You can find more of James’ tutorials at makemorenoise.org.
I just posted an update of the ValhallaFreqEcho Audio Unit, that should fix some bugs people were encountering with Logic. The plugin assumes stereo-input, stereo-output, but the older version of the AU wasn’t enforcing this. I changed the code so that it can only be instantiated on stereo tracks. I will work on having it run with mono tracks in a future release.
Download the new version of the code here.