The truth about caps

[Enzo]

Just an opinion, but I'd be thinking the caps would make more difference than the op amps would. Other than maybe noise.

[cminor9]

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.

[stokes]

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.

[stokes]

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?

[Chuck H]

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

[Enzo]

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?

[JoeM]

..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.

[Chuck H]

Well... I may have to munch on some words. I'm gonna go cut one open right now.

Chuck

[Chuck H]

Yup... Small cap, big can. That's what I found... Yup.

Chuck

[Chuck H]

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.

[dai h.]

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.

[guitarmike2107]

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

[cminor9]

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.

[R.G.]

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.

[Steve Conner]

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.