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Thread: The truth about caps

  1. #71
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    Quote Originally Posted by guitician View Post
    Polypropylene and Foil are great, but are pricey.... anyone try CDE 940C30S1K-F .01 3000V $1.5 and can slew 2568 volts a microsecond!
    Wow! Whatta slew!

    Of course, a 1000W amp output at full tilt with a 20kHz sine coming out slews a maximum of about 22V/uS, so a 2568V/uS slew may be a bit of overkill.

    Reminds me of the sign: "Danger! 2 Million Ohms!"
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    Regarding the OP: The best way to find out is to try it yourself....

    Place a high quality polypropylene in parallel across an interstage coupling capacitor and see if you can hear a difference (maybe even solder just one end so you can "switch" it in and out, provided the voltages are safe enough). My experience has been that there is often a perceptible increase in clarity, particularly if the capacitor being bypassed is a large electrolytic. Everything in the circuit makes a difference, down to the solder and traces themselves. The question is whether or not the differences are significant.... and that can be a subjective matter.

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    Quote Originally Posted by R.G. View Post
    so a 2568V/uS slew may be a bit of overkill.
    I thought overkill was the driving force behind all of this, no?
    ST in Phoenix

  4. #74
    Noodle of Reality Steve Conner's Avatar
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    2568v/us across a 0.01uF cap implies a current of about 25 amps.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

  5. #75
    Senior Member guitician's Avatar
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    CDE's UNL ElectroFilm series has a max. peak current of 2200 A. I bought a couple 30uf/600v back when they were $15 ea. I though it was worth the extra $$ to have a little overkill

    Wouldn't you want your audio engineer to have "Golden Ears", instead of just a lot of electronics theory?
    Last edited by guitician; 12-17-2009 at 03:27 PM.

  6. #76
    Senior Member guitician's Avatar
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    Quote Originally Posted by Phostenix View Post
    I thought overkill was the driving force behind all of this, no?


    Na....just a lot of fun

  7. #77
    Senior Member hasserl's Avatar
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    Quote Originally Posted by 12Bass View Post
    Regarding the OP: The best way to find out is to try it yourself....

    Place a high quality polypropylene in parallel across an interstage coupling capacitor and see if you can hear a difference (maybe even solder just one end so you can "switch" it in and out, provided the voltages are safe enough). My experience has been that there is often a perceptible increase in clarity, particularly if the capacitor being bypassed is a large electrolytic. Everything in the circuit makes a difference, down to the solder and traces themselves. The question is whether or not the differences are significant.... and that can be a subjective matter.
    Of course, if you parallel caps the total capacitance adds up, so there should be an audible difference. Also, I'm not aware of any guitar amps that use electrolytic caps for coupling stages, are you?

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    Quote Originally Posted by hasserl View Post
    Of course, if you parallel caps the total capacitance adds up, so there should be an audible difference. Also, I'm not aware of any guitar amps that use electrolytic caps for coupling stages, are you?
    Definitely found coupling using electrolytics in solid-state bass amplifiers. They can also be found in some consumer audio amps. I don't think it is the increased capacitance so much as the better dielectric which makes an audible difference. Electrolytics have high inductance and resistance at high frequencies.

  9. #79
    Noodle of Reality Steve Conner's Avatar
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    No they don't. Well, some really cheap and nasty ones do, but you get premium low ESR parts.

    I'm designing a DC-DC converter board at work just now, and I'm using some Nichicon 330uf 16V electrolytics that have 14 milliohms ESR at 100 kHz. I believe they're similar to the Panasonic FC series mentioned earlier.

    You pay for it though, they cost about $1.50 each in the small quantities I'm using. That's still pin money in audiophile terms, though. :-)

    On ESL: I once worked with electrolytic caps the size of soup cans, and they had 26 nanohenries ESL. If anything went wrong, they could launch pieces of the circuit over 10 feet. Smaller caps should have proportionately less ESL.

    As far as the importance of ESR/ESL: Depends on the circuit. In a cathode bypass cap, the tube has an internal cathode resistance of its own, equal to 1/gm: somewhat under 1k ohms for a 12AX7. You have to ask yourself what percentage of that the ESR of your cathode bypass cap forms, and whether it'll make 3dB of a difference to anything. You also have to ask how many ohms of reactance the ESL adds to the circuit at 20kHz.

