Sound Siphon doesn’t have a built-in EQ (yet), but you can use Sound Siphon along with another application to apply EQ to all of your computer’s audio.
1. Download and install Sound Siphon (no purchase necessary). Download Sound Siphon
2. Download AU Lab from Apple. http://www.apple.com/itunes/mastered-for-itunes/
3. In Sound Siphon’s preferences select the output device you are using and enable Mute. If this output device doesn’t match the output device selected in AU Lab you will not be able to control the volume.
4. Create a new document in AU Lab with Sound Siphon as the input and Built-In audio as the output.
After you create the new document, you should hear your computer’s audio again. The audio is getting played to Sound Siphon. AU Lab is getting the audio from Sound Siphon and then playing it to your Built-In audio.
5. Add the EQ (or other effects)
6. Adjust the EQ to your liking.
7. Save AU Lab document.
Now it’s as simple as opening the document to reload the EQ and settings in AU Lab.