The Kraken is a modified Mutron Micro V™ envelope filter. The Mutron Micro V™ is the “little brother” of the more fully featured Mutron III™ having only a Range pot and a Hi/Low switch for the filtering. The Kraken expands the controls to include Attack and Decay for the envelope response. This is the only alteration to this classic and great sounding envelope!
Range: This controls the intensity of the envelope dynamics generated by your pick attack. Higher settings yield greater sensitivity, which in turn drives the intensity of the swept filter.
Attack: This control lets you dial in finer adjustments to the attack of the envelope. It is interactive with the Range pot.
Decay: This control determines how long it takes for the envelope to sweep the filter. Higher settings yield longer decay times.
Hi/Lo: This switch controls the range of the filter that is swept. Hi is thin and resonant. Lo is full and dark.
Try a pair of diodes with lower forward voltage for D1 and D2. This may improve sensitivity to picking dynamics. You can use 1n34a, BAT41 or BAT46.
Try a higher value pot for the Decay control for even longer decay times. Suggestions are 250kB or 500kB.
I can't find a vid of the Kraken and so here's the Mutron V. I will swap this for a Kraken vid when someone here verifies this and posts one for me :o)