    A guideline given by Douglas Self is: Electrolytic capacitors should never be used as part of RC filters that shape frequency response. The reason being that they have very wide tolerances, and generate measurable distortion if a high audio voltage ever appears across them. They are widely used for coupling in solid-state gear, but they should always be sized so big that they don't roll off in the audio band.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    What's really fun is to make up your own glass plate caps.

    For this you need a large number of thin sheets of glass and a large quantity of tin foil. No, not aluminum foil, *tin* foil. You intersperse one plate of glass, one sheet of tinfoil, and repeat as needed. You leave the tin foil extended out of opposite sides on alternate layers. When you have enough capacitance (easy to calculate how much you have, it's a beginning physics problem), you fold all the protruding tabs on one side down and solder a wire to each of them. Same for the alternating foils on the other side. Now you have a capacitor which will withstand lots of volts, several thousand at least, and which has vanishing small ESL. You can pull some real current pulses out of it, as well as storing a lot of energy in there. The energy stored goes up linearly with capacitance but by the square of the voltage, so things get very charge-y.

    A really good source of thin sheets of glass is the face plates for welding helmets. These are consistent in size and shape, and come in boxes of 100's.

    Glass plate caps like this will hold lethal charges for months or years. They're quite dangerous because the energy storage is so high and the leakage is so low.

    Eh? Heavy and fragile? Not enough capacitance? Pooh. Nothing succeeds like excess.

  11. #81
    Senior Member guitician's Avatar
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    That reminds me of an idea I had to make the cabinet out of dielectric and use it as the PSU filter. I like trying the unusual sometimes, just for fun.

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    Quote Originally Posted by guitician View Post
    That reminds me of an idea I had to make the cabinet out of dielectric and use it as the PSU filter. I like trying the unusual sometimes, just for fun.
    That would certainly make picking which of the leads was the ground lead versus hot lead important...

  13. #83
    Old Timer J M Fahey's Avatar
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    Hi guitician.
    Your idea
    That reminds me of an idea I had to make the cabinet out of dielectric and use it as the PSU filter. I like trying the unusual sometimes, just for fun.
    is neither that preposterous nor that new, since it was used some 4000 years ago.
    Just read your Bible or simply search for "Ark of the Covenant".
    It was a cabinet built of "the driest wood that could be found in the hottest desert", great dielectric (for the age) if you ask me.
    It was covered in gold foil, inside and out.
    It was carried averywhere enveloped in a piece of blue cloth, which must naturally have been wiping it all the time, because of movement, and given the desert conditions must also have been *very* dry.
    Do I hear the phrase "electrostatic buildup"?
    It usually runs into KiloVolts, as the 1/2 inch sparks show.
    No wonder "everybody who touched it died"
    Please be sure that what I state above is written with the maximum respect, and, besides, I am one of those who believe that the Bible *is* based in fact, even if sometimes those who transmitted such facts to us by word of mouth sometimes used different words than what we *might* have used.

  14. #84
    Old Timer tedmich's Avatar
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    Quote Originally Posted by J M Fahey View Post
    No wonder "everybody who touched it died"
    I believe everyone who didn't touch it also died, hardly a miraculous claim.

    Didn't Moses gets all pissed about the Golden Calf and then his followers end up worshiping a golden box? From ROTLA it could hold quite a charge though, enough to melt Nazi's apparently.

  15. #85
    Noodle of Reality Steve Conner's Avatar
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    Quote Originally Posted by J M Fahey View Post
    Do I hear the phrase "electrostatic buildup"?
    It usually runs into KiloVolts, as the 1/2 inch sparks show.
    No wonder "everybody who touched it died"
    I swear this is true! It was originally called "Arcs from the covering", but it got mangled in translation.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

  16. #86
    Senior Member guitician's Avatar
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    Hmm, I always thought of my amps as of being a little divine in nature....

    Organic polymer sheet may work.....now were do I get some samples?

  17. #87
    Senior Member cminor9's Avatar
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    Quote Originally Posted by cminor9 View Post
    I am going to order some spragues, and just for fun, some Solens for my Matchless clone.

