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Thread: The truth about caps

  1. #1
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    The truth about caps

    Hello all

    I've seen something lately concerning "upgrading" coupling caps and power supply caps. I know Hi Fi guys have strong opinions about such subjects, but I must admit that I am somewhat skeptical. Well, skeptical until I saw a post on another forum by someone I generally think has his head on straight.

    He says he payed to have an upgrade done on a GK rb800 bass head, changining out the OP amps, power supply caps, and coupling caps. He said it does sound better than other similar amps he owns, and others amps he's heard.

    The op amps, I can see. Lower noise spec, higher slew, etc. But caps?

    Now I do understand that there a lot of variables, even in making a heads up comparison, but.....

    So, I am trying to keep an open mind....help me out here. If I change out the caps in my own 800's, will I finally have "inky black soundstage" ?

    Secondly, are any manufacturers know to have noticably better products?

    For example Nichion vs vishay etc, for similar capacitor categories, like power supply alum electros.....

    If there's something to this, I'll give it a try.

  2. #2
    Old Timer defaced's Avatar
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    This is a recent thread that hashes out some of what you're after, particularly toward the end. Capacitors.. which ones for which applications?
    I know your question has been discussed here before, I just can't seem to put my hand on the thread right now.

    And a link from that thread that gives some data and a direct answer to your question.
    Cables, Interconnects and Other Stuff - The Truth

    And in the end, you'll find this is a hot topic with many opinions. I'd say grab some caps and see for yourself.
    -Mike

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    I deal only with tube amps.I can tell you that power supply caps definately make a difference in guitar amps.Coupling caps,not so much,but in some cases they do.Such as,if they are such cheap crap or they are leaky.I learned about tube biasing and filter caps from a local TV repair guy when I was 13,I am now over 50,so I've been doing this a long time.When I do a cap job I give the guarantee that if your caps are 10 or more years old,or they are those xicon or similar asian caps,I put in Sprague or F&T brand and if you dont notice an appreciable improvement in tone and response,I will put the old ones back and you pay nothing.In the past 2 years or so I have done about 100 Boogie amps,mostly via another forum,and have yet to have to put any caps back in.Filter caps have a definate life span,which is determined by various factors,but generally after ten years they are done.You will get many who say"my caps are 40 years old and still work" and they are right,they "still work",but they are not as efficient as they can be,and your amp will definately perform better with fresh,good quality caps.As for the xicon brand and such,I can tell you,I've tried them all over the years and there is a difference.I have done about a half dozen newer Fender Blues Devilles and the like in the last year.Replaced the Nichicons they are using these days,with Sprague and F&T's and the owners were amazed at the improvement,and again,nobody wanted their old caps put back in.I do not do solid state amps for the most part,and I would think that since the power supplies in these amps have lower voltages,and the components are more efficient, the caps may have a longer life span,but i cant say 100%.As for coupling caps,Hi-Fi amps are intended for absolute sound repro,so they look for tighter tolerances and "cleaner" circuitry,so the higher quality coupling caps are desired,guitar amps on the other hand are designed to "color" the tone of the guitar,and if the coupling caps will make any difference is purely subjective.I only recommend changing them if the cap is leaking dc.

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    Senior Member cminor9's Avatar
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    Quote Originally Posted by stokes View Post
    I deal only with tube amps.I can tell you that power supply caps definately make a difference in guitar amps.

