How long do you usually burn in the amplifier?

There are others that believe film capacitors in particular take operating time to perform at their best.

I think you are mostly right, if you don't like the amp straight out of the box, that is not going to improve with time.  I do think though, putting a few hours on it can improve it slightly, probably best described as 'evening out'. Valves certainly smooth out over a few hours.

Absolutely 100% thought I'd ruined my original 686 when I put a PSU in and took out the SMPS

Around 3 months later (left on 24hrs a day), it came on song. Literally like someone flipped a switch and it just came alive. Was I imagining it? Dunno.

Built another 686 and it sounded ok at first....three months later....bang, came on song.

Never doubted it since.

From personal experience with many, many amplifiers across a broad price spectrum on a pretty regular basis I would more than suggest than break in occurs no question.

How long? that's the $64 thousand question?

Some simpple two stage discrete designs can be a s little as 50-75 hours, Alan eluded to capacitor dielectrics, also the constant heating and colling of the circuit board (Thermal cycling) along with many other non-moving (parts)

I could name a couple of amplifiers models than genuinely take 350-500 hours to fully blossom into the final sonic delivery.

However this also depends on how much current you are using to drive said speakers, for specific periods and with which style music / tune burst / white / pink noise tracks.

Thery don't sound bad out of the create, however listen to the same amplifier say a couple of months later compared to an exact new model, its not subtle.

At the moment I have two amplifiers undergoing break in, one is being 'exercised' via a programmable a/c dynamic load which I have coded a series of test sequences to simulate a listener from a real head banger through to jazz cats and back to Mahler. Sitting on the test rig is a big bugger of an Krell FPB 700 stereo I've just recapped.

The other amp is driving Anne's Tad R-1's @ home which are running out of phase and with a large duvet strapped over them, even though next door is 200 feet away, I like to be neighbourly.

I will share a story with you about a really nice chap who has been a customer for just over 15 years, a while ago he traded his rather nice valve amplifier in for a Liquid music amp.

We set it up in the demo room with some nice Quadral's and waited the usually 45 mins for warm upto occur, however we were left underwhelmed. "This isn't the sound these amps produce?" Pete & I are looking at each other a bit perplexed.

So I took it out placed on the analyser, surprise all good and measured well within the manufacturers specifications, still scratching our heads we placed the amp back in the system and left it playing all day all be it quite loudly!

Around 4.30pm when Pete leaves, he came in the lab and suggested I popped in the demo room smiling, so I'm walking into the listening space and thinking this isn't the sound we have this morning, now the difference wasn't earth shaking or 'night & day' lol however it was presenting a more cohesive sound with greater sound stage boundaries.

The upshot was, we ran this amplifier solidly for two weeks 9-12 hours a day at a decent 85-88dB with a varied programme at the end of that time, the easiest way to describe the change was like a butterfly unfurling its wings after emerging from cocoon. It was full of life, vibrancy, wonderful tonality and best word joyousness.

I'm sure someone is going to suggest your musical memory is playing tricks on you and you have conformation bias, your choice to do so if you wish. Both or us (and the previous owner) would disagree.

Bit of back fill to the story, chap had purchased said amplifier back in 2014 when he took early retirement, he is an avid Jazz/female vocal/strong quartet appreciator, by his reckoning he was listening to about 2-3 hours at least every other day. We did change out the valves in 2018 so he wasn't a once-a-week guy.

However, he never listened about 70dB which was an absolute maximum for him so he never ever taxed that amplifier in any shape of form.


Hence why when gave it something to think about (lol) for extended periods break in finially occurred, that is an extreme example, but it does happen and not just with amps either

Yes, we are absolute constants regardless of our physical and mental condition, time of day, level of fatigue etc etc

It is the precision electronic component that is varying wildly in its behaviour - but in some mystical way that cannot be measured or quantified and can only be detected by casually listening.

Yep, okay, that all makes complete sense.

Just on the above, it's good to have slightly (or extremely!) differing opinions as it often furthers the debate, if kept sensible, whilst refraining from the classic (and non debate furthering) 'circular argument'.

Ultimately I think what matters more is not necessarily a yes or no definitive, but the message that there is clearly room for differing opinions as well as keeping an open mind.

Regarding the opinions offered so far (and back through years of similar threads), those with in depth technical knowledge and experience also differ on this subject, so nailing your colours to one particular mast is a bit too absolute for me, but maybe that's just me.

All opinions welcome as ever.

I have no definite idea about which parts need burning in but it does exist and has caught me out a few times . many years ago I picked up a crossover for my then passive KEF 103 Reference speakers these were all the same value as the original but with film capacitors and better specified resistors all metal film 1% . This was made by another ethusiast who sadly died before using them so never had a signal through them . Did the deed and removed my originals and put these in place checked the wiring and made sure my soldering was secure . Put the speakers back in turn on and yes they were the same speakers but they sounded tight and a little constricted at both ends . So left them all night with some lower volume music playing varied mix and came back to them next day . Sound was now really nice and not only were they back to what they had been but they were better and much improved . Had I not had a little patience and just said that does not work and does not sound better and just removed the new crossover I would never have known .

