Which Direction To Install Capacitor's Outer Foil

Jason Taylor

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Hi after reading stuff I have a question:

Which way does the outer foil in a capacitor go towards? Does it point to the volume or point toward the tone pot?

I know its not supposed to matter especially with non-polarized caps and all that, but still just wondering which is the theoretical correct way to install a cap.

Outer foil to volume or to tone pot?

Thanks!
 

DavidRamey

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One lead goes to the middle lug of the volume pot and the other lead goes to the outer lug of the tone pot.
 

David Collins

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Outer foil should always be oriented toward Virgo, so plan to change your playing position seasonally. ;)

There are circuits where placing outer foil to the ground side may matter, but this application is far outside of that realm, so there is no such thing as a theoretical correct way to orient a cap in this circuit. Both theoretically and practically, either way is equally correct.

If you wish to follow this simply for peace of mind though, outer foil toward ground, meaning outer foil toward the tone pot. It really doesn't make any difference here though.
 

Jason Taylor

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Outer foil should always be oriented toward Virgo, so plan to change your playing position seasonally. ;)
LOL! I already do that by the way :)

If you wish to follow this simply for peace of mind though, outer foil toward ground, meaning outer foil toward the tone pot. It really doesn't make any difference here though.
Ahhh there's what I was looking for!

What I find EXTREMELY interesting is that on the original Gibbys like the '59s all in this thread... ALL of the oil-filled Bumblebees have the outer foil connected to the TONE pot. As I was waiting for an answer here to my post I noticed this little point!



I think thats very very very interesting!!! All the 1959 Les Pauls using oil-filled Bumblebees have the sealed side outer foil towards the tone pot!

Maybe it DOES make a difference?
 

David Collins

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My guess (admittedly a guess mind you), is that the (entirely made up, yet plausible) story went something like this.

Billy Joe was an electronics specialist had a background education or career in radios. In certain areas of tuned circuits, dealing in megahertz and gigahertz frequencies, there were areas of some circuits where interference on the outer foil could be bled off to ground without affecting signal on the inner foil. So, he was taught or adopted a flat rule of "always connect outer foil to ground".

Gibson starts getting in to electronics, and they hire Billy. Even though now that we're dealing with a circuit where the layout (cap dropped between a 500,000 ohm pot and an 8,000 ohm coil), and frequencies in the hundreds to thousands of Hertz (thousands to millions of times lower than where this actually made a difference), the rule comes along with Billy as something you just always do, and becomes standard procedure.

So that was the rule, a simple one, and they stuck with it. There's really no way that it could make any difference in a circuit like this, as when you're dealing with interference in the tens, hundreds, or thousands of hertz, the outer foil would have to be an inch or two thick to make a lick of difference. At these frequencies, the inner foil is seeing just as much signal as the outer, either by direct induction from the air or from the induced signal on the outer foil.

It's like the story of the Chrismas ham. A mother was teaching her daughter the recipe, when the daughter asked why she was supposed to cut the ham down to 10". The mother was sure it was important to the flavor but couldn't really answer why or how, so she called the grandma and asked "why do we always cut the ham down to ten inches?" She said "I don't know, that's just how my mom taught me to do it". So they called great grandma to ask. Great grandma replied "you're still doing that? We just did that back then because it was the biggest ham we could fit in the old stove!".

In any case, even if it doesn't help in any meaningful way, it most certainly doesn't hurt. Just as easy to put the outer foil toward ground as it is the other, so no harm sticking with tradition.
 

Jason Taylor

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My guess (admittedly a guess mind you), is that the (entirely made up, yet plausible) story went something like this.

Billy Joe was an electronics specialist had a background education or career in radios. In certain areas of tuned circuits, dealing in megahertz and gigahertz frequencies, there were areas of some circuits where interference on the outer foil could be bled off to ground without affecting signal on the inner foil. So, he was taught or adopted a flat rule of "always connect outer foil to ground".

Gibson starts getting in to electronics, and they hire Billy. Even though now that we're dealing with a circuit where the layout (cap dropped between a 500,000 ohm pot and an 8,000 ohm coil), and frequencies in the hundreds to thousands of Hertz (thousands to millions of times lower than where this actually made a difference), the rule comes along with Billy as something you just always do, and becomes standard procedure.

