What are the various opinions (there always seem to be various conflicting opinions around here) regarding the early burn-in, if at all, of a new build or significant re-build (outputs) of an amp? Should I leave on for a day or two? Cycle several times? How long before I pull the test speakers off and connect some "real" ones?
In commercial products burning in is done to check for early failures (see for example, Bryston).
At which point you disconnect the speakers is up to you; personally I use a DC-protection, so I don't have to worry too much about this. Certainly a little sinewave testing helps otherwise also.
Have fun, Hannes
At which point you disconnect the speakers is up to you; personally I use a DC-protection, so I don't have to worry too much about this. Certainly a little sinewave testing helps otherwise also.
Have fun, Hannes
If you're worried about an early failure, I'd thermally cycle the output transistors several times (work the amp hard and then shut it off until it's cold and repeat). And I second DC protection being a good idea regardless.
If you're talking about the other kind of "burn in" favored by audiophiles for improving the sound quality, I wouldn't worry about it too much. While electrolytic capacitors have been shown to slightly improve their characteristics after some use, there's no real evidence transistors improve with more hours of use.
If you're talking about the other kind of "burn in" favored by audiophiles for improving the sound quality, I wouldn't worry about it too much. While electrolytic capacitors have been shown to slightly improve their characteristics after some use, there's no real evidence transistors improve with more hours of use.
I'm mostly concerned about the possibility of early failure due to component failure or quality of assembly. For a receiver (ie Marantz 2285B) with some type of internal speaker relay, should I still have something between the outputs and the speakers? Will this really catch output failure in time to prevent speaker damage? Why don't high end speakers already have something like this, seems a pair of $3000 speakers would come with some type of self-protection.
Depends on the protection
Of course it will if the protection deserves its name.
Pro gear has usually a large elco in series to the amp; belt and suspenders way of protection in the pro-world (means both the amp and the speaker has built-in DC-protection).
I guess a large elco does not sell in the hi-fi world.
Have fun, Hannes
Unfortunately, most speaker protection circuits either need power to operate (something speakers don't usually have) or they degrade the sound. Even fuses degrade the sound and don't offer much protection unless they're sized so small they tend to blow during regular use.
So the best place to protect speakers is in the amp/receiver. And most commercial products, with the notable exception of lots of high-end products and a few others, have at least DC protection with a speaker relay. If your Marantz has a delayed turn on relay for the speakers it very likely already has DC protection. So no worries.
I read a story about an engineer (working for a manufacture) trying to determine just how fast the protection needed to be to save a speaker. So they simulated a failure of a 100 watt amplifier and the woofer literally caught fire in under a second with 40+ volts of DC applied. Their conclusion was "the faster the better". Which is to say fuses are often too slow when sized to meet other demands.
So the best place to protect speakers is in the amp/receiver. And most commercial products, with the notable exception of lots of high-end products and a few others, have at least DC protection with a speaker relay. If your Marantz has a delayed turn on relay for the speakers it very likely already has DC protection. So no worries.
I read a story about an engineer (working for a manufacture) trying to determine just how fast the protection needed to be to save a speaker. So they simulated a failure of a 100 watt amplifier and the woofer literally caught fire in under a second with 40+ volts of DC applied. Their conclusion was "the faster the better". Which is to say fuses are often too slow when sized to meet other demands.
Yeah, based on what I've seen 500mS is risking damage and even flames 
Microcontrollers let you do some fun things, but they're not as failsafe as a simple analog circuit and they also create lots of RFI hash that can find it's way into the amplifier where it either directly causes noise or gets demodulated and causes problems.
Microcontrollers let you do some fun things, but they're not as failsafe as a simple analog circuit and they also create lots of RFI hash that can find it's way into the amplifier where it either directly causes noise or gets demodulated and causes problems.
RocketScientist said:Yeah, based on what I've seen 500mS is risking damage and even flames
I decouple the PIC well and use the internal RC oscilator which runs quite slowly.
Once you have a micro in there you open up all sorts of possibilities.
Hi,
for semiconductors the failure will be in the first few hours or after many thousands of hours.
Normal measuring and testing and setting up and monitoring of output offset and bias currents usually gets you past the first few hours. No additional burn-in required.
Polarised capacitors rely on a chemical reaction in the plates/electrolyte to perform to specification.
This may be why some talk of burn-in improving the sound. basically they are comparing the final sound with in-spec or near in-spec capacitors to a system running with capacitors well out of specification.
This is very easily overcome. Don't listen to polarised capacitors that are out of spec.
Pre-condition all electrolytic capacitors by ultra slow charging them to max Vdc just like the manufacturers do before they measure them and publish the results.
This pre-conditioning reduces the leakage current without damaging any of the foil in the plates.
