Overview
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!
Controls
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.
Mods
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.
Notes
You can use 16mm short pin PCB mounted pots for the Attack, Range and Decay controls.
http://www.smallbearelec.com/servlet/Detail?no=692
While other ICs may work for IC2, I strongly suggest sticking with the LM1458. It seems to handle envelope controls pretty
well. You can probably use a 4558 in a pinch. I would avoid the TL072 and similar JFET based opamps.
06.13.13 – Q2 was drawn incorrectly on the schematic (collector and emitter were swapped).
The schematic on pg.2 has been corrected to show the correct orientation. You should flip Q2
180° on the PCB (on both the fabbed and single sided versions), however this is not critical: I
have confirmed the filter works the same either way. Thanks for the catch, Scruffie!