So that was the rule, a simple one, and they stuck with it. There's really no way that it could make any difference in a circuit like this, as when you're dealing with interference in the tens, hundreds, or thousands of hertz, the outer foil would have to be an inch or two thick to make a lick of difference. At these frequencies, the inner foil is seeing just as much signal as the outer, either by direct induction from the air or from the induced signal on the outer foil.

It's like the story of the Chrismas ham. A mother was teaching her daughter the recipe, when the daughter asked why she was supposed to cut the ham down to 10". The mother was sure it was important to the flavor but couldn't really answer why or how, so she called the grandma and asked "why do we always cut the ham down to ten inches?" She said "I don't know, that's just how my mom taught me to do it". So they called great grandma to ask. Great grandma replied "you're still doing that? We just did that back then because it was the biggest ham we could fit in the old stove!".

In any case, even if it doesn't help in any meaningful way, it most certainly doesn't hurt. Just as easy to put the outer foil toward ground as it is the other, so no harm sticking with tradition.
Ha! I hear you. I have no idea why either but just stating something I had observed is all :)

OR.... maybe there's something to the direction Bumblebees are installed after all!

What do others think is the reason Gibson installed them all in a certain direction?
 

rabidhamster

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Some amp builders seem to say they hear a noise floor difference overall by ensuring all the outer foils point towards ground. There's even been amp builds where they went back and did all foil away from, then all foil towards ground.

I say if you can work out which end is the outer foil, you may as well point it towards ground.
 

Jason Taylor

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Some amp builders seem to say they hear a noise floor difference overall by ensuring all the outer foils point towards ground. There's even been amp builds where they went back and did all foil away from, then all foil towards ground.
Exactly thats what I have read as well :)

I say if you can work out which end is the outer foil, you may as well point it towards ground.
As far as Bumblebees I discovered the side with the soldered ending used to fill the cap with oil is the outer foil side.
 

johnh

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Theres a bit of sense in wiring the cap from ground to tone pot, with its outer foil grounded. In a well-wired LP, with pickup covers, grounded pot backs and braided wire, the caps are amoung the very few parts that are not naturally shielded, unless you do it this way!
 

TM1

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All of the old Les Pauls and other Gibson's I've worked on over the last 40 years had the foil side go to Ground. On the old Sprague Bee's, the oil filler spout goes to ground. The vintage Gibson's had the cap coming from the center lug of the volume pot to the outside lug of the Tone pot. The center lug of the Tone pot is grounded. There are exceptions to this as on and off thru the Fifties I have seen the cap wired/soldered to the input lug of the Volume pot(outside lug that the pickup lead is wired to). Volume pots have the outside lug as the input, the center lug as the output and the remaining outside lug is grounded.
Now.. Over the years I have seen some guitar manufactures wire the center lug as the input and the outside lug as the output. This will allow you to roll the volume pot all the way back w/o shutting off the other pickup when your switch is in the middle position.
 

David Collins

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I was looking through some old photos, and in practical terms there really isn't an "outer foil" to speak of. Here's how they were constructed -



As you can see, the foil layers extend equally out on opposite ends, and equally exposed to RFI.

Here's a bumblebee cracked open -





You can see how the whole roll was smashed together when enclosed in the casing -



Then on top of the equal exposure of ends of each foil, if the two layers began at the same length, the outer foil would get shortened as it was rolled, leaving the inner foil extended further out, as you can see if you look closely here.



So we end up with the "outer foil" only covering maybe 2/3 of the circumference, with the "inner foil" ending up as the top metal layer on the remainder. This tiny difference, in an incredibly thin sheet with no real shielding properties, in addition to the equal exposure in all that metal at each end - all in a component specifically engineered to induce a signal in in one side whenever present in the other -

I'm sticking firmly in the "it doesn't matter" camp on this one.

 

Jason Taylor

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I was looking through some old photos, and in practical terms there really isn't an "outer foil" to speak of. Here's how they were constructed -



As you can see, the foil layers extend equally out on opposite ends, and equally exposed to RFI.