    When I do a cap job I give the guarantee that if your caps are 10 or more years old,or they are those xicon or similar asian caps,I put in Sprague or F&T brand and if you dont notice an appreciable improvement in tone and response,I will put the old ones back and you pay nothing..
    Interesting. Can you explain this a bit more? What do these cheap caps in the power supply do? What attribute of the sound is changed with the cap upgrade? I am really, really curious to see what you say about this to see if it lines up with something I have been noticing in several of my builds using various caps (xicon and spragues are among them, and guess which I prefer? The sprague).
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    Quote Originally Posted by cminor9 View Post
    Interesting. Can you explain this a bit more? What do these cheap caps in the power supply do? What attribute of the sound is changed with the cap upgrade? I am really, really curious to see what you say about this to see if it lines up with something I have been noticing in several of my builds using various caps (xicon and spragues are among them, and guess which I prefer? The sprague).
    They cause the bass to go "flabby" when cranked and an amp wont sound as tight with them when compared to the Sprague or F&T's.Amps with these caps are not as "lively",if you will,kind of flat or duller sounding.I've recently had a brand new Blues Jr and a Blues Deville that each had an oscillation problem caused by one of these caps that otherwise tested okay.I've done about a half dozen newer Fenders for people who have heard my mantra over the past year or so,who otherwise had no complaints about their amps and the improvement left them shaking their heads wondering about what they were led to believe by other techs,close to 100 Boogies over the last 2 years or so as well.There may well be other brands that can compare to the Sprague and F&T's,but I havent found them yet.For the longest time I swore by Spragues only,but I found the F&T's live up to my expectations,so I guess there could be others,but for me right now its just those two.I wont use any others.

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    Supporting Member Chuck H's Avatar
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    Filter caps are a double edge sword. Alot of how new filters sound can depend not only on their ESR, but also on how the circuit is effected by the ESR. Consider that a signal of only a few millivolts at the input of an amp will effect the tone. If you have caps with high ESR and the input stage filter shares a ground with the output stage filter it's likely that a few millivolts of signal are riding on the power rail. This can result in NFB and PFB loops that absolutely do effect the tone of the amp, for better or worse. For example, at The Amp Garage where they discuss Trainwreck amps there are several threads about how different filters effect the tone of the amp. Most often the high quality caps make the amp too bright. But they found a way around using cheap caps... Now the cap of choice is a Sozo "replica" cap that is supposedly made the same way caps were decades ago. Since typical aluminum cap impedances were a bit higher decades ago I surmise that these small feedback loops created by higher ESR somehow have a beneficial effect on the Trainwreck Express circuit. This would also partly explain why builders find it so hard to clone that amp without it being too harsh and bright.

    Most of the time I think high ESR is a bad thing though. But I try to keep an open mind. A lot would depend on ground scheme, how many stages, lead length and just generally what might be "talking" to what. And after that, how this effects the tone at different stages or the overall amp. It would be almost impossible to calculate for the purposes of design to exploit this phenomenon, so I try to design for a low ESR and carefully layout my grounds to avoid the issue all together. Then I voice from there. This way I can remove some voodoo from the equation.

    Chuck

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    Supporting Member loudthud's Avatar
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    When I was working on my ultimate bass amp project a few years ago I noticed that you can plainly see a rectified version of the bass guitar signal riding on the B+. The lower the frequency, the bigger it looks. It's hard to see at first because the supply ripple is riding on top of everything. It just looks like a bunch of sawtooth waves bobing up and down until you sync on the bass guitar signal. I installed a PI B+ filter to get rid of most of the ripple. This made it much easier to see the bass guitar signal. Further increases in amount of capacitance were needed to reduce the bass guitar signal on a low E (~40Hz). This increased the clairity of low notes. On a 50W amp with 450V B+ it took about 200uF.

    So in guitar amps I would expect modest changes of capacitance with B+ filters in the 50uF range to be audible. As far as I could tell, ESR didn't come into play. It would have to be pretty bad before you could see anything on the B+ but it would tend to effect all frequencies. If ESR was 10 ohms, you might see 2V of guitar signal hidden by 20V of ripple.

    I suppose it would be easy enough to do an experiment by installing a rheostat in the ground return of a filter cap to judge how bad ESR has to be to be audible.

    How much ESR to these cheap caps have?
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    Supporting Member Chuck H's Avatar
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    Quote Originally Posted by loudthud View Post
    How much ESR to these cheap caps have?
    I dunno. I never use them anymore. Long ago I did compare some cheap Xicon aluminums to the Spragues. The Spragues did sound tighter and there was less "ghosting".

    I remember a hands on trial done by Dai some three or more years ago where he added small (one to three ohm) resistors to the filters to test this. He reported that there WAS an audible difference with even small resistances added. Also, The guy's at The Amp Garage have worked hard on the Express design to try and bring down the myth that only Ken Fischer could build one. They are very critical and not generally prone to lore or voodoo. They are also purists for the most part. So their examination of one particular aspect that amps circuit is something I wouldn't just ignore for lack of test sheets and scope data. Though I'm not inclined to go to the trouble myself.