    I am no expert as I have only been doing this a couple of years, but I have always been a parts-is-parts person simply for the fact that guys like Jim Marshall and especially Leo fender cared about economics. It just makes more business sense. I cannot see those guys debating the merits of various manufaturers' components. They were running a business. That's my theory and I am sticking to it. So I am what you could call a bit of a skeptic.

    I'll post the results. I ought to record these amps and post them for you all to hear, sort of a before and after thing. The after will be with no changes other than filter caps, so it will be somewhat scientific (though I have no cap tester). Maybe I'll do just that.
    As promised (well, about 25% of what I had wanted to do)... I got a couple of F&T caps and dropped them into my spitfire clone. I replaced Xicon caps of the same value and voltage (well, maybe the xicons were rated for 25v lower, but the amp in question has a B+ of about 350v) No other changes. plugged in, and?

    Didn't notice much if any difference in the overall tone of the amp at normal playing volumes. That's a good thing, cause it sounded fine. The only thing I didn't like was the tone of the amp when driven full tilt. So I cranked it up, and I did actually notice some improvement. It didn't get all muddy and sucky when I hit a bunch of palm muted power chords.

    As for the 6G3 with all four filter caps being Xicons...I didn't work on that one. I'm selling it to someone who really likes it (he begged me not to salvage it and made a 5G9), so I am not really going to mess with it. But that would have been a *really* good test. Sorry, guys.

    So perhaps not a conclusive test in the sense that I did a double blind test, but in my mind it was ten dollars well spent. Really, it comes down to a bit of an edge case: in reality I am not gonna play that amp *that* hard cause I don't play much metal these days (Master and Volume full on.) But if I ever want to, it'll sound the way I like it to.

    Would the Xicons have been good enough? Probably, because this amp isn't being run that hard regularly. It's the 80/20 rule, of which Steve Conner's 3db rule seems to be a corollary: in most cases the 80% is good enough. But it made an audible difference, albeit in an edge case, so I think in this instance I am happy with the results (sometimes, 80% isn't good enough, sorry Pareto.) F&T caps are about $5 apiece for the common 22uf/500V value. I can get Xicons for about a buck apiece. I could pay $8 for spragues. Is $4 extra per cap a lot of money? I don't think so. If I were mass producing amps, it most certainly would be. But for building amps I can gig/record with I am willing to spend a *little* extra in the right places. My next amp will be a 5G9 or a clone of a boutique amp I found a schematic for (though I am grappling with the question of do I *really* need any more amps?) For something like a boutique knockoff or a tweed, if I don't buy one of those CE Manufacturing cans for space reasons, I think I'd do the F&Ts. For recapping my hot rod deville, I'd use the Xicons.

    I wish I had a scope so I could provide hard data. I don't so I can't. This is as good as it gets from me. The bottom line: It didn't make a different amp, but for the edge case I was testing for it helped enough to satisfy me. For $10, the cost/benefit ratio was good enough.
    In the future I invented time travel.

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    Quote Originally Posted by cminor9 View Post
    I replaced Xicon caps of the same value and voltage
    Given that most film caps are either 10% or 5% tolerance, how closely did the two sets match in actual, measured value as opposed to the 10%-20% they could have mismatched and still been within tolerance?


    So perhaps not a conclusive test in the sense that I did a double blind test, but in my mind it was ten dollars well spent.
    I believe that every part of this statement is literally true.

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    Quote Originally Posted by Diablo View Post
    I love this quote from their "specifications":
    Fuses always carry high electric current thereby causing metal fatigue. This would then adversely alter the conductivity behavior of the fuse element and hence the performance of the equipment.

    Well, I'm a metallurgist, and I was never taught that electricity causes metal fatigue, and I never read about that possibility before. So, I guess we should also tear out the wiring inside our house after some period of time because the copper has been fatigued by the electrical current. I think I'll go purchase some stock in the copper mining industry. Maybe we should ask them why their gold plated fuses aren't fatigued by the electrical currents. This is fascinating science...
    You're the second metallurgist I've met. The first one was my old man and his BS is from MIT, class of 1941. He sure knew his stuff-about metals anyway.

