A lot of you may not be aware of this!? For argument sake.. Yes, I know this is not exactly positive and negative polarity but more having to do with impedance... Never the less, very dramatic differences!
Easy way to check your caps
Yeah, if you hold onto small value caps, nothing either end, while playing.
http://www.blueguitar.org/new/text/threads/from_adam/components/mallory-outer-foil.pdf
another link http://www.aikenamps.com/index.php/where-to-connect-the-outside-foil-on-capacitors (http://www.aikenamps.com/index.php/where-to-connect-the-outside-foil-on-capacitors)