Capacitor burn-in? Is it real or psychological?

[debk]

I have replaced capacitors in some of my equipment, most recently I put Russian FT-3 Teflon caps in my Seduction.  Initially I felt that they sounded  shrill and thought it was a mistake to use them.  I did not initially burn them in, since I wanted to see if I can perceive a difference as time went on.  I have about 10 hours on them now and they are starting to sound more mellow, I expect they will get better with continued time.  So if I trust my ears then I must admit that capacitor burn-in is real

So what is going on?  Is there some electromechanical or quantum process  process on in the capacitors. Could the changes going on actually be in my head, some kind of audio neuro adaptation for lack of a better term.  I have to trust my ears, but i don't like not having a real explanation.

I don't know if this has ever been done, but it may be an interesting experiment.  Under controlled conditions do a RTA audio analysis or, other more appropriate test, first with the fresh caps and then with the same caps broken-in.

Debra

[Paul Birkeland]

Some time ago I was pretty unsure about capacitor break in myself.  It was only after trying teflon V-caps in a phono preamp several years ago that I was overwhelmed by the effects of capacitor break-in.  I am quite sure now that with a frequency generator and a scope that one could measure the effects of a teflon V-cap breaking in, especially in the low frequency region.  This would in turn seem to imply that something changes with the dielectric constant or the distance between the plates, or that the equation for capacitance is somehow incomplete. 

I have heard that Teflon is pretty soft, and that it can change in thickness over time, which might help to explain this effect.  In metalized poly caps, like Auricaps, this gets harder to explain (or at least dream up an explanation for this).

[JC]

I'm afraid I don't have any sort of definitive explanation for you, but I've certainly heard caps change with hours of operating time.  More than once I've had new caps sound OK to begin with, then get really awful for awhile before they run in and sound good again.

My pet theory has been that the dielectric must undergo some subtle changes at the molecular level, but that is no more than a fancy of mine.  I'm not sure if a test has been developed yet that can measure any quantitative values that are changing over time.  But, my experience with caps sounding OK-then-worse-then-better has convinced me that there is indeed something going on beyond the psychological.

BTW, I have been looking at the pix you have been putting up of your kits, and I must say that I think they are gorgeous!  I love the use of color, an ability I often lack!

[Paul Joppa]

I too was skeptical in the extreme at first. The "get used to it" effect has been well known for decades - how can you tell whether that's what's happening or not? What convinced me was blind testing, in the form of running an amp with new capacitors into a dummy load, so that I had no chance to get used to the different sound - just listening for 5 minutes at the start, and again after some 50 hours (for polypropylene caps; Teflon caps in general seem to need 200-500 hours before they really hit their stride.) Same experience with transformers.

I have a career as an engineer behind me, but still no convincing explanation. In fact, darn few explanations that are even plausible! Here are two barely-plausible ones:

1) mechanical "settling down", i.e. micro mechanical motions that eventually stop as the plastic deforms into a more stable position. The electrostatic forces are certainly real; you can hear sound coming from most capacitors if they have signal on them and the room is quiet.

2) Dielectric absorption is nonlinear and hysteretic, similar to magnetic hysteresis. Just as iron transformer cores are demagnetized, it may be that biases in DA can be removed to settle around a normal operating point.

I'm sure there are many more equally improbable theories out there.

[debk]

I guess the bottom line is sit back and enjoy the great sound.  But as a physician and one time engineer I hate it when I can't find a scientific explanation for something.

Debra

[Paul Joppa]

...But as a physician and one time engineer I hate it when I can't find a scientific explanation for something.

:^) Yeah, me too! If you can find a copy of the book "What Engineers Know, and How They Know It" you might find it interesting.

[bobster]

Is this the book to which you were referring?

http://www.amazon.com/What-Engineers-Know-How-They/dp/0801845882#noop

[corndog71]

I just bypassed my Sex amp output caps (Erse) with a couple of .47uf V-Caps.  The V-caps aren't even close to burned in but the difference was instantly noticeable.  I noticed increased width and depth with the soundstage.