    Chuck

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    Senior Member hasserl's Avatar
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    There has been lots of information provided in the past few years comparing Sprague Atom caps to smaller, less expensive caps like Xicon, IC and others. Spragues have been cut open to reveal small caps housed inside of the larger outter can. IME we're dealing mostly with subjective likes/dislikes and preferences based on anecdotal evidence and a lack of emperical evidence or controlled comparisons.

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    Senior Member cminor9's Avatar
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    Quote Originally Posted by stokes View Post
    They cause the bass to go "flabby" when cranked and an amp wont sound as tight with them when compared to the Sprague or F&T's.Amps with these caps are not as "lively",if you will,kind of flat or duller sounding.I've recently had a brand new Blues Jr and a Blues Deville that each had an oscillation problem caused by one of these caps that otherwise tested okay.I've done about a half dozen newer Fenders for people who have heard my mantra over the past year or so,who otherwise had no complaints about their amps and the improvement left them shaking their heads wondering about what they were led to believe by other techs,close to 100 Boogies over the last 2 years or so as well.There may well be other brands that can compare to the Sprague and F&T's,but I havent found them yet.For the longest time I swore by Spragues only,but I found the F&T's live up to my expectations,so I guess there could be others,but for me right now its just those two.I wont use any others.
    Interesting. I built a 6G3 using the xicon filter caps, and it has this weird thing that when cranked and I hit a chord, it sounds good for a second and then when the note starts to decay it gets this overtone (I cannot describe it very well I guess) I really don't like. I hate it so much it renders the amp mostly useless for what I built it for: rockin out. It's only on lower notes, the lower I go the worse it is. I don't have a scope, so that's about as much detail as I can give. Maybe that's a ghost note, but it doesn't match the description of ghost notes I have read.

    Here's another bit that points me to the filter caps:
    1) the 6G3 uses 4 of the xicons (with hammond iron, which I had to zener down so I didn't suspect this was normal sag) and exhibits this problem very noticeably.
    2) I *just* built a spitfire clone with salvaged transformers and totally different brands of parts save for the resistors. The filter caps are a F&T can and two of the xicons for the PI and PA, and I just noticed that this amp exhibits the problem ever so slightly when run full out.
    3) My 5E3 uses Chicago Transformers and Sprague filter caps, and sounds perfect when run hard.

    By process of elimination, that's the filter caps.

    These facts plus your post earlier points to the caps as the source of the problem. This might make the difference between my dismantling the 6G3 and building it into something else or keeping it. I figured it was just supposed to sound that way, cause it's not like I can just walk into a music store and play one. But now I think I'll try the caps once I get some cash. I'll certainly report back with results. I appreciate your post, stokes, and had you chosen to mention another brand of filter cap I would have never given it a second thought. This forum rocks.

    Thanks, stokes...and others.
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    Supporting Member Chuck H's Avatar
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    Quote Originally Posted by hasserl View Post
    Spragues have been cut open to reveal small caps housed inside of the larger outter can.
    Please point me to that information.

    Thanks

    Chuck
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    What's your shipping address? I'll send you one.
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    Supporting Member tubeswell's Avatar
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    Quote Originally Posted by cminor9 View Post
    Interesting. I built a 6G3 using the xicon filter caps, and it has this weird thing that when cranked and I hit a chord, it sounds good for a second and then when the note starts to decay it gets this overtone (I cannot describe it very well I guess) I really don't like.
    Hi cminor9

    Is there enough room to replace the caps with bigger jobbies? All those 6G3 filter caps could go to 20uF Spragues I reckon (or at least the reservoir cap and the screen supply cap could). Physical size seems to make a difference (from my own experiments) in keeping flab out.

    Also, the number of stages you are filtering with each cap is important. The furthest (8uF) cap from the power supply on the schematic is actually filtering 3 stages, which may be part of the 6G3s charm, but if the cap there in particular isn't up to the job, then try going to 20uF in there.
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    Good and interesting information!

