Thanks for the help, it it working very well testing with just a speaker and the jack. IF you would have time for one more question, I would appreciate it.
For the actual project I am working on, I am using a breakout board from Sparkfun to amplify my speaker https://www.sparkfun.com/products/11044
. It's a great little board and it is working wonderfully. I am using a little 0.4W 8oHm speaker and the breakout board for amplification as I have a very confined space to fit my project into.
Would it be possible to introduce the headphone jack into the circuit before the amplification board? Obliviously, I don't want to amplify the headphones, just the speaker.
Your help is very much appreciated.