Hey, I’ve been using renoise to make music for years now and for the first time I’ve stumbled across something that’s quite annoying! This is a problem I noticed a while ago. For some Dsp effects when I right click on the check mark in order to turn on the effect I hear a pop. This was usually with 3rd party plug ins. But in a song I’m working on now I’m triggering my send channel on and off on every beat. This is creating a really bad popping noise. It took me a while to notice the sound and I thought it was coming from the samples I was working with. As soon as I deleted my send the problem stopped! Any help?
It’s probably better if you automate the Send Device’s Amount parameter instead, alternating between 0dB and -INFdB as needed. This should avoid the click/pop that you’re experiencing when turning the entire device on and off repeatedly.
from what I learned it may screw up PDC. looks like a disabled send-device excludes send-tracks DSP from PDC calculation. try without PDC or what dblue says 
K thanks guys!