Fellow Chuckists, "Delay" definately has a floatingpoint denormalisation issue (well, either Delay or Envelope). My feedbackloop went something like this; soundsource => Delay del => dac; del => Envelope feedback => del: .9 => feedback.gain; In this form it has to loop for quite a while before the issue shows up in cpu usage and it will probably be most evident in situations where other Ugens are also using floatingpoint opperations. A smaller value then .9 for the gain should speed up the phenomenon. In my case my "soundsource" had filled the Delay with sound, then went quiet, after some time the CPU meter rose fairly sharply, because of the controll using HID that I had over the feedback envelope I could make the CPU usage go down again with one switch, meaning I'm absolutely positive it was this loop that was to blame. This is on Windows, using the unnoficial ASIO build that Philippe posted, delay time was around one second or so, neither of which should matter that much. Kas.