Electrolytic Caps [Good or Bad?]

[R.G.]

Anything approaching a true A->B test is dangerous to many businesses; "break in periods" avoid a temporally close comparison and allow weak human psychology to take over.

I think that's exactly correct - so correct that the hifi tweakos will do anything to discredit A-B-X blind testing, including pointing out that the results usually fail to find any differences between whatever is being tested. Rather than take that as an important result, they try to discredit the test. Classic political manuvering, even if unconscious. Remember, "no difference observed" is as valid a result as "A>B" or "B>A".

I personally view the refusal to accept results of double blind testing as a comment about the person doing the refusal - but that is just my opinion.

I've observed the phenomenon of capacitor burn-in many times. In fact, now, before I install plastic film capacitors, usually polypropylene, I burn them in by hooking them across the house AC for a couple of days. I spoke to a capacitor manufacturer about it once, and they gave this method their approval. I used to experience that "brightness" of film capacitors when first installed, but this gets me past 90% of it. If, for some reason, I don't have time to do it, I can usually tell the difference.

OK, how much money would you bet on being able to identify broken-in versus non-broken-in capacitors which are otherwise identical, over a range of capacitors, multiple tests, in a double-blind test designed to isolate you from any pre-information, at a rate that's statistically better than random guessing?

Then remember that sales droids are betting tens of thousands of dollars on your NOT being willing to do that. Or able to do it if you were willing.

...whenever possible, I like to try to understand the science behind it.

Me too. But I had to earn a living understanding the science behind it.

I discussed capacitor burn-in once with a graduate student in textile engineering who works with things like polyester and polypropylene on the level of their molecular chemistry. He said that something might very well be happening at the boundary of the plastic film and conductive foil layer as a result of the application of AC voltage, which does cause tiny amounts of motion inside the capacitor. For example, it could involve the dielectric conforming itself more closely to any microscopic irregularities on the surface of the foil. He also speculated that this could involve tensions placed on the film during winding.

I've discussed this and similar issues with graduates in materials sciences for electronics over some decades. I guess it depends on who you want to believe.

The "show it to me on an oscilloscope" argument is also b-s because I can often hear things better than my eyes can discern them on an oscilloscope screen.

Who said anything about appearance on an oscilloscope? I said "measurement". Oscilloscopes are an indicator, but no, you can't for instance distinguish 0.1% distortion from 0.001%; well constructed A-B blind testing will do this. So will a well designed distortion analyzer. The bottom line here is that the well-documented tendency of a human to self-delude requires that the human have every bit of expected results and foreknowledge of the test removed to be *capable* of rendering an impartial verdict. That's *why* double blind tests were devised: not only do the testing subjects who give an opinion on the subject being tested have to be kept blinded about the test, the humans administering the tests have to be kept blinded about each test case to avoid them *unconsiously* telegraphing information to the test subject. Go google "Clever Hans" the horse.

If you ask a professional in medical or psychological testing, they will tell you about testing where humans have to render an opinion about what they perceive. And double blind testing. Note that Clever Hans' exposer himself could not *stop* delivering cues to Hans even when he knew what was happening.

I'd dare someone to try to distinguish a medium-quality digital piano from a real piano based on a signal on an oscilloscope screen, even though it might dead bloody obvious to anyone who plays a real piano.

Yep, the o'scope is a low- to mid-fidelity tool for testing audio quality. That's why it's not used for that.

I remember seeing some blind tests done where people were asked to tell the difference between digital recording and analog, and they couldn't. Some people hear better than others, that's for sure.

Tee hee! See above. Clever Hans and other early episodes in psychological testing were incredibly important in understanding human perception testing. Humans simply cannot, on a reliable basis, produce accurate perceptual data if they have any cue whatsoever what is being tested or how. They cannot get around their internal expectations and biases even if they are consciously trying to invalidate those biases. And yet, they persist in saying that not being able to tell the difference on an audio taste test invalidates... the test (!?).

