AM8220 – SH02 LFO


Description The AM8220 module is faithful replica and expansion of the Low Frequency Oscillator, S&H and Noise Generator from the legendary Roland SH-2 that was released in 1979 and proved very popular with over 7,300 sold. The AM8220 is a versatile LFO that helps create the unmistakable Roland monosynth sound, in a narrow skiff friendly Eurorack module.

The original SH-2 uses an Op Amp to create a Square and Triangle from 0.2 to 25 Hz. The triangle wave is not used in the synth, but it is converted to a sine waveform with the usual delay feature (0 – 1.5 s), triggered by the keyboard. A simple Sample & Hold circuit creates a random stepped waveform from the noise generator.

Eurorack Module:    10HP wide
User Manual:             AM8220 User Manual

AMSynths Design The core of the LFO has been modified to enable voltage control and the frequency range has been retained. Below 0.2Hz the LFO stalls, so it is not possible to create very low frequencies. The triangle wave is available in addition to square delayed sine and S&H. The limited width of the PCB (38mm) means that smaller 125mW resistors have been used to ensure all the circuitry can fit onto the PCB.

There are slide potentiometers (with blue LED’s) for adjusting the LFO rate, frequency CV depth, and sine wave delay time. The delay is initiated by both a gate and trigger signal, and we recommend the AM8210 Trigger Converter module as a way to generate suitable trigger signals from the keyboard pitch. The maximum delay time has been retained at 1.5 seconds.

A 4-way rotary switch selects the output waveform; Square, Triangle Sine, Random. Each waveform has been normalised to a consistent +/-5V. There is a small slide switch to select whether the noise output is pink or white.

There are five 3.5 mm jack sockets on the front panel:

  • Gate & Trigger inputs
  • FM input
  • Noise Output
  • LFO Output

Outcome & Availability The AM8220 LFO module was developed during late August 2022 and production modules are expected to be available in October.

 

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