Here's a bumblebee cracked open -





You can see how the whole roll was smashed together when enclosed in the casing -



Then on top of the equal exposure of ends of each foil, if the two layers began at the same length, the outer foil would get shortened as it was rolled, leaving the inner foil extended further out, as you can see if you look closely here.



So we end up with the "outer foil" only covering maybe 2/3 of the circumference, with the "inner foil" ending up as the top metal layer on the remainder. This tiny difference, in an incredibly thin sheet with no real shielding properties, in addition to the equal exposure in all that metal at each end - all in a component specifically engineered to induce a signal in in one side whenever present in the other -

I'm sticking firmly in the "it doesn't matter" camp on this one.

But aren't the ends smashed all up together prior to welding the end plate on? I'm so confused LOL!

And what about the fact that there's about 5 feet of rolled up foil we're talking about here?

Are engineers that build these wrong about shielding? Are amp makers wrong about the way they install capacitors?

Is this guy wrong too?

https://www.youtube.com/watch?v=BnR_DLd1PDI&ebc

Let me know David this stuff is confusing! Thanks!
 

Jason Taylor

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Theres a bit of sense in wiring the cap from ground to tone pot, with its outer foil grounded. In a well-wired LP, with pickup covers, grounded pot backs and braided wire, the caps are amoung the very few parts that are not naturally shielded, unless you do it this way!
Sweet thanks for your reply!
 

Jason Taylor

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All of the old Les Pauls and other Gibson's I've worked on over the last 40 years had the foil side go to Ground. On the old Sprague Bee's, the oil filler spout goes to ground. The vintage Gibson's had the cap coming from the center lug of the volume pot to the outside lug of the Tone pot. The center lug of the Tone pot is grounded. There are exceptions to this as on and off thru the Fifties I have seen the cap wired/soldered to the input lug of the Volume pot(outside lug that the pickup lead is wired to). Volume pots have the outside lug as the input, the center lug as the output and the remaining outside lug is grounded.
Now.. Over the years I have seen some guitar manufactures wire the center lug as the input and the outside lug as the output. This will allow you to roll the volume pot all the way back w/o shutting off the other pickup when your switch is in the middle position.
Hey cool and good to know! I think its very interesting that they did it that way with outer foil to ground as well!
 

David Collins

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But aren't the ends smashed all up together prior to welding the end plate on? I'm so confused LOL!

And what about the fact that there's about 5 feet of rolled up foil we're talking about here?

Are engineers that build these wrong about shielding? Are amp makers wrong about the way they install capacitors?

Is this guy wrong too?

https://www.youtube.com/watch?v=BnR_DLd1PDI&ebc

Let me know David this stuff is confusing! Thanks!
Well I'm no EE, and certainly not qualified to say amp makers are wrong, nor would I say an NASA electrical engineer, or computer electrical engineer are wrong either. It's important to note however, that I'm only speaking in the context of passive guitar tone controls, which electronically speaking, is about as distant from amp building as it is from designing circuitry for space shuttles or iPhones. Just important to keep those environments clearly distinct - when talking about passive guitar circuit, references to amp circuits are typically as irrelevant as references to computer circuits.

I did notice something important in the first few minutes of that video though - he was very clear in referring an outer sleeve, separate from the capacitor film layers, as a key factor in describing the outer foil and its effectiveness. If a capacitor is constructed this way, that changes everything and I would say yes, definitely connecting that side to ground in any circuit would be a no-brainer.

The Bumblebee I tore apart in the photos above however, had no such outer sleeve, and the way it was constructed would leave little to no chance that any difference could be noticed with it installed one way or the other.
 

caronte23

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Hey guys, I had seen this video a while back and this guy at some point showed the difference in sound flipping a capacitor around. It actually made a difference :/
Sorry I don't know the science behind it, let me know what you think.
https://www.youtube.com/watch?v=nQcmYvpjx7s
 

Jason Taylor

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The Bumblebee I tore apart in the photos above however, had no such outer sleeve, and the way it was constructed would leave little to no chance that any difference could be noticed with it installed one way or the other.
I am wondering if you might be confusing "outer sleeve" with "outer foil".

If I put a piece of foil against a wall, the side touching the wall is the inner foil.

The side of the foil facing out away from the wall is the "outer foil".

Make sense?

I cant find anything that shows multiple layers of foil...paper...foil...etc.