When friends visit my place and listen to CD's on my stereo system, they always complement me on how "real" it sounds. But, if they went to shop for similar sounding system, more than likely they wouldn't hear the "Quality" of the sound, from one system to the next. And then they would end up buying what the salesman said was the "Best" sounding system.

I completely agree. It's totally consistent that this would happen.

There's a lot going on with sound, and when audio designs are put together mostly by ear and trail and error, the results usually come out great.

Hmmmm... so a not-formally trained person puts together audio systems by trial and error, not trying to avoid their internal biases, and they usually come out great? I'm going to guess that if a person is invested in "those experts" being wrong all the time, that they probably do add extra weight to an untrained person's coming out ahead.

What a surprise.

I realize that I'm just talking here. My experience over decades is that no one who has bought into audiophile subjectivism is capable of recovering. It just doesn't happen.

[Old Tele man]

...FIX what's broken...let SLEEPING dogs lie.

...simple: potentiometers "wear" out, electroytic capacitors "dry" out(*)







(*) --"other" failure mechanisms exist, but that's your job to learn about them.

[guitician]

Worse yet, the brain tends to make up the picture which has been suggested to it. These things are survival characteristics for humans in the real world, where a twig snapping or grass rustling may enable one of your ancestors to form a picture of a saber-toothed tiger about to spring. That same mechanism, when used for savoring audio, leads to a vulnerability to the lying, cheating, greed of other humans.

So, for someone to react to the "Perceived" change in a caps sound, there would have to be a real "rustle" or "snap", or then those changes would have gone unnoticed. I find it hard to believe that all these listeners are delusional.

Hmmmm... so a not-formally trained person puts together audio systems by trial and error, not trying to avoid their internal biases, and they usually come out great? I'm going to guess that if a person is invested in "those experts" being wrong all the time, that they probably do add extra weight to an untrained person's coming out ahead.

Hmmm... so the experts never listen to and adjust their designs afterwards?

[Prairie Dawg]

What a surprise.

I realize that I'm just talking here. My experience over decades is that no one who has bought into audiophile subjectivism is capable of recovering. It just doesn't happen.

Such a cynic. I am quite sure that the International Brotherhood of Carthusian Bauxite Miners (a little known offshoot of the Knights Templar) which only mines the finest aluminum for capacitors during certain phases of the moon would disagree with everything you say.

What was it Tug McGraw used to say, "You gotta believe!"?

[Rhodesplyr]

I realize that I'm just talking here. My experience over decades is that no one who has bought into audiophile subjectivism is capable of recovering. It just doesn't happen.[/QUOTE]

Of course, that's just your subjective experience ;-)

I once replaced the original silicon diodes in an early 1960s Dynaco SCA-35 with current production soft-recovery diodes, on the theory that the current ones are lower-noise. The improvement in sound was so pronounced, it surprised me. So, I tried the same thing on the bridge of one of my Leslie 122s--no difference whatsoever. I was predicting some change, but I perceived none. Bandwidth limitation in the Leslie or just no difference? I don't have an explanation.

Speaking of bandwidth limitations, I've had my hearing checked a few times, most recently when being fitted for a new pair of on-stage hearing protectors. I can still "objectively" hear to ~23kHz. I do hear things other people don't. Perhaps, psychologically, the denial of the subjective perceptions of some by others is displaced resentment at their inability to perceive things that others do. If you're going to invoke psychological mechanisms, let's open the door to all of them ;-)

I would take the bet that I could repeatably distinguish pre-burned-in vs. non-burned-in examples of the same brand of, say, Panasonic ECQP 0.1uF coupling capacitors in the same amp, under conditions where all other factors were controlled under A-B-X testing.

I've talked to materials experts who say burn-in is reasonable, and you've talked to those who say it isn't. Thus, there seems to be some disagreement about it even among objective scientists.

