No sound coming from external speakers, that are plugged into jack on the macbook pro

Given that you changed OS's -- to the linux partition -- and still had the same problem, it sounds like a hardware problem.

If you did damage the hardware, don't worry -- you're not completely screwed. This may be the best excuse to upgrade your audio hardware with an external sound card.

Creative has some great ones that I have used along with Adobe Audition. However most of them are PC only... but in their professional brand (E-MU), they have some great ones for mac.

Creative's professional brand, E-MU is what I currently use. Details here:

• http://us.store.creative.com/0404-USB-2.0/M/B000IXNE3E.htm

Amazon link here:

• http://www.amazon.com/Creative-Professional-0404-USB-2-0/dp/B000IXNE3E/ref=sr_1_1?ie=UTF8&s=electronics&qid=1295028320&sr=8-1

It sounds like a hardware problem in the jack. If you can put pressure on the external part of the plug and change it: cause static or breakup it's probably a hardware problem in the jack.

If you had said you only tried one set of headphones then I'd have said it's probably a problem in the headphone plug but if it's multiple phones and speakers then it's probably the jack.

There's a sensor in that jack that monitors if something's in it or not to switch off the internal speakers. The if there's continuous sound, just switching from internal to external the problem may be that sensor. If the sound cuts out from both internal and external once in a while it's probably the jack.

If the MacBook Pro is still under warranty I'd have Apple look at it, they'll swap motherboard to make it right if it's a hardware problem at no cost to you.