Looks like a single layer of foil and "kraft paper" to my eyes and what I can find on the internet.

So maybe the "inner foil" is the side of the single layer of foil that lays on the paper, and the "outer foil" is just that... the opposite side.

What say ye?
 

Jason Taylor

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Hey guys, I had seen this video a while back and this guy at some point showed the difference in sound flipping a capacitor around. It actually made a difference :/
Sorry I don't know the science behind it, let me know what you think.
https://www.youtube.com/watch?v=nQcmYvpjx7s
Hey thanks for your reply! Yeah I saw that one too... very interesting!

However, as many many videos have shown, even if the cap has a band marking to show which side of the cap is the outer foil... many times that side is NOT the outer foil side!

So as he discovered which is what my whole thread is about here, is that caps turned the "correct" way will have an impact on tone!

And if the cap is in fact mis-labeled, then the side he may think is the outer foil side may in fact be the inner foil.

BUT IF YOU LOOK CLOSELY at the video... in the beginning the cap band is pointing to the ground on ALL the caps!!!

Only at the end of the video when he is summarizing... for some reason the Cornell cap he points to has now been reversed and the band is pointing the other way!

What happened? I wanna see and hear the difference in orientation LOL!

In addition, when he connects the clip to the Cornell Dubilier, he calls it the Mojo Dijon!

The video I linked in my reply above shows how to figure out the direction of the caps with an oscilloscope :)

I have a feeling though that the Black Beauty is indeed facing the correct way in the video as is the first part with the Cornell... towards the ground to I think its probably installed the correct way. They both sounded good to my ears at least on the video.

What I found interesting the most was when the guitar was still "ringing" as he disconnected the Black Beauty from the alligator clip, the sound of the guitar continued to ring obviously and sustain.

So maybe the caps that he tested showed more than anything what signal and tone is TAKEN AWAY from the full signal of the pickup at all times, even when the tone control pot is turned all the way to 10... because even at 10 the cap is STILL taking away treble from the sound we hear that gets to the amp.

I am one of the dudes that hates the way tone pots load the signal from my pickups when the tone control is on 10... in fact, I make my own "no-load" tone pots so the capacitor is TOTALLY out of the signal path when the tone pot is on 10. My tone pots only work when I roll the tone knob to 9 1/2 or lower.

Make sense?
 

David Collins

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I am wondering if you might be confusing "outer sleeve" with "outer foil".

If I put a piece of foil against a wall, the side touching the wall is the inner foil.

The side of the foil facing out away from the wall is the "outer foil".

Make sense?

I cant find anything that shows multiple layers of foil...paper...foil...etc.

Looks like a single layer of foil and "kraft paper" to my eyes and what I can find on the internet.

So maybe the "inner foil" is the side of the single layer of foil that lays on the paper, and the "outer foil" is just that... the opposite side.

What say ye?
If there is only the capacitive foil layer, there really just isn't any electronically meaningful "outer foil" in the bumblebee I broke down there. In the video referenced, he actually describes the type of "outer foil" he is referring to around the 3:20 mark.

If a capacitor were constructed in this manner, with a separate outside foil jacket fully surrounding the capacitive core layers, that would have potential to act as a shield to at least some limited degree of effectiveness depending on signal strength and frequency. The bumblebees have no such outer jacket as he clearly attributes as being responsible for this effect. With the construction seen in my tear down, orientation becomes essentially irrelevant.
 

David Collins

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Hey guys, I had seen this video a while back and this guy at some point showed the difference in sound flipping a capacitor around. It actually made a difference :/
Sorry I don't know the science behind it, let me know what you think.
https://www.youtube.com/watch?v=nQcmYvpjx7s
Unfortunately, I see the only science demonstrated by this video to be demonstration of the power of placebo effect. There is so much wrong with the methods employed in this comparison, and the specific effects attributed to the caps are so far from any direct effects remotely possible in our dimension.

I'm sure it was a genuine, good willed effort to make objective comparisons, but in the end shows only how easily we can be fooled. The pulsing focused on for example - this is a result of inharmonicity between notes, in the strings themselves as they are played. If there were any tonal properties affected by the caps, this particular phenomenon is absolutely impossible to be among them.
 


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