On the other hand, I do NOT own $1,000 power cords or write extensively about the sonic superiorities of silver wire over copper. Someone asked me recently what I thought about cryogenically treated tubes. I responded that I guessed they were "cool," but that was about it. I had someone tell me recently that it was vitally important to install a $30 Jensen copper foil in oil capacitor and cloth-insulated wire inside a Stratocaster for the best tone. I remain skeptical.

In general, I try to maintain some balance between science and subjectivity. One of the things I've written about in my academic career is the appearance of the medical expert in the 19th century. If you want to read some crazy "science," pick up a 19th C. medical textbook and see what was regarded as objective fact by "experts." Or read Charlotte Perkins Gilman's famous short story "The Yellow Wall-paper."

[Steve Conner]

Look! Rare vintage TOC electrolytics! Low starting bid.

These units have an amazing tone* and will transform** your Fender Twin or similar. Satisfaction*** guaranteed.




*The last sounds they made were Phizzz, Splurt, Sizzle, BANG!
** Transform it into a smouldering wreck.
*** Mine, not yours, sucker!

PS Thanks for the huge post, RG. For what it's worth, I was an audiophile, but I got better. My turning point was a summer job in the radio studios at BBC Scotland. One day my boss asked me to make up some speaker cables for one of the studios. I was like, "Where's the speaker cable", and he replied, "There's no such thing. Use that reel of line cord over there."

I'm thinking of founding the 3dB Club, we refuse to buy anything that makes less than 3dB of a difference to something.

[R.G.]

So, for someone to react to the "Perceived" change in a caps sound, there would have to be a real "rustle" or "snap", or then those changes would have gone unnoticed. I find it hard to believe that all these listeners are delusional.

Give the posting a careful read again. Nothing was said about the need for a rustle or snap - only that the ability to form a fully formed image about what might happen from very fragmentary data was a survival advantage. Don't try to read more into it than I said. The people that formed the "delusional" images of being tiger chow were the ones that, on average, reproduced more, as they were not there when the jaws closed.

If you want to say that forming a full image from partial data is delusional, you can; I didn't say that. What I said was that forming a picture from fragmentary data was something that humans do very, very well, and so readily that we're in general unaware that we do it. I can find URLs for you to read up on that if you like.

And I did not say that "all these listeners are delusional". I said, meant, and stand by that they form images which may or may not be accurate based on whatever data their senses give them, plus a whole lot of post processing inside the human brain. Again, I can find you references if you have issues with that.

Hmmm... so the experts never listen to and adjust their designs afterwards?

You really need to read the words I wrote. I didn't say experts didn't listen to and adjust designs.

But I did respond to your comment that good audio systems (presumably most or all by the context) are put together by trial and error. I don't know many experts who put together anything by trial and error. They put them together by design, by intent, by the knowledge learned by training and experience, as opposed to trial and error. The million-monkeys approach to Shakespeare probably is not used by experts. There is a difference, and not the one you are implying.

Of course, that's just your subjective experience ;-)

Of course it is. That's why I said what I did. Wasn't that obvious enough not to need restating?

I once replaced the original silicon diodes in an early 1960s Dynaco SCA-35 with current production soft-recovery diodes, on the theory that the current ones are lower-noise. The improvement in sound was so pronounced, it surprised me. So, I tried the same thing on the bridge of one of my Leslie 122s--no difference whatsoever. I was predicting some change, but I perceived none. Bandwidth limitation in the Leslie or just no difference? I don't have an explanation.

Whereas we now can measure snap-off ringing or lack thereof, in rectifier diodes, and we now know that the specific conditions of diode, wire placement (and therefore inductive and capacitive parasitics) can greatly affect the need for snubbing diode turn off. I don't know that's the explanation, as I'd have to do the examinations on the equipment involved to know, but it could well be that the diodes didn't do snap-off ringing on the Leslies, or that other factors prevented diode turnoff transients from being propagated into the audio path. Mother Nature is very picky about the smallest of Her Laws being followed at all times.