  20. #90
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    Quote Originally Posted by R.G. View Post
    Given that most film caps are either 10% or 5% tolerance, how closely did the two sets match in actual, measured value as opposed to the 10%-20% they could have mismatched and still been within tolerance?
    I have no cap tester. I don't know.

    Quote Originally Posted by R.G. View Post
    I believe that every part of this statement is literally true.
    Zing! You're funny, I see what you did there. Literally, it made me laugh. Good one.

    Maybe it is in my own mind. Keep in mind I entered this as somewhat of a skeptic. So while perhaps there is a bit of a confirmation bias in my mind since I did pay money for the caps and wanted them to work, I certainly didn't expect to hear a difference. Perhaps if someone were to reimburse me for the caps, then things would change?

    A double blind A-B test would have been ideal, but then of course I'd need an exact replica of the clone I built (with parts that measure all the same, natch.) Or I could have come up with some complex system of switches to switch the new ones out and the old ones in. Also ideal would have been measuring each cap to ensure they were of the same value, and then viewing the signal on a scope and providing the traces for everyone.

    It starts to get pretty absurd, doesn't it? Even then someone would make the claim that I slightly rerouted some wire or fixed a bad solder joint or heated a component one too many times. That's the way it is with these sorts of things. Believers believe and skeptics doubt, and there's nothing little ole me can do about that. Yes, caps are a holy war.

    I got crap to do and a life to live and certainly not enough time or resources to do a proper scientific test or deal with people's faith in the mighty high-end cap. I just wanted to post my subjective, anecdotal results for everyone to see. I am starting to wonder why, though, see previous paragraph.

    This is why I work in software development. Testing is so much easier. Just write a unit test and execute against the actual code and you're done. No double blind, no subjectiveness. Oh, there are still holy wars (coding style, development methodology, language, platform), but I guess I have the good sense to stay out of them.

    Jeez.
    In the future I invented time travel.

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    Quote Originally Posted by cminor9 View Post
    I have no cap tester. I don't know.
    We run into this with effects a lot. People will try some caps which have the same number printed on them, and come to some conclusion. The brand of cap which sounds better then becomes the Holy Grail Cap, when it's 10% or more different from the capacitance of the UN-holy grail cap.

    Maybe it is in my own mind. Keep in mind I entered this as somewhat of a skeptic. So while perhaps there is a bit of a confirmation bias in my mind since I did pay money for the caps and wanted them to work, I certainly didn't expect to hear a difference. Perhaps if someone were to reimburse me for the caps, then things would change?
    I may have mentioned Clever Hans the horse; I think I did. The problem with any internal bias is that you can't compensate for it even if you know it's there. Every aspect of a taste test matters to the opinion of the person testing; paying for caps, putting them in yourself, time since the last test, color of the cap, every thing. Having read some of the reasoning behind the way psychological testing is done, I tend to err on the side of thinking that a fair test by one person is almost impossible, and not because the person is uneducated, biased, or malicious. Instead, it's because they're human.

    A double blind A-B test would have been ideal, but then of course I'd need an exact replica of the clone I built (with parts that measure all the same, natch.) Or I could have come up with some complex system of switches to switch the new ones out and the old ones in.
    Yeah. The problem with good testing methods is that they're HARD to set up right, and expensive in money, time, or both.

    Also ideal would have been measuring each cap to ensure they were of the same value, and then viewing the signal on a scope and providing the traces for everyone.
    The problem with that is that scope traces don't show you what you hear. Frequency analyzer or Fourier transform spectra come closer. Again, it's hard to do well. This is one valid reason that the hifi tweekos have for not doing proper testing. Not the one they say, but a real one they don't say.

    It starts to get pretty absurd, doesn't it? Even then someone would make the claim that I slightly rerouted some wire or fixed a bad solder joint or heated a component one too many times. That's the way it is with these sorts of things. Believers believe and skeptics doubt, and there's nothing little ole me can do about that. Yes, caps are a holy war.
    You are very perceptive. Once you allow the idea that micro-effects, especially ones that by their nature *can't* be measured (as the hifi tweekos like to say) except by expert and gifted human listeners, the trail of things that can affect the results starts to build. I've seen audio nuts insist that they can hear the difference in identical circuits built on teflon circuit boards versus glass-epoxy. And that they could hear the difference between two copper wires, one of which contained a tiny percentage more oxygen than the other. Yes, it gets absurd.

