$5.99 $8.99
An envelope generator & LFO with roots tracing through the EMS Synthi's idiosyncratic approach, this unit advances the concept of trapezoidal function generation to offer expanded responses to incoming gates & triggers, an onboard VCA, a palette of biasing & attenuverting features, extended modulation opportunities, and macro control of timing via a single dial.
Flip the switch on the right upward for looping LFOs or downward for 1-shot envelopes (also, there's a center position for gated looping). At the output, there are two silver adjusters for shifting the output (bias) between -5V and +5V, as well as attenuating & inverting the signal, which can be used to dial in bipolar behavior or other output variations.
While the TIME SCALE dial can be turned to adjust the overall speed, the detailed adjustment is performed via the four central, black dials. The upper ON & OFF controls effectively set a duty-cycle, or the relative high vs low output times, of a pulse wave. Then, the RISE control sets the ramp-up time within the ON cycle, while the FALL control sets the ramp-down time within the FALL cycle. By the way, there's a little indicator LED that goes from blue to red when rise times exceed on times, and another one for fall/off.
This unique set of controls starts you off with pulse waves, then transforms them into triangle, saw, ramp, and all sorts of asymmetric waveforms. You can also obtain plateaus at the top with shorter rise times, or troughs at the bottom with shorter fall times. If the rise or fall exceed the on or off time, then you can clip the range. Run the output through a lowpass filter and round everything off into sine waves and other curvy mutations. Modulate all four of these controls for a broad range of evolutions.
The signal is routed to an internal VCA, amplifying input signals right at the bottom of the module. There are output gates signaling when the device is currently ON or OFF (just above the ON/OFF knobs). The GATE (or trigger) input can be used to sync LFOs or initiate envelopes and has a host of toggle buttons for various behaviors. Use SUS (sustain) to hold the ON phase beyond the dial's setting with an extended gate input. Use REL (early release) to allow the device to exit the ON phase before it's over if a gate signal goes low. The RETRIG button allows LFOs as well as envelopes to reinitiate their upward path, with an incoming pulse. The ZERO button can be turned on so that any retriggering restarts the LFOs or envelopes at 0V. Basically, you can tinker with button combos until you get the behavior you want from a gate or trigger.
Simple & deep, efficient & fully featured, utilitarian & experimental, the Trapezoidal Function Modulator is one of those utility modules that can make the boring stuff worth exploration.