Speaking of bandwidth limitations, I've had my hearing checked a few times, most recently when being fitted for a new pair of on-stage hearing protectors. I can still "objectively" hear to ~23kHz. I do hear things other people don't. Perhaps, psychologically, the denial of the subjective perceptions of some by others is displaced resentment at their inability to perceive things that others do. If you're going to invoke psychological mechanisms, let's open the door to all of them ;-)

Congratulations. I'm all the way open to invoking psychological mechanisms, or other mechanisms of any type whatsoever where the mechanism can be (a) repeated by disinterested observers and (b) at least conceptually measured.

In response to the very soft drive-by comment, displaced resentment is a fine thing to allude to, oh so softly. Sorry, but that's not my issue. You're not the only one whose hearing has been tested. And if we want to allow "displaced resentment" as a mechanism, there are all kinds of things that can cause displaced resentment, and the whole implied chain of responses that theoretically might cause. Shoot, I could conceive of a possible situation where someone concludes the "experts" must always be wrong because one hears things that others do not.

Of course, historically, hearing and seeing things others do not has been a chancy thing to have happen to one.

I would take the bet that I could repeatably distinguish pre-burned-in vs. non-burned-in examples of the same brand of, say, Panasonic ECQP 0.1uF coupling capacitors in the same amp, under conditions where all other factors were controlled under A-B-X testing.

I'd dearly love to take your money.

I've talked to materials experts who say burn-in is reasonable, and you've talked to those who say it isn't. Thus, there seems to be some disagreement about it even among objective scientists.

Yeah. That's why I insist on measurements. Instruments may or may not be sensitive enough to dredge a signal out of noise - as humans do with patterns really there, or sometimes not, as perceived patterns in video-noise snow. Experts' opinions are just that, opinions. They can be deceived or self deceived. 'Course, if you wanted to plant corn and get a big crop, you might be more interested in talking to a practicing corn farmer than a tobacco farmer. Just a thought.

I had someone tell me recently that it was vitally important to install a $30 Jensen copper foil in oil capacitor and cloth-insulated wire inside a Stratocaster for the best tone. I remain skeptical.

I would remain skeptical too. I laughed until tears came to my eyes when I read about the claims of water-jacketed speaker cables. The problem is that there are people who really do believe that stuff, wholesale. And they tell their friends. And they post it on the internet, so it must be true.

In general, I try to maintain some balance between science and subjectivity. One of the things I've written about in my academic career is the appearance of the medical expert in the 19th century. If you want to read some crazy "science," pick up a 19th C. medical textbook and see what was regarded as objective fact by "experts." Or read Charlotte Perkins Gilman's famous short story "The Yellow Wall-paper."

The expert-of-the-day syndrome is always a danger. Georg Ohm received a lot of guff I understand when he was unraveling how voltage, resistance and current related. The prevailing expert opinion was that voltage was equal to resistance times current raised to some power. Ohm was soundly beaten upon for saying the exponent was unity.

The problem was the crude instrumentation at the time. Measurement was crude, and it was not always possible to distinguish things that closely. Of course, the argument quietly faded away when the instruments got accurate enough to do the measurements to an acceptable degree of accuracy.

Medicine in particular has been the repository of bad science, not least because of the willingness of people to believe what they're told, the placebo effect, and the sheer volume of money available to people willing to lie convincingly to sell something. By contrast, the audio huxters are small potatoes indeed.

When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind. It may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science.

Of course

If we knew what it was we were doing, it would not be called research, would it?

[tedmich]

Bravo RG! You are a scientist AND an auditory aesthete, proving these needn't be mutually exclusive.

I think you will find the discussion I linked to previously quite amusing, as one poor empiricist actually tried to quantify capacitor tone and "break in". The poster (spkrdtr) actually passed on the report (here: http://www.polkaudio.com/forums/atta...4&d=1207187391) and got crucified! (You dare to even ask the question blasphemer!)