    I got crap to do and a life to live and certainly not enough time or resources to do a proper scientific test or deal with people's faith in the mighty high-end cap. I just wanted to post my subjective, anecdotal results for everyone to see. I am starting to wonder why, though, see previous paragraph.
    At the bottom of this is the fact that we tinker with things to make them sound better to us. There can really be no disagreement that if something sounds better to you, it sounds better - to you. Good sound happens in the human brain, not in the ears. Just like beauty is in the eye of the beholder. Your anecdotal results are worth as much as anyone else's. Exactly the same, in fact.

    This is why I work in software development. ... Oh, there are still holy wars (coding style, development methodology, language, platform), but I guess I have the good sense to stay out of them.
    That is good sense. I ran a kernel development group for a while, and the religious wars are as vicious there as anywhere.

    What's scary about religious wars is that you cannot win a religious war with true believers. You can only eliminate the true believers on the other side. This bothers me a lot, and not just for musical appreciation reasons.

  22. #92
    Senior Member hasserl's Avatar
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    I may have mentioned Clever Hans the horse; I think I did. The problem with any internal bias is that you can't compensate for it even if you know it's there. Every aspect of a taste test matters to the opinion of the person testing; paying for caps, putting them in yourself, time since the last test, color of the cap, every thing. Having read some of the reasoning behind the way psychological testing is done, I tend to err on the side of thinking that a fair test by one person is almost impossible, and not because the person is uneducated, biased, or malicious. Instead, it's because they're human.
    People get offended when you try to explain this to them, as if you're questioning their ears, their ability to hear, their honesty, etc. They don't get that this is not a matter of those things, but a matter of subconcious reaction to stimulus that cannot be conciously controlled. It effects everyone, I am not impervious to this, nor is anyone else. The only way to objectively evaluate things is to eliminate the subjective. If you don't do that then all you have is an interesting (or not so interesting) anecdote. To make concrete assesments from subjective anecdotes is ludicrous. But that is not to deny personal likes and dislikes, of which we all have many.

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    Quote Originally Posted by hasserl View Post
    People get offended when you try to explain this to them, as if you're questioning their ears, their ability to hear, their honesty, etc. They don't get that this is not a matter of those things, but a matter of subconcious reaction to stimulus that cannot be conciously controlled. It effects everyone, I am not impervious to this, nor is anyone else. The only way to objectively evaluate things is to eliminate the subjective. If you don't do that then all you have is an interesting (or not so interesting) anecdote. To make concrete assesments from subjective anecdotes is ludicrous. But that is not to deny personal likes and dislikes, of which we all have many.
    Edwin Armstrong, the electronics genius, often observed: "It ain't what people know that's dangerous-it's what they know that ain't so."

  24. #94
    Senior Member cminor9's Avatar
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    Quote Originally Posted by R.G. View Post
    I may have mentioned Clever Hans the horse; I think I did.
    Nice! I had never heard of that, I'll have to admit. Interesting discussion about more than just caps here. /. used to be this good.
    In the future I invented time travel.

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    Quote Originally Posted by Steve Conner View Post
    Not only is the emperor naked, but he teabagged you while you were asleep, before riding off into the sunset on Clever Hans. Or maybe it was the head of marketing at Solen who did that, I don't know.

    There's no such thing as "somewhat scientific", an experiment is either scientific or it's not. If you're not prepared to go the whole way and do a double blind test, you might as well take Frank Zappa's advice: "Shut up and play yer guitar"

    I've joked (?) before about forming the "3dB club", of die-hard objectivists who refuse to consider any changes to their equipment that make less than 3dB of a difference to some measurable quantity.

