I bought a Qu-Bit Cascade sort of on a whim. Then I liked it enough to get a second one. The first one came with a large knob on the Attack pot, the second one didn’t, so I swapped it so both are large. It’s actually useful, because attack benefits from more resolution on the knob.

Cascade is a relatively new module for Qu-Bit. There is only a getting started manual. And there aren’t very many video demos yet. As is my custom, I like to investigate details of a new module and document them.

Main Features

• Four envelope generator modes, plus envelope follower and compressor modes
• Built-in high quality VCA
• Voltage-controlled ratcheting and repeating
• Voltage-controlled attack, decay, and shape
• Manual control of level, offset, and inversion of envelope
• Manually triggerable
• Self-cycling

Additional Features

• Configurable Gate output
• Four built-in sound sources
• “Gravity” options

VCA

The VCA input is normally connected to the internal sound, and the VCA CV to the envelope. These can be replaced by external signal and control for complete independent use of the VCA. It is a DC-coupled linear response VCA with unity gain at +5 volts of CV. Since the envelope out can go up to 10 volts, the VCA can amplify a signal by 2X. Set the level knob halfway to get unity gain with the envelope.

Envelope Generator Modes

Gate Output Options

• A 6ms trigger at the start of each attack
• End of Attack, defined as being low during attack
• End of Decay, defined as being low during decay

Gate output is 0/+5V. In the scope photos to follow EoD is configured, which goes HIGH at the end of a cycle.

Ratcheting AD

An Attack-Decay envelope is generated by a rising edge on the trigger input. Any wave shape works. Attack is initiated when a voltage threshold, about +0.75 volts, is crossed. Gate length is ignored.

In this ratcheting mode, the repeats knob and CV sets the number of times the envelope will re-trigger in between receipt of external triggers. But, importantly, repeats are synchronized with the external trigger so as to divide the whole interval between external triggers in to a fixed number of beats. The interval can divided by 1, 2, 3, 4, 6, 8, 12, or 16 times, resulting in that exact number of beats between external triggers.

In all envelope generator modes, if a new trigger is received before the decay phase completes, a new attack is started immediately.

Green (top trace) is the external trigger. Blue is the EoD gate output, which here indicates the start of a new cycle. Red is the envelope out. Yellow is the VCA output of the envelope applied to an external signal.

AD Mode

AD mode is just like ratcheting AD mode with one difference. Repeats are not synchronized with the incoming trigger, so that bursts can be generated. In addition, turning repeats all the way up goes into cycling mode, where no external trigger is needed.

When cycling, frequencies up to 325 Hz can be obtained.

ASR Mode

ASR Mode is exactly like AD mode, but gate length causes sustain at the top level. Self-cycling works the same way as in AD mode.

ADSR Mode

For ADSR, two knobs are repurposed. Curve sets the sustain level and Repeats sets the release time. The curve is fixed, as if the knob were centered.

Internal Sounds Demonstration

Gravity Demonstration

Gravity mean a decrease in amplitude or amplitude and time for each repeat. Gravity applies only to repeats, not to externally triggered envelopes (which confused me at first). Playing around with the two gravity settings in combination with different trigger rates, decay times, and repeat settings can yield a surprising number of interesting effects.