Klark Teknik DF 1000

... perfect for non-technicians, very narrow filters, does not alter the sound. Mounted in a church, its job does, even if I was hoping for a little quicker time. In my case, one channel to the choir mixer, one channel to the priests' microphone mixer. output to a stereo power amp, left channel for priests voice, right channel for choir mixer. Church lenght 50 meters! It works, but be careful not to exaggerate the volumes...if the LARSEN is too loud, the device is not able to stop it...and in that case you need to reduce the volume quickly, before the speakers are damaged! ! Don't wait!! For me, a good practice is to keep the volume just high enough to cause little Feedback...at which point the device works properly. When you heard the filter "kicked in", at that point you can slightly lower the volume to be even safer. What I didn't understand is if the device ALWAYS keeps the filters in its memory, even if you turn it off and on again...sometimes, when it's turned on, it behaves as if I had pressed the reset button...but this, only if I turn on with the amplifier volume very high. Overall, GREAT. It promises up to 10 db of output, I think I earned 9!!