Capacitor Outer Foil Test

[samato]

I've been reading up on this.  I want to take advantage of any noise rejection I can get by properly orienting the non-polarized caps in my build.  I think I'm clear on which way the outer foil should go in the circuit but I'm not sure I understand how to determine which side is the outer foil.  I read the Aiken stuff and saw the YouTube video with the little box but it's still not clear to me.  Here is how I think it's supposed to be.  Please tell me if I am right or wrong.  I have a 50/50 shot.  

One end of a guitar cable is plugged into an amp and the amp is on.  On the other end of the guitar cable I clip one side of a capacitor to the tip and the other side of the capacitor to the sleeve.  I grab the capacitor between my fingers and listen to the noise level.  Then I switch the capacitor around so the side that was previously touching the tip of the guitar cable is now touching the sleeve and the side that was previously touching the sleeve is now touching the tip.  Again I grab the capacitor between my fingers and listen to the noise level.  

I may need to hold an AC source like a lamp cord to the capacitor to create enough noise.  If so, I do this both times.

The side of the capacitor that makes the least noise when touching the tip of the guitar cable is the outer foil.

Yes?

[Willabe]

http://www.soundgaragetales.com/

samato,  try this.  I was unable to get the exact link page but, it's in there. Look for "cap. be quite". It's on U Toob.

Go into "Garage TV", it's top of the list. I've been wanting to make one of these myself. 


    Brad      

[Raybob]

...

The side of the capacitor that makes the least noise when touching the tip of the guitar cable is the outer foil.

Yes?

No.  Connect both hot and ground to the capacitor.  Hold the cap in your fingers.  Then reverse the leads on the cap.  Then hold the cap in your fingers.  One way will be much louder then the other with your fingers on the outside of the cap.  The loudest noise means you have the outer foil now connected to the hot, not the shield of the guitar cable.  Best to hear the smaller values with treble turned way up.

[FYL]

I was unable to get the exact link page but, it's in there.

Here: http://www.soundgaragetales.com/amp-building/outside-foil-capacitor

And don't forget Randall Aiken's page: http://www.aikenamps.com/OutsideFoil.htm

[samato]

So to make the statement in my original post correct I just need to change the word "least" to "most", right?

The side of the capacitor that makes the least MOST noise when touching the tip of the guitar cable is the outer foil.

If that's it then I get it.  Some of these responses make me think I'm still missing something.  As I said I've read the Aiken stuff and seen the Sound Garage thing.  I don't want to build a box.  My test seems like it would work fine. 

[Raybob]

So to make the statement in my original post correct I just need to change the word "least" to "most", right?

The side of the capacitor that makes the least MOST noise when touching the tip of the guitar cable is the outer foil.

If that's it then I get it.  Some of these responses make me think I'm still missing something.  As I said I've read the Aiken stuff and seen the Sound Garage thing.  I don't want to build a box.  My test seems like it would work fine. 

It's not the sound when you touch the tip.  Connect the tip with a clip wire to the cap.  Then put your fingers on the cap and see if it adds hum.  Then reverse the leads and try again.  The most hum is heard when the tip is connected to the end connected to the outer foil.

[Tone Junkie]

Just needed to bump this up.

[Travst]

The above is correct, it's very easy.  Here's my low-buck version of Gabi's tool:



Hmph... now I remember what I did with the on-off switch I was looking for the other day. 

[Fresh_Start]

John - I like that rig!  Why do you need the switch though? 

Come to think of it, how about this approach: stick a plug in your input jack, assuming it's a switching jack.  Turn Volume (1st one) down to "1".  Attach one jumper to the input jack tip and another jumper to ground.  Clip other ends of jumpers to cap, turn up Volume a little, and test with fingers.  Volume down, flip & repeat.

Anything wrong with that process?

Chip

[samato]

John - I like that rig!  Why do you need the switch though? 

Come to think of it, how about this approach: stick a plug in your input jack, assuming it's a switching jack.  Turn Volume (1st one) down to "1".  Attach one jumper to the input jack tip and another jumper to ground.  Clip other ends of jumpers to cap, turn up Volume a little, and test with fingers.  Volume down, flip & repeat.

Anything wrong with that process?

Chip

That's how I did it.  For a while I thought maybe I was doing something wrong because some of what I've seen/read make it sound like you need a box like that.  I wanted to build an amp, not a box for testing caps.

[Travst]

The switch on the right reverses polarity so that I don't have to manually flip the cap around.  The other switch turns it off and on.  It's not really necessary.

I don't want to tell you what the wife said when she saw what I'd done with her Tupperware.  

[Fresh_Start]

Ahhh - the polarity switch is a neat idea.

Your wife's comments couldn't have been as bad as the time my mother came home early and discovered that Pyrex vessels are excellent for soaking motorcycle parts in kerosene for cleaning... in her kitchen.  It was really cold outside that day!

Chip

[phsyconoodler]

I don't want to tell you what the wife said when she saw what I'd done with her Tupperware.  
[/quote]

Better than leftover meatloaf.

[Willabe]

Better than leftover meatloaf.

                                   


      Brad     

[Tone Junkie]

Thats funny when I bumped this up so I wouldnt loose it, i never thought I would get a great picture of a tool I need to build, wifes in the kitchen so i will have to wait awile before sneaking off with her tupperware.(LOL).
Bill

[Willabe]

OOOHHH, Your gonna get in trouble.         


         Brad           

[Travst]

Tupperware works great for aging guitar parts as well:



I asked beforehand that time.

[navdave]

Wow you learn something new all the time. Never gave much thought to cap orientation.
I like building high gain amps so this comes in very handy. It would be cool to build two
identical amps one with outer foils going the correct way the other all reversed,
just to see how much noisier the the reversed one would be. 

[samato]

Wow you learn something new all the time. Never gave much thought to cap orientation.
I like building high gain amps so this comes in very handy. It would be cool to build two
identical amps one with outer foils going the correct way the other all reversed,
just to see how much noisier the the reversed one would be. 

I would be very interested in the results of a test like that.  I think it would be better to use the same amp and flip the caps.  You'd have to make recordings of each way and be very careful to use the same guitar, cable, settings, etc. both times.