Kassutronics ASR Envelope Eurorack

If you’re looking for a flexible modulation source but don’t have a lot of room to spare in your Eurorack case, Caspar Ockeloen-Korppi’s Kassutronics Looping ASR module will be a perfect fit. ASR envelope generators work just like standard ADSRs, except that decay and release times are both set by the same control knob (labelled Release on this one). 

In addition to the usual Attack, Sustain, and Release controls, there’s a toggle switch that engages looping mode; this ignores the Gate input and Sustain control, allowing the module to cycle continuously through its attack and release phases. In non-looping mode, an LED indicator shows that the envelope is active, and in looping mode it blinks to indicate overall frequency.

The gate input will take a traditional Eurorack gate, or pretty much any positive-going gate ~+1.2V to +10V. In regular envelope mode, the output starts at 0V and rises to ~+7.5V; after the gate is released, output returns to 0V. Looping mode output is bipolar (like an LFO), ranging from -7.5V to +7.5V. Attack and release phases follow the usual exponential capacitor-charging curve present on traditional ADSRs.

Attack is quite snappy at the low end of the control range, measuring 1.6ms on the module we tested, with minimum release time being longer at around 4ms. Attack maxes out in the 1.2s range and release in the 3.1s range. In looping mode, attack times get longer and release times get shorter. Minimum attack time was about 1.9ms with release around 3.6ms, with both maxing out at roughly 1.6s. 

The above figures give us a cycle time range of 5.5ms~3.2s, which we measured at 0.316Hz to 172.4Hz or a 545:1 sweep range. This is about 7% better than what’s listed on the Kassutronics specification, though it may vary from module to module. Rheostat-controlled capacitor-based envelope generators have a lot of variance due to component tolerances (±20% for the potentiometers alone), so exact figures will vary from module to module. Our hope here is to give you a sense of what types of things you could do with this module in your setup!

As with many Kassutronics panel designs, this module uses a unique wooden panel with black printed labels for the controls. These are actually quite durable—neither we nor any of our customers have had an issue with one breaking, even after many years of use. That said, we’d recommend against over-torquing when installing these, so probably avoid the power drill!

Specs:

•  Size: Eurorack/4HP
•  Depth: 23mm (w/o cable)
•  Output Range: -7.5V+7.5V
•  Attack Time: 1.6ms min. 1.2s max.
•  Release Time: 4ms min. 3.1s max.
•  Frequency Range (looping mode): 1cycle/3.2s (0.33 Hz) to 172 Hz
•  Current Draw: 15mA@-12V, 15mA@+12V

This module has been tested to ensure that it works exactly as designed. Exact time ranges/frequencies will vary based on component tolerances; likewise, depth and current draw measurements are approximations intended to help with planning your Eurorack setup; please allow for additional space/current to allow for a margin of error.