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    Quote Originally Posted by Chuck H View Post
    Please point me to that information.

    Thanks

    Chuck
    Here:


    There was also one of a cut open earlier version of the Atom, not at all the same caps as before.
    Attached Thumbnails Attached Thumbnails spragueatom.jpg  
    Last edited by JoeM; 11-23-2009 at 06:04 PM.

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    Senior Member Enzo's Avatar
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    Just an opinion, but I'd be thinking the caps would make more difference than the op amps would. Other than maybe noise.
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    Senior Member cminor9's Avatar
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    Quote Originally Posted by tubeswell View Post
    Hi cminor9

    Is there enough room to replace the caps with bigger jobbies? All those 6G3 filter caps could go to 20uF Spragues I reckon (or at least the reservoir cap and the screen supply cap could). Physical size seems to make a difference (from my own experiments) in keeping flab out.

    Also, the number of stages you are filtering with each cap is important. The furthest (8uF) cap from the power supply on the schematic is actually filtering 3 stages, which may be part of the 6G3s charm, but if the cap there in particular isn't up to the job, then try going to 20uF in there.
    I used 3x22uf, and 1x10uf for the filtering. I guess I could try upping the 10uf to a 22uf. Good point though, you are right: that last cap filters a lot of stages. I just figured by that point the power supply was already really filtered that it didn't make such a difference.

    So far the only charm the 6G3 has had is mud, flab, and bad tone when run hard like I intended the thing to be run. Nice trem though! If changing the caps can clean this thing up, then that'd be a pretty big deal for me.

    If replacing the filter caps with better quality ones can remove the lashing sound I hear (my new word for describing it) it'll make me not so skeptical about "boutique" parts. If replacing the two in my already very nice sounding matchless clone can make it sound even better, I'll fully be in the high-quality-filter-cap camp.
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    Quote Originally Posted by cminor9 View Post
    Interesting. I built a 6G3 using the xicon filter caps, and it has this weird thing that when cranked and I hit a chord, it sounds good for a second and then when the note starts to decay it gets this overtone (I cannot describe it very well I guess) I really don't like. I hate it so much it renders the amp mostly useless for what I built it for: rockin out. It's only on lower notes, the lower I go the worse it is. I don't have a scope, so that's about as much detail as I can give. Maybe that's a ghost note, but it doesn't match the description of ghost notes I have read.

    Here's another bit that points me to the filter caps:
    1) the 6G3 uses 4 of the xicons (with hammond iron, which I had to zener down so I didn't suspect this was normal sag) and exhibits this problem very noticeably.
    2) I *just* built a spitfire clone with salvaged transformers and totally different brands of parts save for the resistors. The filter caps are a F&T can and two of the xicons for the PI and PA, and I just noticed that this amp exhibits the problem ever so slightly when run full out.
    3) My 5E3 uses Chicago Transformers and Sprague filter caps, and sounds perfect when run hard.

    By process of elimination, that's the filter caps.

    These facts plus your post earlier points to the caps as the source of the problem. This might make the difference between my dismantling the 6G3 and building it into something else or keeping it. I figured it was just supposed to sound that way, cause it's not like I can just walk into a music store and play one. But now I think I'll try the caps once I get some cash. I'll certainly report back with results. I appreciate your post, stokes, and had you chosen to mention another brand of filter cap I would have never given it a second thought. This forum rocks.

    Thanks, stokes...and others.
    This sounds to me like filter cap issues.I have seen different noises that you may not think were caused by filters cured by using good quality caps.Another consideration when building or changing filter schemes,is not to use too big a cap for the preamp stages,or adding an additional cap in a circuit that uses one cap for two pre stages.I experimented with a 5E3 by adding an additional cap for the first stage and even with Sprague caps it was not good.This was an amp I built back in the '70's when I had an old designer from RCA coaching me and he explained that "decoupling" the pre from the PI was causing the problem.He gave me a very technical explanation for it at the time,too long ago to remember,and not being or having any hope of being an engineer it escapes me now,but I remember the lesson well.The symptom was a clangy,metalic under tone.I am a proponent of using larger than original caps in the main and screen supply,but leave the pre stages at the value they were designed to use.In the case of your 6G3,I would suggest a 40uf for the first 2 and leave the PI at 16 or 22uf at most and the pre an 8 or 10uf.These amps were designed at a time when Leo wasnt expecting the player to crank the amp so the 16uf just aint enough to keep up when you crank it,IMO.I am sure the better quality caps will ahve your amp sounding better.

