Hi guys! I have an old symetrix 501 (toggle switch). It seems to have some problems. when I set fast release settings, it blocks itself, the gain reduction leds remains lit untill I turn the release knob CW. When I set fast atack settings iti distorts the signal. I have to set the atack at 10 o clock for a clean sound. The guy that sold this unit to me said this : It doesn't explain why the unit is blocking, anyway... What do tou thinK? Thank you.