You can do all your 50V caps with a separate 100k feeding each one. Then do your batch of 63v caps. if you have any other voltages do these in batches as well. Each batch should be gradually brought up to voltage over a period of some hours and then left overnight.
You will find that your amps sound just perfect within minutes of powering up.
Comments please - no flames.
for semiconductors the failure will be in the first few hours or after many thousands of hours.
Normal measuring and testing and setting up and monitoring of output offset and bias currents usually gets you past the first few hours. No additional burn-in required.
Polarised capacitors rely on a chemical reaction in the plates/electrolyte to perform to specification.
This may be why some talk of burn-in improving the sound. basically they are comparing the final sound with in-spec or near in-spec capacitors to a system running with capacitors well out of specification.
This is very easily overcome. Don't listen to polarised capacitors that are out of spec.
Pre-condition all electrolytic capacitors by ultra slow charging them to max Vdc just like the manufacturers do before they measure them and publish the results.
This pre-conditioning reduces the leakage current without damaging any of the foil in the plates.
You can do all your 50V caps with a separate 100k feeding each one. Then do your batch of 63v caps. if you have any other voltages do these in batches as well. Each batch should be gradually brought up to voltage over a period of some hours and then left overnight.
You will find that your amps sound just perfect within minutes of powering up.
Comments please - no flames.
AndrewT said:
You won't get any flames from me
As I said in my post above, I agree. I think most of the idea of audio gear needing "break in" time got started with speakers (which do tend to need some hours to mechanically loosen up) and from electrolytic caps. But you do have to laugh at some of the amateur and professional reviews that talk about things like interconnect cables being "almost unlistenable" when new but after 48 hours of break sound "wonderful". That just shows how powerful subjective bias is in influencing what we hear.
A comment from a guy who did build his first two Class A JLH AMPs without any protection.
After completion of a project I would first wake up an amp with no speakers attached and a 40W lightbulb in series with the mains socket.
Bright light would be a sign of something wrong in the mains, or PSU part, but no real damage to components should occur.
Only a short flash indicates charging of the PSU and I take measurments of the unregulated rail voltages. Which should be near desired.
Next regulated rail voltages are checked and DC offset at the speaker terminal is checked. This is adjusted to near zero.
more to follow..
After completion of a project I would first wake up an amp with no speakers attached and a 40W lightbulb in series with the mains socket.
Bright light would be a sign of something wrong in the mains, or PSU part, but no real damage to components should occur.
Only a short flash indicates charging of the PSU and I take measurments of the unregulated rail voltages. Which should be near desired.
Next regulated rail voltages are checked and DC offset at the speaker terminal is checked. This is adjusted to near zero.
more to follow..
here is more...
Next I attach a no design , no cost 3 way system speaker to the amp and listen for hisses hums etc... Next I attach an mp3 player to the input to see if the thing actually amplifies sound (its basic purpose).
With my finger I poke around the various components and connections in the amp to check for "sloppy" soldering..
In my first amp this resulted in -22V on the speaker, I just could see it was -22v...but the no-cost system survived quite happily...
Next step is letting the amp just sit with no input for about 4 hours, and adjust DC offset to near zero (keeping an eye on my desired Bias current, because adjustments "interfere")
Last step is a cool down, and switch on to hear how large the power-on and power-off "thumb" is.
My JLH amps suffered from this, the newer more than the first. So I am in the process of adding a module which delays speaker connection on power-up, does a DC protection in operation and switches off the connection directly when mains is cut through a sensor at the secondary on the transformers.
Next I close the case and move them to the liviing room for day-to-day use.
So far for burn-in for an amp.
Jos
Next I attach a no design , no cost 3 way system speaker to the amp and listen for hisses hums etc... Next I attach an mp3 player to the input to see if the thing actually amplifies sound (its basic purpose).
With my finger I poke around the various components and connections in the amp to check for "sloppy" soldering..
In my first amp this resulted in -22V on the speaker
, I just could see it was -22v...but the no-cost system survived quite happily...Next step is letting the amp just sit with no input for about 4 hours, and adjust DC offset to near zero (keeping an eye on my desired Bias current, because adjustments "interfere")
Last step is a cool down, and switch on to hear how large the power-on and power-off "thumb" is.
My JLH amps suffered from this, the newer more than the first. So I am in the process of adding a module which delays speaker connection on power-up, does a DC protection in operation and switches off the connection directly when mains is cut through a sensor at the secondary on the transformers.
Next I close the case and move them to the liviing room for day-to-day use.
So far for burn-in for an amp.
Jos
Theoretically probability of failures go down with time exponentially. I don't know about other standards, but in Russia we used 24 hour burn-in conveyors with flexible cables and sockets going like a serpent along the wall, up then down, in OTK department responsible for QA. If some critical parameters in one of burning-in unit go out of the light on the operator's pult starts flashing, and an alarm sounds.
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