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    Quote Originally Posted by hasserl View Post
    IME we're dealing mostly with subjective likes/dislikes and preferences based on anecdotal evidence and a lack of emperical evidence or controlled comparisons.
    I gotta disagree with you there.I started this discussion over at another forum a couple of years ago and over the last two years have been inundated with cap jobs and have made believers in every case,including a couple of hard headed techs who have come to realize that it isnt a purely subjective matter.I have had guys argue that the spec sheets show that the xicon or whatever are just as good or better on paper,IME it just aint so.What works on paper or in the lab doesnt always hash out in practical use.I have heard that Sprague isnt as good as they were in the old days from guys who work in the field,but I havent experienced it myself,at least with the Atoms,I dont use the others,so I cant speak for them.I do have a fresh supply of 30uf/500 Sprague Atoms as well as some older ones I am going to cut a couple open to see about the smaller cap in the big package thing,but I have to wonder what they would benefit doing this.I wish I could get a smaller 30uf/500 Sprague Atom at times,so what would be the point of decieving us by putting a smaller cap in a big wrapper?

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    Supporting Member Chuck H's Avatar
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    At the risk of upsetting some people, that's only a photo. Why, do tell, would someone cut open one of those caps in the first place? Seems to me like the old Bob and Doug Mckenzie trick with the mouse in the beer bottle. Not to mention the fact that anytime a particular 'anything' becomes the item of choice fakes hit the market.

    So, why would someone cut open an electrolytic capacitor? That question alone makes me wonder if it's true. And then, if there are "Sprague" caps out there with little caps inside bigger cans, how do we know their not fakes made to take advantage of the Atom trend.

    I remember when the movie Rambo came out there was a Rambo action figure. At the flea market in San Jose Ca. (where lots of Chinese knockoffs of almost anything are sold) there was a guy selling bogus Rambo action figures. There was also a hispanic "Lambo" for the little latino kids, and a black one called... Can you guess? Sambo! I could have died laughing because if you saw the setup you would know it was just a bad mistake. It was just funny at the time, but I should have bought ten of them. I could probably sell them on Ebay for a fortune.

    Chuck

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    Senior Member Enzo's Avatar
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    SOmeone would cut one open to see what he was getting. If I recall correctly - and that is always a gamble - Bruce Collins was one who did that. And found exactly what is in the photo. SOmeone who uses a ton of caps would want to know he was paying the extra money for actual premium caps instead of the company's plain old caps repackaged to appeal to the retro crowd.

    Just as someone would bust open a sample power transistor from a new order to make sure they were real.


    And then if we want to start thinking gee maybe these are fakes of fakes... and on and on.

    Kinda makes you want to cut one open yourself, donit?
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    Quote Originally Posted by stokes View Post
    ..so what would be the point of decieving us by putting a smaller cap in a big wrapper?
    From what I've read, there was some sort of physical size compatability issue with some equipment. But I dont think you can call that deception. It's funny how many get upset over the photo though. I dont really believe there's any magic in the Atom caps that any good E-cap wouldn't have.

    Bruce Collins mentions having problems with the newer stock Atoms.

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    Supporting Member Chuck H's Avatar
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    Well... I may have to munch on some words. I'm gonna go cut one open right now.

    Chuck

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    Supporting Member Chuck H's Avatar
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    Yup... Small cap, big can. That's what I found... Yup.

