• 8hp
  • Waveform selection and Frequency controls
  • Toggle switch between L,M,H freq ranges
  • Toggle switch between L,H output levels
  • CV Inputs: Frequency
  • CV Output: LFO Out

The GS1-L is a simple utility LFO module, using the design of the LFO provided by Roland within the System 100M.

The generation of the waveforms and output stage make use of the BA662 differential op amp circuit, and as discussed on the GS1-A and GS1-F pages, the BA6110 is a suitable replacement. Due to needing a rotary 5 position switch this module has to be 8hp in width, component wise it could easily be smaller. This means however there is enough room to provide footprints for either a BA662 clone or the BA6110.

The partial DIY kits come with the BA6110 op amps, as well as RC4558 op amp, all transistors and the 2P5T rotary switch.

The module makes use of the 2P5T switch, despite it being deeper than the normal pots and jacks used in Eurorack modules, by means of a mezzanine card. This also means care was needed when designing the PCBs to ensure no tall components are placed under the switch. There is on 8-pin DIP IC towards the top of the lower board, be sure not to use a socket for the IC here!

The waveforms this LFO outputs fall into two categories :

0-10v range and -5v to +5v range (p2p)

The Sine and Triangle waveforms output in the -5 to +5 range.

The Square, Ramp and Sawtooth all output in the 0-10v range.

If these are too hot, you can use the toggle switch to reduce to roughly 1/10th the output voltage ranges, then use a VCA or other to boost if you need something in the middle!

The module provides LFO frequency control via the potentiometer as well as a CV input for frequency where a typical square or clock like signal can be used. There is a also a toggle switch that lets you change the frequency range, with Low, Middle and High settings. At its lowest, the LFO has a cycle time of around 2s, at its highest it doesn’t quite go into audio range.

Images to follow

GS Series 1

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