Amplifier Burn-in: How big a change is it?

[Porksoda]

Hey guys and gals,

I was just wondering about your opinion on hte subject of amplifier burn-in, particularly with IC-based amplifiers.

I built a PIMETA a few months ago, and at the time I expended quite a bit of effort trying to tune out the characteristic PIMETA harshness that a lot of people complain about. Even with my HD497s, the sound was unbearably harsh, so I decided to go with AD843s and 2-1-2 buffers, and even slightly decreased the bandwidth on the buffers. Even then it sounded somewhat harsh at the time. Recently, I was doing some careful listening and realized that the sound has now gone from harsh to actually rather soft and veiled.

I would expect this type of change with tube amps and discrete component amplifiers, but I have to admit this comes as a shock from an IC amplifier. Would you guys say this is a common phenomenon, or are my hearing/listening preferences just changing? I have enough extra BUF634s to make a whole new set of buffers. I am tempted to swap in brand new buffers in the exact same configuration they are in now, and see if there is an audible change in sound.

[BrokenEnglish]

i don't know the science behind this topic, but i'm well aware of the phenomenon, you're describing. i heard significant burn-in changes with new amps, different opamps in amps, new caps in amps etc. sometimes i even thought, that on rolling-back some formerly used opamps, they needed additional time to settle in again... well... confusing... . i'm used to give things now at least three days of breaking in before i judge on sound.

[Porksoda]

It also occurs to me that this change in sound might not be a bad thing. I mean, if it sounds kind of veiled and dull (for heavy metal) on HD497s, perhaps it will be more foreward with other headphones? I do intend to get some Grados in the near future, so perhaps some listening tests and the local dealer are in order.

[rickcr42]

burn in is very real though I don't go to the extremes some do buring in their gear using special measures-I just turn it on and use it until it "comes to me" in sonics

ever buy a reciver and when you first turn it on you think something is burning ? You can actually SMELL the new parts waking up !

not only does equipment burn in but can vary over time with heat and humidity variations AND cold to play warm up time.

Just part of the way things are and why it is a really good idea to do any perfromance measurements after a certain piece of gear has had time to warm up and stablise

[rickcr42]

BTW-I give my gear 1/2 hour of warmup before doing any serious listening and it really does make a difference that is why some people think something sounds better after a period of time and think their brain is being fooled by the listening when it is really their ears being the best audio testing instrument known to man doing their job

[blip]

The burn in difference that I saw in my PIMETA was absolutely shocking. (Biggest I've ever seen with an audio component) At first the sound through my 580s was extremely veilled (first time I ever heard the infamous Sennheiser veil... I always thought it was a myth!). While the sound was detailed, it lacked any kind of shine or sense of space... and bad bass. It was okay but dull.

After approximately 20 hours of burn in, it has changed dramatically. The veil has converted into a smoothness that still manages to shine and provide a decent sense of space. The bass has returned and, while it lacks impact, the bass that exists is amazingly well rendered. Where before its closest car equivalent would be like a Lincoln Towncar (refined, boring), now it is a BMW coup (refined, exciting but reserved). I'm hoping that with more burn in it will move a little closer to say a Porsche 911 but I'm happy with it as it is. (Though I am contemplating a simple bass boost to add a little omf the bottom end).

[Garbz]

Well burn in is definatly apparent in ICs. Usually it is exactly what you are describing, the sound going from bright and harsh to warm and musical. Many manufacturers recomend a burnin time of approx 300 hours for their gear to get to the stage where it won't change noticably anymore.

I have a tendancy to finish things at night and only get to listen for a few minutes before bed. This allows my equipment a full night + while i'm at work during the day to burnin before i even get the chance to properly de-bug it, let alone do any critical listening.

[mono]

Well I feel just the opposite, that there is no burn-in with the ICs, not the kind you'd notice after "X" number of hours rather than so slightly progressive that it might take 20 years.

Capacitor burn-in (with new caps or those sitting shelved), maybe. Socket contact degradation, certainly, as well as degradation in all mechanical contacts (but maybe improved slightly in early life due to abrasion of contact contaminants and seating issues, like after use of a POT).

Then there's perception and "getting used to it"... far too broad a topic to address.