    Chuck

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    Supporting Member Chuck H's Avatar
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    FWIW I just built some prototype amps last year that are designed to be run wide open. I did use Atom caps because they have always performed for me in the past. I haven't had any problems with hum or ghost notes. But if you look at the current prices for Atoms in the new Mouser cat you'll see that the most popular values/rating ones have gone up in price... Again. I thought they were too expensive. I used them because they were modestly priced and I knew they wouldn't give me any trouble like I've had with Xicons in the past. But the new high price is a real deterrent for me. Not the small cap in a big can thing so much. Maybe it's time to try some Nichicon's. They look REAL good on paper and cost less.

    Chuck

    P.S. To get this thread back on track... I have built the same amp with Mallory 150 metalized polyester caps for one and Sprague 715p polypropylene for another. They sound different. Not extreme. But there is a definite flavor and vibe difference that I think most players would notice and have a preferencial opinion on. I do think construction matters as much as the materials. Lab testing be damned.

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    Quote Originally Posted by Chuck H View Post
    at The Amp Garage where they discuss Trainwreck amps there are several threads about how different filters effect the tone of the amp. Most often the high quality caps make the amp too bright. But they found a way around using cheap caps...
    hi Chuck, (sry for the inconvenience but) could you direct me to the thread?

    I remember a hands on trial done by Dai some three or more years ago where he added small (one to three ohm) resistors to the filters to test this. He reported that there WAS an audible difference with even small resistances added.
    I think it was actually the opposite (if my memory isn't failing me, lol). A good thread to find would be the one where R.G. mentions some stuff about adding series R to simulate ESR. Completely blanking on the value range he mentioned (50-100ohms??) but should be in the archives somewhere. As far as my personal experimentation I think trying a film in place of an electrolytic seemed more audible than the tiny series R(maybe too tiny to have an effect??).

    IMO there is something (i.e. some actual effect) but whether it's worth it or not probably depends on the situation and people. Whether they can hear it, whether they care to spend the time, money, effort to change and try stuff, voicing of the amp, and whatever else. On my LCR meter FWIW, an alu electro can measure different at diff. test freqs. For example, I bought two BC components (used to be Philips) 250(or220)uF caps, and they measured more at 100/120Hz than 1kHz(somewhere around 210uF vs. 150uF). Some 1uF 50V(Rubycon?--just ordinary ones) were around .68uF at 1kHz but about 1uF at the lower freqs. But some were about the same capacitance (some 10uF100V removed from the input of my Tascam 488mkII). I've got a bit of an obsession with ceramic caps going for a little while, and what I've found reading, measuring is that some of the non-temp. compensating types can change value with application of voltage (DC and AC), also lose cap. over time, have poor tolerances, etc., so there can be real technical things going on. But some of the ones that might be considered technically poorer might be the better sounding, so I think that situational and subjective aspects shouldn't be ignored or not be considered.

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    Interesting thread…

    Perhaps putting the smaller cap into a larger wrapper will extend the life of the cap by keeping it cooler? That’s a poke BTW.

    Amp building/modding is full of the “emperors new clothes effect”, If you mod somebody’s amp and tell them it sounds
    much better they will probably believe it sounds better, until it is blatantly proved that it sounds the same.. good tone is so subjective anyway

    I bet if you didn’t mod it and told them you had modded it, and then played for them but louder than they would normally play it you could probably fool some people.

    But after saying that I am all for modding to get rid of “strange ghost” sounds or to improve the power supply’s handling of low frequencies
    or changing speakers and OT’s or using methods to reduce/noise hiss as these do make big differences in perceived tone… I don’t think I
    will ever go and change out all the coupling caps in an amp just to improve tone and have the mojo . unless the amp was really needing an entire overhaul…

    I think if you are going to go for the best Quality caps you can afford then you had better go the whole hog and get the best quality trannies and everything else..

    JMHO

    Mike

  28. #28
    Senior Member cminor9's Avatar
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    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.
    In the future I invented time travel.

  29. #29
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    Tee hee!

    I can think of several reasons for a smaller cap to be inside a bigger can. One of them would make an MBA proud - fewer outer can sizes to mess with. Instead of making a special outer can in 1/32"/1mm increments, one only needs to make a few sizes, and then stuff the rolled-up can into the next size it fits. Fewer clamps/endcaps/etc to stock.

