Hi Fons, After our discussion in LAC I did two things : - remove some log messages - allow to better control thread priority definition, basically following the model used on Linux (server_priority = N, client_priority = N-5 so that the client may use threads with a priority between client RT value and server RT value) (see : http://comments.gmane.org/gmane.comp.audio.jackit/17931). On Windows it works like the following: - using the -P number below 89 make all RT thread takes THREAD_PRIORITY_TIME_CRITICAL priority - using value more than 89 moves in the MMCSS ("Pro Audio") class where 4 values can be used (AVRT_PRIORITY_LOW, AVRT_PRIORITY_NORMAL, AVRT_PRIORITY_HIGH, AVRT_PRIORITY_CRITICAL) - client priority is 3 below server priority: so if 92 is used for the server, then JACK server RT thread will actually takes AVRT_PRIORITY_CRITICAL and client thread will use AVRT_PRIORITY_CRITICAL - 3 = AVRT_PRIORITY_LOW - then the client my possibly use a value between AVRT_PRIORITY_LOW and AVRT_PRIORITY_CRITICAL for some other threads. Tell me it if works the way you need to, and if not, how we can improve the implementation. Links for the binaries here: https://dl.dropboxusercontent.com/u/28869550/Jack_v1.9.11_32_setup.exe https://dl.dropboxusercontent.com/u/28869550/Jack_v1.9.11_64_setup.exe Thanks. Stéphane