I also use NVA amps and they say quite clearly that when the transformers and capacitors are new they need a burn in time . They seem to be right as from new the sound gets better over a two or three day period and then really blossoms in to what you expect from that amp .

Placebo effects are very real it doesn't mean there's anything changing in objective reality.

I experience them just the same as everyone else. The only difference is I accept the fact that my perception is not entirely reliable.

Example - I bought some rubber washing machine feet from Lidle to raise a sub off the floor. I hadn't set it up and the feet were sat on a  shelf. 

I was reading a thread about isolation and on a whim decided to put the feet under my amplifier, whilst it was in use. 

The sound immediately changed for the worse. It was so bad I took the feet out after about a minute or two and normal service was resumed. 

There is no possible way that those feet changed the signal being output from the amplifier in any way. Yet I perceived a big change in the sound. Entirely in my head. 

especially odd since received wisdom is that isolation/damping improves the sound. So you would think I would either perceive an improvement or no change. But these thing are not predictable.

This is why there is such a big market for foo and why people are evangelistic about it. 'I heard it!' No, you perceived it. Not the same thing.

Back when i started building the BB3's...quite some time ago now, when i was still finding my feet, i built a BB3 for myself. I took it to Alans for measuring, and when he checked it out, the RIAA was out in the HF. Not loads, but enough to cause an overshoot on the squarewave. Alan corrected it, and i took it home in perfect measuring condition....seen with my own eyes.

After a week, i felt i needed to take it back to be checked as it had lost some HF extension, again, just a little, but the shimmeringly nice HF was a little flat.

He measured it. It had now a slightly rolled off HF edge on the square wave.

He corrected it....with the original value resistors i had previously fitted.

We thought it to be a little odd. Only 10 hours or so of use had passed between measurements, but there it was. It had changed audibly, and measurably. We repeated this test later on when i sold a couple, and the exact same thing happened. Overshoot when just built, 10 hours later, perfect.

The valves were tested and a known quantity, so i am 100% confident it wasnt the valves. The measurement device was the same, the probes etc, nothing changed and were calibrated too. So something else must have taken some time to bed in. This is a test i can now perform at home, and have, and the result is the same. every brand new BB3 has a small HF overshoot of the Squarewave. After 10-15 hours, it flattens off. Unfortunately, until someone orders one, i cannot repeat and demonstrate it...but when they do, i will.

You can tell yourself that lidl feet CANNOT make a difference, or that burn in is a lie/nonsense/impossible, but you can't tell me. I have seen a device change and the only difference to it was how long it had been in use. It never changed again after that initial period BTW.

But where are your controls? You say nothing else changed but you are just assuming that and inferring that something unknown happened. Clearly something happened but there's no grounds to state that it was something that could not be quantified with sufficient testing, an 'unknown unknown' if you like.

In any case I am not disputing that a brand new capacitor will take time to form and it could really be that simple. That's not the same as an amplifier taking hundreds of hours to 'come fully on song', a claim that has zero evidence behind it.

So again, brand new unused capacitors again - sorry but the idea that it will take a month (720 hours?) for the 'final opening out' to occur is just absurd.

Paul is in a good position to test this though, he can take an amp with, say, an hour on it (which should be more than sufficient for the caps to form) and an identical one with 720 and do a blind comparison. Or maybe even some measurements. 

If he or anyone else can relaibly differentiate between one hour and 720, or if he can show measurement changes that indicate an potentially audible difference then I will pay attention.

But no manufacturer does this even though many will claim that their amp needs 100 hours or some other arbitrary amount of burn in. It does? Then show us the evidence.

There are a number of reasons they say this, probably the main one is punters expect to be told this as it's often stated by magazine reviewers attempting to sound professional ('I let the amp burn in for 200 hours before starting serious evaluation') so there's an expectation to be met. It's also helpful to discourage returns within the 14 day statutory period, and there's no down side to making the claim.

As with any unsubstantiated claim there are downsides to it being paraded as fact without any evidence. We have a member here dissatisfied with his new speakers and even after a few weeks still hoping that they would burn in and improve - because this is what people were telling him. 'Hundreds of hours of break-in'.

How long would he have continued being dissatisfied with them, kidding himself that they were improving a little bit day by day? If a technically knowledgeable member had not pointed out to him that his amplifiers can't properly drive the load, possibly he would have eventually decided, after months of dissatisfaction, that they were not for him and have to sell them on at a financial loss. 

So there are real-world implications and consequences  for making unfounded technical claims.

How long I used the Phonostage before something audibly changed.