The IF109 TGTSH (Threshold/Gate/Trigger/Sample/Hold) is a module that combines two important synthesizer functions. It produces trigger and gate signals whenever a 'timing' signal crosses a user-defined threshold. At the same time, the trigger pulse fires a high-performance sample-and-hold circuit that sampels a second 'main' signal input. The [TIMING SIGNAL] waveform would, typically, be a waveform with a -5V to +5V swing. This signal can range in frequency from around 0Hz to well over 5kHz. The triangle output from a good LFO would be a good example.

The IF 109 can be used as a regular Sample & Hold module by patching the signal to be sampled to both the [TIMING SIGNAL] and [IN] inputs. Ian Fritz says of this module, "One goal in designing this module was to be able to generate what are known as "Poincare sections" and "first return maps" in the jargon of chaos theory. In a driven system such as the IF108-ChaQuO or IF120-Chaotica circuits, this involves producing sequences of output voltages obtained by sampling the flow signals every time the driving signal crosses a particular phase value."

To demonstrate this module's operation on a chaotic system, Ian has made a short sound clip of it operating on the output of an IF108-ChaQuO module. The clip has four sections. The first section is the chaos circuit directly driving two VCO frequencies. For the following three sections the TGTSH was set up to sample the "x" output every time the "y" output crossed a threshold, and vice versa. Varying the thresholds changes the rate the pitches change and the range of pitches produced.

Build Guide