Originally Posted by JasperGTR
This is the first I'm hearing about this.
What do these things do?
They delay the onset of high spring tension until just before your beater hits the head, ie you have the spring looser than normal to start with, so there is less initial resistance but as the beater approaches the head the QTC 'catches' more of the spring and ramps up the tension which provides for a quicker return.
So the pedal is easier to push on, like having loose spring tension, but still returns to starting position as fast as if it was using a higher spring tension.
It's like the red beater cam on Pearl Eliminators but used on the spring instead, and it's adjustable.