To quote one dismissive expert (+11k posts vs spkrdtr's 8):
"Another friggen scientist
Please take your head out of your ass. I swear you can hear so much better that way. I don't need charts to tell me what sounds better."

goring sacred cows...what fun!

[guitician]

R.G. the "rustle and snap" quote was taken out of context. I was trying to state that a change in a caps sound is "change" and not "made up". Looking at an optical illusion requires that you "Look" at it, sometimes it will appear to change by itself. This will not happen for everyone the "Looks" at it though. I know that perceived effects in sound are real, and do play a part in the audiophiles experience. If a graphic artist used this mechanism in his art, does it make it not worth as much, because they have left part of the work to our own brain? If it doesn't work for your particular needs, don't buy it.

Sound making devices(musical inst.) were first put together by creative people, not by trained engineers. The first devices for audio production were brought about by inventing minds exploring uncharted areas of the physical world, who mostly used their ears. That's all I was getting at by "trail and error".

I think it's best that the music do the talking...I'll just listen.

[rudutch]

So,

after reading all these posts, I still am not enlightened.

The conclusion:

Some say 'change 'em'
others say
'if it ain't broke (leaking / swelled) don't fix it'.

Is this the whole rosewood Vs maple fender neck debate in a different genre?

I was hoping for a more definitive post as I have 3 amps form '65 to '73 all with original caps (none leaking / swelling / etc.) They all get used 3-5 times a month for an hour or more

You guys do amaze me with your knowledge though

[guitician]

Well that depends if you:

Have the time and money to replace all the e-caps just to have a secure sense that your e-caps are newly replaced and may be more reliable because of it.

or

You play your amps with a backup and can just roll with a failure, should one ever occur.

[R.G.]

Well that depends if you:
Have the time and money to replace all the e-caps just to have a secure sense that your e-caps are newly replaced and may be more reliable because of it.

or

You play your amps with a backup and can just roll with a failure, should one ever occur.

I completely agree with that. Old caps may work for a long time. They may also die the next time you turn them on. There's no way to know about one specific cap, so all you can do is play the statistics.

The amps from '65 to '73 have caps that are 36 years to 44 years old. They are clearly at the end of the bottom of the "bathtub curve" for failures, and may in fact be remarkable as survivors. But nothing lasts forever. One day they will fail. The question is - what are you going to do about it?

If I have an application that demands my amp not fail on me during a performance situation where I may not have a backup, I will insist on having the predictably failing parts be within the low-failures part of the reliability bathtub curve.

If I could stand for a cap to fail, and then take it off line and use other things while it was being repaired, I might not insist on the caps being less than ten years old.

What this whole argu... er, discussion, has missed is that aging electro caps also change an amp's tone. This may be in a good way, may be in a bad way. And an aging cap may cause funny problems with amps, like intermittents, oscillation, and ghost noting.

But if you can stand for your amps to fail and wait for them to be repaired, you don't have to preemptively replace them all. You can wait for them to fail, then replace them. I personally dislike the prospect of likely failure, so I'm nearly always on the side of "let's make this reliable". But not everyone needs or wants that.

Bottom line: it's up to you. They *will* fail someday. You just don't know when. If you're OK with not knowing, and letting them fail first, then fixing the amp, so be it. If you need them to NOT fail, or if you're having funny problems with the amp, or you just wonder what the amp sounded like when it was new, you may want to replace them. It's kinda like getting a flu shot. If you can deal with the consequences, you don't necessarily need the prophylaxis.

I deal a lot with people who can't stand for their amp to fail just before a performance in West Bug's Ear, so I advise replacement.

It's worth noting that playing an amp a few times a month for an hour or so is one of the things which should prolong capacitor life. They don't get too hot for too long, and get regular doses of re-forming voltage. Like people eating healthy foods and getting a healthy amount of exercise, it's a good regimen. But then there's Jim Fixx, the late-60's running guru who became famous for promoting running when running for exercise was new. He was healthy and vigorous - until he dropped dead of a massive heart attack at age 52 after his daily run.

