Upon Closer inspection, It's as if one unit is operating at a different input level. I can run the same signal out of slow tools, have the controls on both units exactly the same, and the unit I thought needed calibration has a hotter level on the input. It functions exactly the same as the other except due to the higher input, it causes compression to really bottom out and thus release time is much longer. I can't think of why as all componants related to the input seem to be working porperly. I might just pad the input a few DB because when I lowered the fader in Slow tools which affects the output of Slow tools, The compressor works and sounds like the other one. With threshold, compression and output level adjusts this might be the best option. I have checked the unit with 1K @+4 and +4 = )VU so that is in order... hmmmmm