I've also found this to be true for caps in speakers.  Bypassing with teflons (I prefer Sonicap Platinums) is a terrific upgrade.  For speakers they work best in tweeter circuits.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi576.photobucket.com%2Falbums%2Fss207%2Fcorndog642%2FBottlehead%2520Sex%2520Amp%2F173ae391.jpg&hash=d57721c7846d90064cffecb3dc6bc95df4eeac43)

I would just like to add that this little mod has completely changed my mind towards headphone listening.  I've been using a cheap pair of Phillips ear buds with my ipod for months and rarely used the sex amp for headphone listening.  With the bypass caps installed the sex amp is driving them like never before.  Bass detail is is so much fuller and distinct from the rest of the recording.  Now I really want to invest in some better cans.

I hadn't really put much thought into doing this.  I was originally using the v-caps as output caps for a Dynaco Mk 4 clone.  But I didn't feel like dropping another $250+ for another pair so I just thought I'd throw them into the sex amp for fun.  Mind you, my sex amp is mostly stock except for the signal caps and some added silver wiring to the outputs.  The V-caps really crank up the resolution several notches!

[Paul Joppa]

Is this the book to which you were referring?

http://www.amazon.com/What-Engineers-Know-How-They/dp/0801845882#noop

Yes - that's the one. I was most impressed with the propeller section, but he makes many other good points too.

[debk]

Thanks, I just order the book from Amazon

Debra

[dmannnnn]

I've experienced 'burn-in' with electronics that are 30 years old.  Obviously it was most likely a psychological effect.  The brain is an amazing organ and can do things we can't yet comprehend.  Humans are endlessly adaptable creatures and our preception is a fragile concept.  The way we perceive the sound of our hi-fi can be affected by nothing more than our mood at the time.

As far as capacitors go, I've have perceived burn-in.  I have no idea if it was true or merely an illusion.

 On the other hand, I believe an analog signal has properties that we have not yet discovered, parameters beyond voltage, frequency and the like.  These might be caused by interactions at a sub atomic level and even involve additional dimensions, seriously.  I'm not a scientist, but I do know there are many things we don't know or even suspect in the natural world.

[Grainger49]

I think you know my vote.  

In 1984 I started up a line of VFAC (variable frequency AC) drives.  The GE Engineer and I spent two hours forming the capacitors.  GE says that there is something to it too.

[ssssly]

I conducted a rather informal experiment to test this some years ago. I replaced all the caps in my Paramours. I left one sit and burnt the other one in for 100 hours into a dummy load with a 20 to 20 signal sweep on the other. Then I listened to them.

They sounded nothing alike. The un-burned in amp was shrill, sibilant, and lacked bass impact.

I then burnt it in for 100 hours, like it's sibling, and listened again. They both sounded the same. Much warmer, stable sound stage, and authoritative bass.

If I remember I may try this again and scope my Gigantamour project now that I have a computer based o-scope.

I also just recently came across a thread in a forum someplace, don't believe it was here, of someone who did something very similar over a much longer period of time and scoped the amps. The scopes too showed difference in waveform shape and continuity. And if I recall didn't stop changing for almost 600 hours.

I however have no idea why this would be true even though my experimentation, subjective experience, and the experience and experimentation of others seems to confirm this. So I chalk it up to one of those mysteries, like how many licks it takes to get to the center of a tootsie pop, and press on.

[richardl]

David Manley refers in his book to forming his caps at higher temperatures to ensure their stability and durability during use.  He slowly brings them up to B+ in an oven!  He thought that cap breakin was very important.  IMO it is very observable in the first few days with a new homebrew amp with caps that are new of any type.  I have an amp with no electrolytics whatsoever and for the first few hours I was wishing that I had not bothered replacing the electrolytics, as it was awful.  Several days later the nolytic amp was sounding very good.