    I can also think of some reasons why the insides would be smaller than they used to be - advance in electro cap chemistry and materials. Capacitors today *are* smaller than the used to be. A quick read through capacitor literature will turn up terms like "ultrapure foil" and "deep etched foils" and "advanced electrolyte". This has let cap makers put ever-more CV product (the figure of merit for many caps) in a smaller volume. But if you have an existing product you have improved, that would fit in a smaller can, you might not want to upset buyers who are buying the older ones by changing can size on them because big electro caps are a factor in the mechanical setups. Certainly you don't want to force your continuous buyers to make a new decision on which caps to buy. If you make them buy your smaller caps, they'll also quote the competitors too.

    In terms of electrical performance, there is capacitance, ESR and ESL. Dielectric absorption is a very dark horse, distant fourth effect, and there are good reasons to think that DA is not an issue in selecting between caps in the same insulator family - largely that mylar is mylar, polypro is polypro, aluminum oxide is aluminum oxide, and so on. If there's a difference in electros it has to be somewhere, right? Could be ESR, could be ESL, could be actual capacitance, could be in the WIRING from cap terminal to the foils. This last is what made four-terminal caps popular in the low-ESR switching power supply industry. The output DC does not have to share the current path with the input recharge spikes. It seems to me that these are the places to dig.

    In summary, without making any specific comment on capcitor effects being real or not, it seems that if one wants to know, one would do some testing.

    1. Are capacitor tone differences real (i.e. objective) or not (i.e. subjective)?
    If they're real/objective, there is something, somehow that can measure them. If they're subjective only, they only happen in the minds of the people listening, and cannot be measured by any test on the equipment.

    The big problem here is that to do this test, you have the quite-complicated task of figuring out how to separate out whether people consistently hear a difference or not. This is NOT as easy as before-and-after listening, because the human mind is the most complicated thing in the known universe. It does a lot of things, most of which it's not consciously aware of. For an example google "Clever Hans".

    The testing has to be set up in a way that prevents the listener(s) from having any information about what instance they're listening to, whether it's the stock or modified unit. Even then, the test has to be whether the listener can identify the modified from stock unit at a better rate than random guessing. And the person administering the test had better not have any idea which is being listened to for which test (see "Clever Hans" for why) or they can invalidate the test.

    Yes, this flies in the face of "I know what I like and it sounds better X way." And that's true - to the listener's mind. If a listener says "it sounds better this way" and is not consciously lying, then it's an absolutely true statement. It does sound better - to them. Even if there is no difference inside the unit, and famously, even if the unit is completely unchanged. The listener, if a player of an amp, may even play better for thinking the amp is better somehow. Those stories about this situation are conceptually true.

    2. If they're real/objective, what are they and how do you measure/adjust them? Seems like a short time with some resistors and inductors would fix that one pretty well.

    The testing, unfortunately, has to be as rigorous as for 1 to find out whether you made a real difference. But if you ever can separate out what objective, measurable difference actually made a difference in listening by doing a double blind test, you have some hope of dropping the double blind testing and measuring the effect with test equipment, moving it from psychology experiments into electronic design. This is a whole lot easier and simpler to work with. But advertisers *hate* it.

  30. #30
    Noodle of Reality Steve Conner's Avatar
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    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.
    Attached Thumbnails Attached Thumbnails chinese-electrolytics.jpg  
    bsco likes this.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

  31. #31
    Senior Member cminor9's Avatar
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    Quote Originally Posted by Steve Conner View Post
    There's no such thing as "somewhat scientific", an experiment is either scientific or it's not.
    I would be only replacing filter caps. I wouldn't be in the amp replacing anything else. That's a fairly controlled experiment, isolating the thing being tested. The somewhat comes in because there would be no way to know for sure that the caps were exactly within tolerance, since I lack a cap tester. And the act of soldering could reflow some solder around a resistor that was never soldered in good to begin with. Or opening the chassis could let the gremlins and aethers out. Hence the phrase somewhat scientific. It's somewhat scientific in the same sense that many scientific experiments are "somewhat" scientific. It's not hard to imagine that even some laboratory experiments have variables that are unmeasurable, or maybe has variables that people don't even know they need to measure. Did you know that all of the tachyons and neutrinos streaming through the atmosphere make lab rats develop cancer? Neither did I! Maybe I shouldn't have used "somewhat" as a qualifier. I should have said it's as controlled of an experiment as is within my current capabilities. Perhaps you could do better since you probably have better equipment.

