annealing is suggested , what about compaction ..?
@Sy,
Are you serious about reversing procedure ...? If so then Wire direction after break in is very important ...
I do agree break in is needed and essential on everything , annealing is suggested , what about compaction ..? @Sy,
Are you serious about reversing procedure ...? If so then Wire direction after break in is very important ...
In my servicing career, I have observed an interesting initial burn in' effect, many times.
One of my amplifier standard servicing procedures (particularly for PA amplifiers) is to blanket resolder the power supply and output stages....this helps to ensure long term reliability, and reveals sub optimal solder joints that on first inspection would seem to be ok.
So, after this rework, my procedure is to power up via lamp and variac whilst checking DC conditions.
If all is good, I then reconnect to standard wall power, and allow thermal conditions to stabilise (lid on), whilst periodically checking and adjusting bias currents as required.
Usually, I will allow this no signal process to progress over four or more hours.
The next step is to audition the amp with known source, known programme material, and known speakers....ie my quite good quality reference bench system.
Initially listening is at low volume/power for extended period.
Then, I gradually raise the volume and listen closely.
The curious thing with fully reworked amplifiers that I have found repeatedly, is that at low levels, initially the sound is 'wrong', badly 'wrong' and this distortion gets worse as the volume is slowly raised, and reduces as the volume is decreased.
When a threshold is reached (first clip events ?), the amplifier/sound suddenly and dramatically changes for the better, and remains so, even after repeated volume changes, power up/down cycles, or fully cold restart.
This once only effect is perhaps not as stark as I have described, however a trained ear alerted to this behaviour will discern the sonic changes.
I expect that the likely explanation is that ferrous materials get demagnetised during the soldering process, and gentle clipping sets a magnetisation level in DC current path ferrous containing components.
Greater minds may have a proper explanation.
Dan.
One of my amplifier standard servicing procedures (particularly for PA amplifiers) is to blanket resolder the power supply and output stages....this helps to ensure long term reliability, and reveals sub optimal solder joints that on first inspection would seem to be ok.
So, after this rework, my procedure is to power up via lamp and variac whilst checking DC conditions.
If all is good, I then reconnect to standard wall power, and allow thermal conditions to stabilise (lid on), whilst periodically checking and adjusting bias currents as required.
Usually, I will allow this no signal process to progress over four or more hours.
The next step is to audition the amp with known source, known programme material, and known speakers....ie my quite good quality reference bench system.
Initially listening is at low volume/power for extended period.
Then, I gradually raise the volume and listen closely.
The curious thing with fully reworked amplifiers that I have found repeatedly, is that at low levels, initially the sound is 'wrong', badly 'wrong' and this distortion gets worse as the volume is slowly raised, and reduces as the volume is decreased.
When a threshold is reached (first clip events ?), the amplifier/sound suddenly and dramatically changes for the better, and remains so, even after repeated volume changes, power up/down cycles, or fully cold restart.
This once only effect is perhaps not as stark as I have described, however a trained ear alerted to this behaviour will discern the sonic changes.
I expect that the likely explanation is that ferrous materials get demagnetised during the soldering process, and gentle clipping sets a magnetisation level in DC current path ferrous containing components.
Greater minds may have a proper explanation.
Dan.
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it is just too suspicious that "burn in" is Always an Audible Improvement
not likely if it were objective materials property changes causing real electrical circuit performance changes - at least some changes could be expected to go the "wrong" way, stablize at a less optimal state after burn in
not likely if it were objective materials property changes causing real electrical circuit performance changes - at least some changes could be expected to go the "wrong" way, stablize at a less optimal state after burn in
Odd that you choose to bracket the word evidence as..... 'evidence'.
It appears you also question the validity of it. edit: (scientific validity)
jn
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