2LFOSH

Dual LFO + Sample/Hold

The 2LFOSH module is a combination of three different modules on one board, designed to be easy to be easy to build and have simple, bare-bones features, making it ideal for people new to building DIY synthesizers, and those with small systems who need multiple uses from each module. It requires no calibration.

The module is composed of two low frequency oscillators (LFOs) and a sample and hold (SH) circuit. The LFOs each have a switch to change between LFO ranges and audio ranges. Technically, the correct term is "manually controlled oscillator" when it is operating at audio range, but LFO is still used commonly.

Each LFO has just two outputs, a square wave and a triangle wave. There is also a mixed triangle wave output which is the inverted sum of the two triangle wave outputs. Each LFO has an LED indicator, to visually show frequency. When design started, the original focus was on an easy to build sample and hold module. A sample and hold has two inputs, one input for the voltage to be sampled and one input for a trigger to tell it when to sample the input. It is common to see an LFO used to trigger the samples, and a noise generator used as the voltage input.

Often the noise generator is built into the same module as the sample and hold. I decided to build a second LFO into the module instead of a noise source because in my experience, it would be more useful when not using it as a voltage source for the SH than a noise source; but it would still provide voltages that were unpredictable enough for the human ear to pick up on when run at audio range with the SH trigger run at a lower frequency.

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