Opinions.....outside foil

[trem]

This question is Just In Regards to physical location.....not if/if not there is an audible difference.

Is this video correct.?
Plug a TS connector into the amp input...try the cap both ways... when it it "loudest", that means the Outside Foil is connected to the tip of the jack.?
Thank You
(not sure why the pedal is necessary, the cap IS louder one way than the other if you squeeze it between your fingers.)

https://www.youtube.com/watch?v=1f-LdpJiAk4

[DrGonz78]

Yeah interesting topic and the pedal, as far as I know, is not necessary. I like this one video I saw recently...

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

[nsubulysses]

The vid Gonz posted is good. Lots of people talk about what way to do it but I've never seen anyone just literally show on a piece of test equipment like that.

[g1]

Yeah interesting topic and the pedal, as far as I know, is not necessary. I like this one video I saw recently...

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

Someone posted this on another forum, so I'll add the same comments here:
it doesn't really matter outside of the RF world
none of the major amp manufacturers pay any attention aside from polarized electrolytics
most of your favourite tunes were played on and recorded with gear that had a mix of "forward" and "backward" caps

[trem]

Someone posted this on another forum, so I'll add the same comments here:
it doesn't really matter outside of the RF world
none of the major amp manufacturers pay any attention aside from polarized electrolytics
most of your favourite tunes were played on and recorded with gear that had a mix of "forward" and "backward" caps

Not that I am qualified to comment, but...that has been my understanding as well. That is why we shield the "open side" of a chassis against a piece of metal (I buy big aluminum cook pans from the dollar store), so that any RF from the outside world does not mingle with the amp circuit. And.....if the amp lead dress is layed-out well, there wont be any AC floating around to contaminate the guitar signal path.
BUT.....if the caps ARE marked, you have to install them into the circuit, so why not install them the "correct" way.?
Anyway.......like I said, my question is about How To Identify the outside foil.
For you guys that do, what method do you use.?
Thanks

[Enzo]

When I build something I make sure all my resistors face the same way, so color code reads front to back in all or whatever. And the caps I make sure to mount so all have the print on the same side. Just me being anal. As to outside foil, I don't care at all other than if the print faces the right way.

[trem]

That is how I have "always" done it also. I chose a method, and made sure all the parts looked the same.
I have never worried about the outside foil, it probably Is Not Audible in a guitar amp. I was just wondering if there is a legitimate way to identify it, if the cap is not marked.

[überfuzz]

When I build guitar amps I tend not to think HiFi...

[pdf64]

My take on the topic is that it's probably beneficial to some degree to check the cap types used in a build for this, and to then consider it when laying out the build; like an extension to good lead dress.
As every implemented schematic will inevitably have an overlay of capacitances linking everything together, and it's as well to make sure that the benign ones (usually to ground) are likely to dominate the troublemakers (those liable to cause crosstalk / instability).
And from that, for production units, to achieve good performance consistency, it makes sense to ensure that they're all laid out the same.

[Jazz P Bass]

Inside the capacitor the working force is an electrostatic charge.

Why would the charge care where the 'foil' was placed.

If it was even a slight issue, wouldn't the datasheets indicate this?

[DRH1958]

Here is what Randall Aiken has to say on the subject: Where To Connect the Outside Foil on Capacitors Very interesting. Makes total sense. Read all of it, especially the last paragraph. I guess it's one of those "he said, she said" subjects that are part of the amp world.

[g1]

I'm sorry I lead this thread astray into the area trem was specifically trying to avoid (whether foil orientation matters).
His question is how you determine which is the foil end when the cap is not marked.
So please address the method aspect of the question.

I'll directly quote the above linked Aiken article so others can read and comment on it or any other methods for determining foil end.
(from Where To Connect the Outside Foil on Capacitors)

"If the capacitor has no banded end, the outside foil connection could be on either end, so there is no easy visual method to determine the best orientation of the capacitor. However, if you have access to an oscilloscope, you can do a simple test to determine which is the outside foil terminal. Set the scope up to the most sensitive vertical scale (20mV or less, preferably) and connect the scope probe across the capacitor (ground to one side of the cap, probe tip to the other). Grab the capacitor tightly with your fingers, and note the amplitude of the induced 60Hz AC signal (or 50Hz if you are on the other side of the pond). While still holding the capacitor tightly, reverse the scope leads and you should see a dramatic difference in the amplitude of the induced AC signal. The orientation with the lowest induced signal is the one you want, and the ground lead of the scope is connected to the outside foil in that position. Mark it, and connect that side of the cap to the lowest impedance point in the circuit, typically the driving source plate when used as a coupling cap, or the grounded end if used in a shunt position. If you cannot see a large enough induced AC signal by holding the capacitor between your fingers, place the capacitor on top of an AC line cord (that is plugged into the mains wall socket, of course!) instead of holding it between your fingers and you will see a larger signal on the scope. If you are new at this, start with a 0.022uF cap or thereabouts, as it is easiest to see the difference between the two orientations. The induced signal is smaller at 60Hz with larger value capacitors, and is more difficult to see on the scope.

In the case of some types of capacitors, such as ceramic disks, multi-layer ceramics, or silver micas, there is no "outside foil", because the capacitor is made of a single-layer, or stacked layers of dielectric material and conductor. The orientation of these capacitors makes no difference. Also, some higher-voltage film caps (typically the 1000VDC/450VAC and higher values, such as the Orange Drop 716P high-voltage units) use a "series-wound" technique that has two separate sections, side by side, with a common "floating" connection layer, usually at the bottom of the layer stack. These caps will have no inherent shielding either."

[trem]

I tried doing that.....with a scope...on several Mallory 150, and with a few of the Dijon Caps that Mojo sells. I could not see any difference at all.
I squeezed them with my fingers, and I grabbed the AC cord from the bench light, and applied that to the center of the cap also.....nothing I did induced any kind of "noise" .....

[GainFreak]

I tried couple of times to determine the outside foil of 715 series ODs and the scope method didn't work for me either.
What I did is connect the cap to the input of a power amplifier, crank the volume to max and touch the cap with my fingers.
This way I could hear the difference but it's not much. All those guitar amp manufacturers using ODs testing thousands of caps?
I don't think so. Boutique stuff is another thing.

[trem]

I tried couple of times to determine the outside foil of 715 series ODs and the scope method didn't work for me either.
What I did is connect the cap to the input of a power amplifier, crank the volume to max and touch the cap with my fingers.
This way I could hear the difference but it's not much.

Yeah, and that is (basically) what that guy is doing in the video I posted. I tried doing what he is doing (without the fuzz) and I definitely hear a difference when I swap ends.