    Having six caps across two amps sort of minimizes the possibility of a bad cap. One cap, sure. But one bad cap in each amp? A lot less likely. Not impossible, just less likely.

    I totally agree with your 3db rule. Thing is, I am about ready to tear down my most troublesome and therefore most time consuming build cause it sounds like CRAP because of a very specific tonal quality. I don't care how many decibels of difference it makes, the amp either sucks or it doesn't. If it still sounds like crap I'll never pay more than $2 for a filter cap and tear that MF apart. If $15 worth of new caps removes the specific and identifiable quality (to me; but I'd bet you can hear it. Taking a few days off, I might record it and share) then it's money well spent, cause my time will have been saved. Either way, I'll learn something, and that's worth the money to me.

    I don't need to do a double blind test. I am not an audiophile who wants to believe; if anything I am pretty skeptical. Part of me wants to try this and be able to laugh off people who buy into premium cap snake oil. The other part just wants the stinking 6G3 to be worth all the time and money I put into it, so I can justify spending a few bucks before giving up on it as a lost cause. Like I said, if I still hear the bad sound I am tearing the thing apart and never buying anything but cheap filter caps. It's just that stokes mentioned something very specific, and he has generally in the past been very helpful and knowledgeable. I won't dismiss his opinion as quickly as I might dismiss that of some n00b.

    And were it not for the fact that I can hear the same problem, only much less so, in an amp that has two of its four filter caps from the batch of xicons I bought, I know it's not just that I messed something up in the build. More xicons == more crappy butt-tone.

    Quote Originally Posted by Steve Conner View Post
    you might as well take Frank Zappa's advice: "Shut up and play yer guitar"
    And yes, I can't wait to get this done so I can go back to spending my time practicing. Got some more jazz trio gigs coming up, and I *really* need to focus on those.
    In the future I invented time travel.

  32. #32
    Supporting Member Chuck H's Avatar
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    Dai, if you go to The Amg Garage "Trainwreck Discussion" and search "sozo" you'll find some stuff. Most of it is Geetarpicker (Glen Kuykendal, is that how it's spelled?) pioneering the mods and discussions following. I didn't find the exact thread I remember, but I found enough similar info to fill in. It is definitely eluded to that the higher ESR is thought to sound better in the Express clones.

    I also searched the archives for your old thread but came up dry. I did find a thread where you put R.G.'s 47ohm series resistor to the test. You reported a definite difference there. Both better and worse depending on what a player might want. I also found a lot of stuff where you and I are discussing ESR, series vs. parallel caps, etc. It seems we've been down this road before. Too bad my memory can't reach all the back to the last epoch when it all happened.

    Steve, It's interesting that in your photo the smaller cap is a 2200uf and the huge can they stuck it in says 6800uf. Not only does this seem like shinanagins but it looks as if it may have been ill chosen or factory second parts used to do it. And who can measure 6800uf anyhow to know if it's off? I can't do it with my DMM.

    Chuck

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    I thought the truth about caps is that they are 2 conductors separated by a dialectric.

    Sorry, carry on.
    ST in Phoenix

  34. #34
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    Quote Originally Posted by Phostenix View Post
    I thought the truth about caps is that they are 2 conductors separated by a dialectric.
    Almost. They are two conductors and a dielectric designed to separate the buyer from his money in many circles. In those arenas, knowing what a capcitor is and does is a positive detriment to selling the magic goods.

    Magic capacitors - and resistors, and wires, and insulation, and, and, and - may look ordinary outside, but the insides are filled with pure unobtainium.


  35. #35
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    Quote Originally Posted by R.G. View Post
    ... but the insides are filled with pure unobtainium.

    Hey, the nut on my PRS is made of that, too! Audiophile Grade Guitars. I like the sound of that.

    Ha! Sound of that....

    I'm a little punchy tonight.
    ST in Phoenix

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