It's always something. Figure out what works for you and do it. You know the arguments now.

[soundmasterg]

Hey R.G., if I have some LCR caps and some Sprague Atom caps that are new but have been sitting on the shelf for 8-10 years, should I bother to try to reform them and use them?

Greg

[R.G.]

Hey R.G., if I have some LCR caps and some Sprague Atom caps that are new but have been sitting on the shelf for 8-10 years, should I bother to try to reform them and use them?

Greg

I would, if only to make sure that they don't leak and overheat when they're fired up.

Re-forming is a breeze: hook them up to their rated DC voltage, but through a 100K resistor. When the voltage across the 100K drops under 10% of the rated voltage, you can hook up the voltage directly. This may take some hours if the caps have a reparable problem. It may never happen if they are too far gone. Probably good brand name caps will recover fine.

[novosibir]

I don't want to piss onto anyones opinion or experience, just want to tell, what has happened to me once...

... it's been already a few years ago, as one of my customers came with his early 70' Marshall SLP (the one with the six can caps on top of the chassis) and had a prob with a high pitch squealing from time to time. It turned out, that one of the two "+" contacts of the preamp filter cap was loose - the lug/rivet connection was loose and some oxidation already went in between. By wiggling on the contact you could provoke the squeal, or stop it.

If I recall correctly, Erie caps were in this amp, but already about 35 years old, so I've recommended, to swap all six cans with new ones. And because I wanted to do the customer a favor, I've ordered a 'six-pack' of the in HiFi circles highly regarded "Mundorf" can caps. The Mundorf 50+50/500 have the same diameter, just are a bit shorter like the TAD's. I've measured the Mundorf's before swapping in and recognized, that ESR was overwhelming great. Though they were new, I've formed the caps in the amp before first firing up - a 100K in the B+ between the rectifier diodes and the 1-st caps, yellow H.T. CT still disconnected, still no bleeders (the 56K's) soldered back to the screen filters and of course w/o tubes - and surprisingly after less than one hour the voltage drop across the 100K was less than 2VDC, what proofed a negligible low leakage current.

I thought "WOW" by myself and thought, how happy the customer probably will be, because I couldn't notice any ghosting even with the amp set to very high volume!

Two days later the customer called me, said that at rehearsing yesterday he couldn't recognize his amp anymore...

... but no! He wasn't happy! He's been whining like a kid, asked what else I've done to his amp - asked, why it does sound so much different now! He said, that the amp now sounds so polite, so clean and literally like polished - quite like a new amp from the 90' and not like the old British Beast from the early 70' with the nice british dirt in the sound as before!

And after some discussion, where I've affirmed, that I haven't done anything else than only swapped the filter caps including the bias caps, adjusted the bias and still cleaned some ground connections, he begged, to put back his old filter caps again, except the failed one of course, as soon as possible - and still showed up at the same evening, to bring his amp back.

I haven't swapped back his old Erie's in the amp, but six NOS LCR's from 1993, from which I still do have a huge stash. They measured much worse concerning ESR compared to the Mundorf's, they also took about 12 hours forming time after the 100K method and voltage drop across the 100K after 12h forming time has been about 5 volts as opposed to the Mundorf's value of less than 2 volts.

By playing the amp I could recognize some slightly ghosting at higher volume settings, especially the open G string and playing beyond the 7-th fret, but it's been tolerable.

In the evening the customer picked up his amp - and called me up the next day very late, just before midnight..... and he's been sooo happy again He's been so much surprised, that his amp came to life again and got back its 'old sound' like before, just even a bit better and said, that he nearly couldn't stop playing his amp again in the reherasing room, hence his phone call came so late.

Yes, it seems that sometimes the physically regarded worse components nonetheless are the better components for guitar tube amps

Have a nice Sunday!

Larry