Dirty Dan: 3 channels of raw and snotty vactrol-based analog filter and distortion
From ST Modular comes Dirty Dan, a vactrol-based filter and distortion that pulls three channels of sound through its despicable processes. Whether you like your distortion soft or hard it’s going to get dirty.
A vactrol filter and distortion circuit? That sounds like a lot of fun. Dirty Dan has 3 inputs, the first 2 go to the filter and the third goes through a diode distortion circuit before being mixed back into the filter. You can also divert the distortion out before the filter if you want to treat that separately. You have two tonal distortion choices switching between Hard and Soft. Each input has a volume control so you can use the module as a three-channel “dirty” mixer if you wish.
You have both a high and low-pass filter hitting the high-pass first before hitting the low-pass in an unexpectedly connected way. The High-Pass knob directly influences the Cutoff. With the High-Pass turned all the way to the left the Low-Pass acts in a classic low-pass filtery fashion. But as you increase the High-Pass knob it becomes tied into the Cutoff, blending the two filters and the Cutoff starts to act as an off-set for the High-Pass. You can control them separately via CV or both together via a separate third CV input. Lastly you have a Feedback knob that feeds audio back into the filter to add some resonance.
ST Modular are only providing this as a front panel and PCB kit and brings in some interesting possibilities. The filter is vactrol based meaning that it uses an enclosed LED and light-dependent resistor combination to control the filter. Vactrols provide a very organic feel because of the lag involved in the LED light changing and the resistor responding. But vactrols can be unruly, untrustworthy and deliciously dynamic. ST Modular suggests that you could, of course, buy proper vactrols and it will sound great but it might be a whole lot more interesting to make your own vactrols (LED + light-dependent resistor wrapped in electrical tape) and see how they effect the sound of the filter. You can also change the resistor values on the feedback circuit to adjust the range – not something you’d think of doing on a pre-assembled module. That’s very interesting.
It’s not available yet but all the details and some demo videos are up on the ST Modular website.