[SpinningAround]

This is going to be controversial. I have to say, I agree with Mono. The differences are non-existent , or so close to being non-existent that even if you could measure it you surely couldn't hear it.

Whilst there are clear and, importantly measurable, differences in the sound produced by a tube amp and a solid state amp, these occur because the mechanism that amplifies the signals is very different.

By contrast, it isn't very likely that the same solid state amp 'burns in' significantly. Whilst may be measurable differences between an amp when first turned on and when measured later, these differences are both microscopic and occur over a long period of time (years rather than hours).

The problem is that when we take objective measurements out of the equation we are left with the soft grey matter between our ears. Our brains are notoriously unreliable things. Take a look at studies of the reliability of eye-witnesses for example. Ask someone who lives near a rendering plant or a paper mill about the awful smell and they will wonder what you are talking about even though you may be retching from the stench. The reality is that it is much more likely that differences you note are are pychoacoustic in nature than they are objectively measurable.

You might, on a good day, get me to agree that are differences significant enough to hear with solid state gear that runs rea.lly hot. Class A, super heated Gilmore's perhaps. And then only because there are mechanical changes as the amp heats up. Otherwise I want to see some empirical evidence.

BTW, I am sorry if this sounded like a huge troll. It isn't meant to be. I love the DIY amp scene and spend a lot of time messing around with piles of resistors, pcbs and what-have-we despite much head-scratching from my wife. You guys are awesome, partic. Tangent, PPL and my hero, Sijosae. I have an enormous file dedicated to Sijosae's stuff and I wish my Korean was even 1/100 as good as his english.

Edit: I hate being an ill spelling idiot

[Tomo]

Hi,

It really depends. What are exactly burnt-in? I think the major part of this business is due to Electrolytics Capacitors and Tubes.

Tube Burn-in you all already know. This is a half KULLING and a half stabilization of performance. Personally, I am not a tuber so I don't know. I did have a tube amp but I bought the tube already burnt-in. (The tube vender told me he burned-in for few hundred hours.)

As for electrolytics, I think its a lot to do about stabilizations; kulling is not really a necessity with advent of technology. Some of these capacitors do get damaged when soldered. They require some time to "heal." This time is referred to as burn-in process. Do I hear the difference? Personally, I do not know. It's probably because I never carefully listen till burning-in for a day or two.**

All in all, it's all contravercial. But know that you aren't all so wrong by starting to listen as soon as you take off the amp's wrapping or as soon as you solder the last soldering joint. It is hard to resist. Electronically it won't make it any difference whether you burn-in or not. So feel free to jack in. (Oh make sure you check for DC offset.)

It is so much exhirating to flick them switches and the amp thumb or hum into music. I know so well.

Tomo

P.S. Notice I don't mention about semi-conductor devices and resistors. They belong in uber-subjective region. It is safer to assume they don't really need burn-in. (Besides, you all listen so much it will burn in before you get any wiser. ... Me? I am not wiser last time I checked; Yeah I am the dood who tried to hold the soldering iron at the tip for control and I haven't change all that much.)

[Cthulhu]

Why not just test it? Get a scope, and build an amp! You should be able to compare the signal from the start of burn in till the end if your scope permits you to record the signal.

[Alick]

There are a multitude of factors which can cause electronics to change over time with use. Capacitors (particularly electrolytics) will undergo electro-chemical changes. Passing current through devices and connections generates heat which results in physical and electrical change over time. Even the electrical characteristics of simple devices like switches alter, as repeated throws cause contacts to bed into each other which can improve the contact connection, reducing contact resistance. How much each of these factors affect sound is debatable, but I have no doubt that the sound of solid state amps can change with use, which might or might not be primarily down to capacitor changes.

If you have any doubt that passing electricity through circuits causes change, consider how an electroplating bath works?

[setmenu]

I like to IMAGINE all the new components and fresh solder joints settling in
as everything gets used to all those electrons rushing about the place.
Whether any differences I may perceive are real or just the mind re-framing to
an unfamiliar sonic signature, I don't know.

Generally with diy stuff I instantly think it is the best ever sounding thing made
by the hand of man when I first switch on and listen.
After some more auditioning some sort of reality sets in,and if I find I do
not approve of the sound it very rarely improves with further listening,
just bugs Me until I make some changes.



Setmenu