    RG: Here's a picture from an electronics forum I hang out on, that might make you smile.
    Steve...I noticed that in the pic, the larger outside can is rated for 6800uf...the cap that is inside is a mere 2200uf.....somebody is getting taken for a money ride here.....
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  26. #96
    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by bsco View Post
    Steve...I noticed that in the pic, the larger outside can is rated for 6800uf...the cap that is inside is a mere 2200uf.....somebody is getting taken for a money ride here.....
    Steve's been on a self imposed holiday from MEF a couple years now, paying attention to more important stuff like his career. In any case the photo's an example of what you get when you buy bargain basement deals from east Asia. Similar with semiconductors. If a deal is too good to be true, it likely is.
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  27. #97
    Old Timer Tom Phillips's Avatar
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    Quote Originally Posted by bsco View Post
    Steve...I noticed that in the pic, the larger outside can is rated for 6800uf...the cap that is inside is a mere 2200uf.....somebody is getting taken for a money ride here.....
    And also the real voltage rating is 35V Vs. the 50V printed on the outside. Let's call that outside part the explosion shield.
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  28. #98
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    Quote Originally Posted by Tom Phillips View Post
    And also the real voltage rating is 35V Vs. the 50V printed on the outside. Let's call that outside part the explosion shield.
    Never noticed the difference in the voltage ratings...Kind of hard to make out the voltage rating on the bigger can....to me, it is an awful lot of trouble to go through to take a cap apart, change the guts out and seal it up again.....(didn't realize Steve was on extended vacation).......

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    Power Supply Caps - On a 6v6 PP HiFi Amp I found that 60uF/900V Polypropylene "Pulse Grade" sounded much more "relaxed" and powerfull than 100uF/450V Electrolytics. Of-course it was 4 times the size.
    If using Motor Caps make sure you use Motor RUN caps and NOT Motor START caps. The Motor Start Caps are rated for intermittent use ONLY.
    Haven't tried them in a Git Amp but would not be surprised to find similar improvements to what I found in the HiFi Amp.

    Coupling Caps - the caps exhibit their worst distortion as the voltage across the cap reverses, mechanical stress from electric fields try to compress the dielectric between plates and there is some mechanical hysteresis. It is this hysteresis when the voltage across the cap reverses polarity which cuases the most objectionable "warts".
    In most tube amps the coupling cap is a DC blocker and the absolute polarity of the voltage across the cap (DC + AC signal) never reverses and so you don't get that distortion mechanism, you really don't notice any difference between a 50 cent polyester or a 50 dollar piece of audio jewellry. Polypropylene are only a few cents more than polyester so I always use them.
    This bit about coupling caps I noticed particularly in a SS HiFi preamp. The input cap had no DC voltage across it so the really expensive tin foil caps were quite a lot better.
    But after redesigning the input such that there was always a DC level across the cap and the voltage never reversed when the AC signal was applied I found that a $2 polyproylene was as good as the $50 audiophool item.

    So for GIT or HIFI Tube Amps where the voltage polarity across the cap never reverses, then cap choice is not that critical. You probably won't notice the difference between Poyester and polypropylene and the really expensive audiophool stuff is just a waste of money.

    Cheers,
    Ian
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    lol @ "audio jewelry"
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  31. #101
    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by bsco View Post
    t is an awful lot of trouble to go through to take a cap apart, change the guts out and seal it up again.....(didn't realize Steve was on extended vacation).......
    I don't think the counterfeiters go to that much trouble. They just accumulate a barrel full of pulls from wherever they can get 'em, package them in good looking cylinders (blast shields, yes Tom, heh heh... quite right!) slap a plastic cover on then flog 'em to whoever will buy on ebay.

    Steve, as I'm sure you can tell, was a prize member here. Came a time he had to concentrate on his job. Of course it would be terrific to have him stop in just to say hello.

  32. #102
    Old Timer tedmich's Avatar
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    Apr 2008
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    Quote Originally Posted by Gingertube View Post
    If using Motor Caps make sure you use Motor RUN caps and NOT Motor START caps. The Motor Start Caps are rated for intermittent use ONLY

    Cheers,
    Ian
    Often they don't know what they are selling, see here
    LOT OF 50 MOTOR START CAPACITORS CBB60 SH 20uF 240VAC | eBay
    those are 20uF PP film motor run caps, probably good to 500VDC for $0.8 each, and they've sold over 2,000 of them...

    And the motorheads might like to use Italian made Ducati brand caps!
    NEW DUCATI CAPACITOR 10uF 16.17.13EB EN 60252 | eBay



    Last edited by tedmich; 04-05-2017 at 04:44 AM.

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