[PD] audio problem on OSX with a particular mixer

[rene beekman]

i'm running into a strange problem with a particular mixer, a behringer dx626. I've got the headphones/lineout of my intel macbook (running os 10.6.2) connected to one of the line-ins on the mixer.

audio playback through the mixer works fine from itunes or from the finder.

when i switch to pd, however, audio keeps switching on and off at a rate of about 2 or 3 times a second.

i've tried fiddling with the Pd settings to solve this, but have not been able to find a solution so far.

i'm using portaudio, sampling rate 44100, delay 50ms, no callbacks, input and output devices are set to built-in mic & output.

changing any of these settings does not make any difference.

tonight i installed jack and this did solve the problem.
while i'm glad i've found a solution, i hate not understanding why it works.... 
anyone any suggestions or pointers? :)


thanks

rene