initial commot
correct typo and picture link error
initial commit of spice circuit file

* amplifier stage with NE5532 in single supply mode
* ac analysis with printing of amplitude & phase over frequency
initial commit of simulation results

* output voltage amplitude over frequency
* output voltage phase over frequency
added gpl-v2 license text
moved into subdirectory preparing move into raspiberrypi repository
removed
Merge branch 'master' of https://github.com/tmeissner/raspi-head
Merge branch 'master' of https://github.com/tmeissner/raspberrypi